1057b8d25SMiguel Ojeda // SPDX-License-Identifier: Apache-2.0 OR MIT 2057b8d25SMiguel Ojeda 3753dece8SMiguel Ojeda //! A contiguous growable array type with heap-allocated contents, written 4753dece8SMiguel Ojeda //! `Vec<T>`. 5753dece8SMiguel Ojeda //! 6753dece8SMiguel Ojeda //! Vectors have *O*(1) indexing, amortized *O*(1) push (to the end) and 7753dece8SMiguel Ojeda //! *O*(1) pop (from the end). 8753dece8SMiguel Ojeda //! 9753dece8SMiguel Ojeda //! Vectors ensure they never allocate more than `isize::MAX` bytes. 10753dece8SMiguel Ojeda //! 11753dece8SMiguel Ojeda //! # Examples 12753dece8SMiguel Ojeda //! 13753dece8SMiguel Ojeda //! You can explicitly create a [`Vec`] with [`Vec::new`]: 14753dece8SMiguel Ojeda //! 15753dece8SMiguel Ojeda //! ``` 16753dece8SMiguel Ojeda //! let v: Vec<i32> = Vec::new(); 17753dece8SMiguel Ojeda //! ``` 18753dece8SMiguel Ojeda //! 19753dece8SMiguel Ojeda //! ...or by using the [`vec!`] macro: 20753dece8SMiguel Ojeda //! 21753dece8SMiguel Ojeda //! ``` 22753dece8SMiguel Ojeda //! let v: Vec<i32> = vec![]; 23753dece8SMiguel Ojeda //! 24753dece8SMiguel Ojeda //! let v = vec![1, 2, 3, 4, 5]; 25753dece8SMiguel Ojeda //! 26753dece8SMiguel Ojeda //! let v = vec![0; 10]; // ten zeroes 27753dece8SMiguel Ojeda //! ``` 28753dece8SMiguel Ojeda //! 29753dece8SMiguel Ojeda //! You can [`push`] values onto the end of a vector (which will grow the vector 30753dece8SMiguel Ojeda //! as needed): 31753dece8SMiguel Ojeda //! 32753dece8SMiguel Ojeda //! ``` 33753dece8SMiguel Ojeda //! let mut v = vec![1, 2]; 34753dece8SMiguel Ojeda //! 35753dece8SMiguel Ojeda //! v.push(3); 36753dece8SMiguel Ojeda //! ``` 37753dece8SMiguel Ojeda //! 38753dece8SMiguel Ojeda //! Popping values works in much the same way: 39753dece8SMiguel Ojeda //! 40753dece8SMiguel Ojeda //! ``` 41753dece8SMiguel Ojeda //! let mut v = vec![1, 2]; 42753dece8SMiguel Ojeda //! 43753dece8SMiguel Ojeda //! let two = v.pop(); 44753dece8SMiguel Ojeda //! ``` 45753dece8SMiguel Ojeda //! 46753dece8SMiguel Ojeda //! Vectors also support indexing (through the [`Index`] and [`IndexMut`] traits): 47753dece8SMiguel Ojeda //! 48753dece8SMiguel Ojeda //! ``` 49753dece8SMiguel Ojeda //! let mut v = vec![1, 2, 3]; 50753dece8SMiguel Ojeda //! let three = v[2]; 51753dece8SMiguel Ojeda //! v[1] = v[1] + 5; 52753dece8SMiguel Ojeda //! ``` 53753dece8SMiguel Ojeda //! 54753dece8SMiguel Ojeda //! [`push`]: Vec::push 55753dece8SMiguel Ojeda 56753dece8SMiguel Ojeda #![stable(feature = "rust1", since = "1.0.0")] 57753dece8SMiguel Ojeda 58753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 59753dece8SMiguel Ojeda use core::cmp; 60753dece8SMiguel Ojeda use core::cmp::Ordering; 61753dece8SMiguel Ojeda use core::convert::TryFrom; 62753dece8SMiguel Ojeda use core::fmt; 63753dece8SMiguel Ojeda use core::hash::{Hash, Hasher}; 64753dece8SMiguel Ojeda use core::intrinsics::{arith_offset, assume}; 65753dece8SMiguel Ojeda use core::iter; 66753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 67753dece8SMiguel Ojeda use core::iter::FromIterator; 68753dece8SMiguel Ojeda use core::marker::PhantomData; 69753dece8SMiguel Ojeda use core::mem::{self, ManuallyDrop, MaybeUninit}; 70753dece8SMiguel Ojeda use core::ops::{self, Index, IndexMut, Range, RangeBounds}; 71753dece8SMiguel Ojeda use core::ptr::{self, NonNull}; 72753dece8SMiguel Ojeda use core::slice::{self, SliceIndex}; 73753dece8SMiguel Ojeda 74753dece8SMiguel Ojeda use crate::alloc::{Allocator, Global}; 75753dece8SMiguel Ojeda use crate::borrow::{Cow, ToOwned}; 76753dece8SMiguel Ojeda use crate::boxed::Box; 77753dece8SMiguel Ojeda use crate::collections::TryReserveError; 78753dece8SMiguel Ojeda use crate::raw_vec::RawVec; 79753dece8SMiguel Ojeda 80753dece8SMiguel Ojeda #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")] 81753dece8SMiguel Ojeda pub use self::drain_filter::DrainFilter; 82753dece8SMiguel Ojeda 83753dece8SMiguel Ojeda mod drain_filter; 84753dece8SMiguel Ojeda 85753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 86753dece8SMiguel Ojeda #[stable(feature = "vec_splice", since = "1.21.0")] 87753dece8SMiguel Ojeda pub use self::splice::Splice; 88753dece8SMiguel Ojeda 89753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 90753dece8SMiguel Ojeda mod splice; 91753dece8SMiguel Ojeda 92753dece8SMiguel Ojeda #[stable(feature = "drain", since = "1.6.0")] 93753dece8SMiguel Ojeda pub use self::drain::Drain; 94753dece8SMiguel Ojeda 95753dece8SMiguel Ojeda mod drain; 96753dece8SMiguel Ojeda 97753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 98753dece8SMiguel Ojeda mod cow; 99753dece8SMiguel Ojeda 100753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 101753dece8SMiguel Ojeda pub(crate) use self::in_place_collect::AsVecIntoIter; 102753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 103753dece8SMiguel Ojeda pub use self::into_iter::IntoIter; 104753dece8SMiguel Ojeda 105753dece8SMiguel Ojeda mod into_iter; 106753dece8SMiguel Ojeda 107753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 108753dece8SMiguel Ojeda use self::is_zero::IsZero; 109753dece8SMiguel Ojeda 110753dece8SMiguel Ojeda mod is_zero; 111753dece8SMiguel Ojeda 112753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 113753dece8SMiguel Ojeda mod in_place_collect; 114753dece8SMiguel Ojeda 115753dece8SMiguel Ojeda mod partial_eq; 116753dece8SMiguel Ojeda 117753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 118753dece8SMiguel Ojeda use self::spec_from_elem::SpecFromElem; 119753dece8SMiguel Ojeda 120753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 121753dece8SMiguel Ojeda mod spec_from_elem; 122753dece8SMiguel Ojeda 123753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 124753dece8SMiguel Ojeda use self::set_len_on_drop::SetLenOnDrop; 125753dece8SMiguel Ojeda 126753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 127753dece8SMiguel Ojeda mod set_len_on_drop; 128753dece8SMiguel Ojeda 129753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 130753dece8SMiguel Ojeda use self::in_place_drop::InPlaceDrop; 131753dece8SMiguel Ojeda 132753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 133753dece8SMiguel Ojeda mod in_place_drop; 134753dece8SMiguel Ojeda 135753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 136753dece8SMiguel Ojeda use self::spec_from_iter_nested::SpecFromIterNested; 137753dece8SMiguel Ojeda 138753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 139753dece8SMiguel Ojeda mod spec_from_iter_nested; 140753dece8SMiguel Ojeda 141753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 142753dece8SMiguel Ojeda use self::spec_from_iter::SpecFromIter; 143753dece8SMiguel Ojeda 144753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 145753dece8SMiguel Ojeda mod spec_from_iter; 146753dece8SMiguel Ojeda 147753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 148753dece8SMiguel Ojeda use self::spec_extend::SpecExtend; 149753dece8SMiguel Ojeda 150753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 151753dece8SMiguel Ojeda mod spec_extend; 152753dece8SMiguel Ojeda 153753dece8SMiguel Ojeda /// A contiguous growable array type, written as `Vec<T>`, short for 'vector'. 154753dece8SMiguel Ojeda /// 155753dece8SMiguel Ojeda /// # Examples 156753dece8SMiguel Ojeda /// 157753dece8SMiguel Ojeda /// ``` 158753dece8SMiguel Ojeda /// let mut vec = Vec::new(); 159753dece8SMiguel Ojeda /// vec.push(1); 160753dece8SMiguel Ojeda /// vec.push(2); 161753dece8SMiguel Ojeda /// 162753dece8SMiguel Ojeda /// assert_eq!(vec.len(), 2); 163753dece8SMiguel Ojeda /// assert_eq!(vec[0], 1); 164753dece8SMiguel Ojeda /// 165753dece8SMiguel Ojeda /// assert_eq!(vec.pop(), Some(2)); 166753dece8SMiguel Ojeda /// assert_eq!(vec.len(), 1); 167753dece8SMiguel Ojeda /// 168753dece8SMiguel Ojeda /// vec[0] = 7; 169753dece8SMiguel Ojeda /// assert_eq!(vec[0], 7); 170753dece8SMiguel Ojeda /// 171753dece8SMiguel Ojeda /// vec.extend([1, 2, 3].iter().copied()); 172753dece8SMiguel Ojeda /// 173753dece8SMiguel Ojeda /// for x in &vec { 174753dece8SMiguel Ojeda /// println!("{x}"); 175753dece8SMiguel Ojeda /// } 176753dece8SMiguel Ojeda /// assert_eq!(vec, [7, 1, 2, 3]); 177753dece8SMiguel Ojeda /// ``` 178753dece8SMiguel Ojeda /// 179753dece8SMiguel Ojeda /// The [`vec!`] macro is provided for convenient initialization: 180753dece8SMiguel Ojeda /// 181753dece8SMiguel Ojeda /// ``` 182753dece8SMiguel Ojeda /// let mut vec1 = vec![1, 2, 3]; 183753dece8SMiguel Ojeda /// vec1.push(4); 184753dece8SMiguel Ojeda /// let vec2 = Vec::from([1, 2, 3, 4]); 185753dece8SMiguel Ojeda /// assert_eq!(vec1, vec2); 186753dece8SMiguel Ojeda /// ``` 187753dece8SMiguel Ojeda /// 188753dece8SMiguel Ojeda /// It can also initialize each element of a `Vec<T>` with a given value. 189753dece8SMiguel Ojeda /// This may be more efficient than performing allocation and initialization 190753dece8SMiguel Ojeda /// in separate steps, especially when initializing a vector of zeros: 191753dece8SMiguel Ojeda /// 192753dece8SMiguel Ojeda /// ``` 193753dece8SMiguel Ojeda /// let vec = vec![0; 5]; 194753dece8SMiguel Ojeda /// assert_eq!(vec, [0, 0, 0, 0, 0]); 195753dece8SMiguel Ojeda /// 196753dece8SMiguel Ojeda /// // The following is equivalent, but potentially slower: 197753dece8SMiguel Ojeda /// let mut vec = Vec::with_capacity(5); 198753dece8SMiguel Ojeda /// vec.resize(5, 0); 199753dece8SMiguel Ojeda /// assert_eq!(vec, [0, 0, 0, 0, 0]); 200753dece8SMiguel Ojeda /// ``` 201753dece8SMiguel Ojeda /// 202753dece8SMiguel Ojeda /// For more information, see 203753dece8SMiguel Ojeda /// [Capacity and Reallocation](#capacity-and-reallocation). 204753dece8SMiguel Ojeda /// 205753dece8SMiguel Ojeda /// Use a `Vec<T>` as an efficient stack: 206753dece8SMiguel Ojeda /// 207753dece8SMiguel Ojeda /// ``` 208753dece8SMiguel Ojeda /// let mut stack = Vec::new(); 209753dece8SMiguel Ojeda /// 210753dece8SMiguel Ojeda /// stack.push(1); 211753dece8SMiguel Ojeda /// stack.push(2); 212753dece8SMiguel Ojeda /// stack.push(3); 213753dece8SMiguel Ojeda /// 214753dece8SMiguel Ojeda /// while let Some(top) = stack.pop() { 215753dece8SMiguel Ojeda /// // Prints 3, 2, 1 216753dece8SMiguel Ojeda /// println!("{top}"); 217753dece8SMiguel Ojeda /// } 218753dece8SMiguel Ojeda /// ``` 219753dece8SMiguel Ojeda /// 220753dece8SMiguel Ojeda /// # Indexing 221753dece8SMiguel Ojeda /// 222753dece8SMiguel Ojeda /// The `Vec` type allows to access values by index, because it implements the 223753dece8SMiguel Ojeda /// [`Index`] trait. An example will be more explicit: 224753dece8SMiguel Ojeda /// 225753dece8SMiguel Ojeda /// ``` 226753dece8SMiguel Ojeda /// let v = vec![0, 2, 4, 6]; 227753dece8SMiguel Ojeda /// println!("{}", v[1]); // it will display '2' 228753dece8SMiguel Ojeda /// ``` 229753dece8SMiguel Ojeda /// 230753dece8SMiguel Ojeda /// However be careful: if you try to access an index which isn't in the `Vec`, 231753dece8SMiguel Ojeda /// your software will panic! You cannot do this: 232753dece8SMiguel Ojeda /// 233753dece8SMiguel Ojeda /// ```should_panic 234753dece8SMiguel Ojeda /// let v = vec![0, 2, 4, 6]; 235753dece8SMiguel Ojeda /// println!("{}", v[6]); // it will panic! 236753dece8SMiguel Ojeda /// ``` 237753dece8SMiguel Ojeda /// 238753dece8SMiguel Ojeda /// Use [`get`] and [`get_mut`] if you want to check whether the index is in 239753dece8SMiguel Ojeda /// the `Vec`. 240753dece8SMiguel Ojeda /// 241753dece8SMiguel Ojeda /// # Slicing 242753dece8SMiguel Ojeda /// 243753dece8SMiguel Ojeda /// A `Vec` can be mutable. On the other hand, slices are read-only objects. 244753dece8SMiguel Ojeda /// To get a [slice][prim@slice], use [`&`]. Example: 245753dece8SMiguel Ojeda /// 246753dece8SMiguel Ojeda /// ``` 247753dece8SMiguel Ojeda /// fn read_slice(slice: &[usize]) { 248753dece8SMiguel Ojeda /// // ... 249753dece8SMiguel Ojeda /// } 250753dece8SMiguel Ojeda /// 251753dece8SMiguel Ojeda /// let v = vec![0, 1]; 252753dece8SMiguel Ojeda /// read_slice(&v); 253753dece8SMiguel Ojeda /// 254753dece8SMiguel Ojeda /// // ... and that's all! 255753dece8SMiguel Ojeda /// // you can also do it like this: 256753dece8SMiguel Ojeda /// let u: &[usize] = &v; 257753dece8SMiguel Ojeda /// // or like this: 258753dece8SMiguel Ojeda /// let u: &[_] = &v; 259753dece8SMiguel Ojeda /// ``` 260753dece8SMiguel Ojeda /// 261753dece8SMiguel Ojeda /// In Rust, it's more common to pass slices as arguments rather than vectors 262753dece8SMiguel Ojeda /// when you just want to provide read access. The same goes for [`String`] and 263753dece8SMiguel Ojeda /// [`&str`]. 264753dece8SMiguel Ojeda /// 265753dece8SMiguel Ojeda /// # Capacity and reallocation 266753dece8SMiguel Ojeda /// 267753dece8SMiguel Ojeda /// The capacity of a vector is the amount of space allocated for any future 268753dece8SMiguel Ojeda /// elements that will be added onto the vector. This is not to be confused with 269753dece8SMiguel Ojeda /// the *length* of a vector, which specifies the number of actual elements 270753dece8SMiguel Ojeda /// within the vector. If a vector's length exceeds its capacity, its capacity 271753dece8SMiguel Ojeda /// will automatically be increased, but its elements will have to be 272753dece8SMiguel Ojeda /// reallocated. 273753dece8SMiguel Ojeda /// 274753dece8SMiguel Ojeda /// For example, a vector with capacity 10 and length 0 would be an empty vector 275753dece8SMiguel Ojeda /// with space for 10 more elements. Pushing 10 or fewer elements onto the 276753dece8SMiguel Ojeda /// vector will not change its capacity or cause reallocation to occur. However, 277753dece8SMiguel Ojeda /// if the vector's length is increased to 11, it will have to reallocate, which 278753dece8SMiguel Ojeda /// can be slow. For this reason, it is recommended to use [`Vec::with_capacity`] 279753dece8SMiguel Ojeda /// whenever possible to specify how big the vector is expected to get. 280753dece8SMiguel Ojeda /// 281753dece8SMiguel Ojeda /// # Guarantees 282753dece8SMiguel Ojeda /// 283753dece8SMiguel Ojeda /// Due to its incredibly fundamental nature, `Vec` makes a lot of guarantees 284753dece8SMiguel Ojeda /// about its design. This ensures that it's as low-overhead as possible in 285753dece8SMiguel Ojeda /// the general case, and can be correctly manipulated in primitive ways 286753dece8SMiguel Ojeda /// by unsafe code. Note that these guarantees refer to an unqualified `Vec<T>`. 287753dece8SMiguel Ojeda /// If additional type parameters are added (e.g., to support custom allocators), 288753dece8SMiguel Ojeda /// overriding their defaults may change the behavior. 289753dece8SMiguel Ojeda /// 290753dece8SMiguel Ojeda /// Most fundamentally, `Vec` is and always will be a (pointer, capacity, length) 291753dece8SMiguel Ojeda /// triplet. No more, no less. The order of these fields is completely 292753dece8SMiguel Ojeda /// unspecified, and you should use the appropriate methods to modify these. 293753dece8SMiguel Ojeda /// The pointer will never be null, so this type is null-pointer-optimized. 294753dece8SMiguel Ojeda /// 295753dece8SMiguel Ojeda /// However, the pointer might not actually point to allocated memory. In particular, 296753dece8SMiguel Ojeda /// if you construct a `Vec` with capacity 0 via [`Vec::new`], [`vec![]`][`vec!`], 297753dece8SMiguel Ojeda /// [`Vec::with_capacity(0)`][`Vec::with_capacity`], or by calling [`shrink_to_fit`] 298753dece8SMiguel Ojeda /// on an empty Vec, it will not allocate memory. Similarly, if you store zero-sized 299753dece8SMiguel Ojeda /// types inside a `Vec`, it will not allocate space for them. *Note that in this case 300753dece8SMiguel Ojeda /// the `Vec` might not report a [`capacity`] of 0*. `Vec` will allocate if and only 301753dece8SMiguel Ojeda /// if <code>[mem::size_of::\<T>]\() * [capacity]\() > 0</code>. In general, `Vec`'s allocation 302753dece8SMiguel Ojeda /// details are very subtle --- if you intend to allocate memory using a `Vec` 303753dece8SMiguel Ojeda /// and use it for something else (either to pass to unsafe code, or to build your 304753dece8SMiguel Ojeda /// own memory-backed collection), be sure to deallocate this memory by using 305753dece8SMiguel Ojeda /// `from_raw_parts` to recover the `Vec` and then dropping it. 306753dece8SMiguel Ojeda /// 307753dece8SMiguel Ojeda /// If a `Vec` *has* allocated memory, then the memory it points to is on the heap 308753dece8SMiguel Ojeda /// (as defined by the allocator Rust is configured to use by default), and its 309753dece8SMiguel Ojeda /// pointer points to [`len`] initialized, contiguous elements in order (what 310753dece8SMiguel Ojeda /// you would see if you coerced it to a slice), followed by <code>[capacity] - [len]</code> 311753dece8SMiguel Ojeda /// logically uninitialized, contiguous elements. 312753dece8SMiguel Ojeda /// 313753dece8SMiguel Ojeda /// A vector containing the elements `'a'` and `'b'` with capacity 4 can be 314753dece8SMiguel Ojeda /// visualized as below. The top part is the `Vec` struct, it contains a 315753dece8SMiguel Ojeda /// pointer to the head of the allocation in the heap, length and capacity. 316753dece8SMiguel Ojeda /// The bottom part is the allocation on the heap, a contiguous memory block. 317753dece8SMiguel Ojeda /// 318753dece8SMiguel Ojeda /// ```text 319753dece8SMiguel Ojeda /// ptr len capacity 320753dece8SMiguel Ojeda /// +--------+--------+--------+ 321753dece8SMiguel Ojeda /// | 0x0123 | 2 | 4 | 322753dece8SMiguel Ojeda /// +--------+--------+--------+ 323753dece8SMiguel Ojeda /// | 324753dece8SMiguel Ojeda /// v 325753dece8SMiguel Ojeda /// Heap +--------+--------+--------+--------+ 326753dece8SMiguel Ojeda /// | 'a' | 'b' | uninit | uninit | 327753dece8SMiguel Ojeda /// +--------+--------+--------+--------+ 328753dece8SMiguel Ojeda /// ``` 329753dece8SMiguel Ojeda /// 330753dece8SMiguel Ojeda /// - **uninit** represents memory that is not initialized, see [`MaybeUninit`]. 331753dece8SMiguel Ojeda /// - Note: the ABI is not stable and `Vec` makes no guarantees about its memory 332753dece8SMiguel Ojeda /// layout (including the order of fields). 333753dece8SMiguel Ojeda /// 334753dece8SMiguel Ojeda /// `Vec` will never perform a "small optimization" where elements are actually 335753dece8SMiguel Ojeda /// stored on the stack for two reasons: 336753dece8SMiguel Ojeda /// 337753dece8SMiguel Ojeda /// * It would make it more difficult for unsafe code to correctly manipulate 338753dece8SMiguel Ojeda /// a `Vec`. The contents of a `Vec` wouldn't have a stable address if it were 339753dece8SMiguel Ojeda /// only moved, and it would be more difficult to determine if a `Vec` had 340753dece8SMiguel Ojeda /// actually allocated memory. 341753dece8SMiguel Ojeda /// 342753dece8SMiguel Ojeda /// * It would penalize the general case, incurring an additional branch 343753dece8SMiguel Ojeda /// on every access. 344753dece8SMiguel Ojeda /// 345753dece8SMiguel Ojeda /// `Vec` will never automatically shrink itself, even if completely empty. This 346753dece8SMiguel Ojeda /// ensures no unnecessary allocations or deallocations occur. Emptying a `Vec` 347753dece8SMiguel Ojeda /// and then filling it back up to the same [`len`] should incur no calls to 348753dece8SMiguel Ojeda /// the allocator. If you wish to free up unused memory, use 349753dece8SMiguel Ojeda /// [`shrink_to_fit`] or [`shrink_to`]. 350753dece8SMiguel Ojeda /// 351753dece8SMiguel Ojeda /// [`push`] and [`insert`] will never (re)allocate if the reported capacity is 352753dece8SMiguel Ojeda /// sufficient. [`push`] and [`insert`] *will* (re)allocate if 353753dece8SMiguel Ojeda /// <code>[len] == [capacity]</code>. That is, the reported capacity is completely 354753dece8SMiguel Ojeda /// accurate, and can be relied on. It can even be used to manually free the memory 355753dece8SMiguel Ojeda /// allocated by a `Vec` if desired. Bulk insertion methods *may* reallocate, even 356753dece8SMiguel Ojeda /// when not necessary. 357753dece8SMiguel Ojeda /// 358753dece8SMiguel Ojeda /// `Vec` does not guarantee any particular growth strategy when reallocating 359753dece8SMiguel Ojeda /// when full, nor when [`reserve`] is called. The current strategy is basic 360753dece8SMiguel Ojeda /// and it may prove desirable to use a non-constant growth factor. Whatever 361753dece8SMiguel Ojeda /// strategy is used will of course guarantee *O*(1) amortized [`push`]. 362753dece8SMiguel Ojeda /// 363753dece8SMiguel Ojeda /// `vec![x; n]`, `vec![a, b, c, d]`, and 364753dece8SMiguel Ojeda /// [`Vec::with_capacity(n)`][`Vec::with_capacity`], will all produce a `Vec` 365753dece8SMiguel Ojeda /// with exactly the requested capacity. If <code>[len] == [capacity]</code>, 366753dece8SMiguel Ojeda /// (as is the case for the [`vec!`] macro), then a `Vec<T>` can be converted to 367753dece8SMiguel Ojeda /// and from a [`Box<[T]>`][owned slice] without reallocating or moving the elements. 368753dece8SMiguel Ojeda /// 369753dece8SMiguel Ojeda /// `Vec` will not specifically overwrite any data that is removed from it, 370753dece8SMiguel Ojeda /// but also won't specifically preserve it. Its uninitialized memory is 371753dece8SMiguel Ojeda /// scratch space that it may use however it wants. It will generally just do 372753dece8SMiguel Ojeda /// whatever is most efficient or otherwise easy to implement. Do not rely on 373753dece8SMiguel Ojeda /// removed data to be erased for security purposes. Even if you drop a `Vec`, its 374753dece8SMiguel Ojeda /// buffer may simply be reused by another allocation. Even if you zero a `Vec`'s memory 375753dece8SMiguel Ojeda /// first, that might not actually happen because the optimizer does not consider 376753dece8SMiguel Ojeda /// this a side-effect that must be preserved. There is one case which we will 377753dece8SMiguel Ojeda /// not break, however: using `unsafe` code to write to the excess capacity, 378753dece8SMiguel Ojeda /// and then increasing the length to match, is always valid. 379753dece8SMiguel Ojeda /// 380753dece8SMiguel Ojeda /// Currently, `Vec` does not guarantee the order in which elements are dropped. 381753dece8SMiguel Ojeda /// The order has changed in the past and may change again. 382753dece8SMiguel Ojeda /// 383753dece8SMiguel Ojeda /// [`get`]: ../../std/vec/struct.Vec.html#method.get 384753dece8SMiguel Ojeda /// [`get_mut`]: ../../std/vec/struct.Vec.html#method.get_mut 385753dece8SMiguel Ojeda /// [`String`]: crate::string::String 386753dece8SMiguel Ojeda /// [`&str`]: type@str 387753dece8SMiguel Ojeda /// [`shrink_to_fit`]: Vec::shrink_to_fit 388753dece8SMiguel Ojeda /// [`shrink_to`]: Vec::shrink_to 389753dece8SMiguel Ojeda /// [capacity]: Vec::capacity 390753dece8SMiguel Ojeda /// [`capacity`]: Vec::capacity 391753dece8SMiguel Ojeda /// [mem::size_of::\<T>]: core::mem::size_of 392753dece8SMiguel Ojeda /// [len]: Vec::len 393753dece8SMiguel Ojeda /// [`len`]: Vec::len 394753dece8SMiguel Ojeda /// [`push`]: Vec::push 395753dece8SMiguel Ojeda /// [`insert`]: Vec::insert 396753dece8SMiguel Ojeda /// [`reserve`]: Vec::reserve 397753dece8SMiguel Ojeda /// [`MaybeUninit`]: core::mem::MaybeUninit 398753dece8SMiguel Ojeda /// [owned slice]: Box 399753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 400753dece8SMiguel Ojeda #[cfg_attr(not(test), rustc_diagnostic_item = "Vec")] 401753dece8SMiguel Ojeda #[rustc_insignificant_dtor] 402753dece8SMiguel Ojeda pub struct Vec<T, #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global> { 403753dece8SMiguel Ojeda buf: RawVec<T, A>, 404753dece8SMiguel Ojeda len: usize, 405753dece8SMiguel Ojeda } 406753dece8SMiguel Ojeda 407753dece8SMiguel Ojeda //////////////////////////////////////////////////////////////////////////////// 408753dece8SMiguel Ojeda // Inherent methods 409753dece8SMiguel Ojeda //////////////////////////////////////////////////////////////////////////////// 410753dece8SMiguel Ojeda 411753dece8SMiguel Ojeda impl<T> Vec<T> { 412753dece8SMiguel Ojeda /// Constructs a new, empty `Vec<T>`. 413753dece8SMiguel Ojeda /// 414753dece8SMiguel Ojeda /// The vector will not allocate until elements are pushed onto it. 415753dece8SMiguel Ojeda /// 416753dece8SMiguel Ojeda /// # Examples 417753dece8SMiguel Ojeda /// 418753dece8SMiguel Ojeda /// ``` 419753dece8SMiguel Ojeda /// # #![allow(unused_mut)] 420753dece8SMiguel Ojeda /// let mut vec: Vec<i32> = Vec::new(); 421753dece8SMiguel Ojeda /// ``` 422753dece8SMiguel Ojeda #[inline] 423753dece8SMiguel Ojeda #[rustc_const_stable(feature = "const_vec_new", since = "1.39.0")] 424753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 425753dece8SMiguel Ojeda #[must_use] 426753dece8SMiguel Ojeda pub const fn new() -> Self { 427753dece8SMiguel Ojeda Vec { buf: RawVec::NEW, len: 0 } 428753dece8SMiguel Ojeda } 429753dece8SMiguel Ojeda 430753dece8SMiguel Ojeda /// Constructs a new, empty `Vec<T>` with the specified capacity. 431753dece8SMiguel Ojeda /// 432753dece8SMiguel Ojeda /// The vector will be able to hold exactly `capacity` elements without 433753dece8SMiguel Ojeda /// reallocating. If `capacity` is 0, the vector will not allocate. 434753dece8SMiguel Ojeda /// 435753dece8SMiguel Ojeda /// It is important to note that although the returned vector has the 436753dece8SMiguel Ojeda /// *capacity* specified, the vector will have a zero *length*. For an 437753dece8SMiguel Ojeda /// explanation of the difference between length and capacity, see 438753dece8SMiguel Ojeda /// *[Capacity and reallocation]*. 439753dece8SMiguel Ojeda /// 440753dece8SMiguel Ojeda /// [Capacity and reallocation]: #capacity-and-reallocation 441753dece8SMiguel Ojeda /// 442753dece8SMiguel Ojeda /// # Panics 443753dece8SMiguel Ojeda /// 444753dece8SMiguel Ojeda /// Panics if the new capacity exceeds `isize::MAX` bytes. 445753dece8SMiguel Ojeda /// 446753dece8SMiguel Ojeda /// # Examples 447753dece8SMiguel Ojeda /// 448753dece8SMiguel Ojeda /// ``` 449753dece8SMiguel Ojeda /// let mut vec = Vec::with_capacity(10); 450753dece8SMiguel Ojeda /// 451753dece8SMiguel Ojeda /// // The vector contains no items, even though it has capacity for more 452753dece8SMiguel Ojeda /// assert_eq!(vec.len(), 0); 453753dece8SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 454753dece8SMiguel Ojeda /// 455753dece8SMiguel Ojeda /// // These are all done without reallocating... 456753dece8SMiguel Ojeda /// for i in 0..10 { 457753dece8SMiguel Ojeda /// vec.push(i); 458753dece8SMiguel Ojeda /// } 459753dece8SMiguel Ojeda /// assert_eq!(vec.len(), 10); 460753dece8SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 461753dece8SMiguel Ojeda /// 462753dece8SMiguel Ojeda /// // ...but this may make the vector reallocate 463753dece8SMiguel Ojeda /// vec.push(11); 464753dece8SMiguel Ojeda /// assert_eq!(vec.len(), 11); 465753dece8SMiguel Ojeda /// assert!(vec.capacity() >= 11); 466753dece8SMiguel Ojeda /// ``` 467753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 468753dece8SMiguel Ojeda #[inline] 469753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 470753dece8SMiguel Ojeda #[must_use] 471753dece8SMiguel Ojeda pub fn with_capacity(capacity: usize) -> Self { 472753dece8SMiguel Ojeda Self::with_capacity_in(capacity, Global) 473753dece8SMiguel Ojeda } 474753dece8SMiguel Ojeda 475*feadd062SMiguel Ojeda /// Tries to construct a new, empty `Vec<T>` with the specified capacity. 476*feadd062SMiguel Ojeda /// 477*feadd062SMiguel Ojeda /// The vector will be able to hold exactly `capacity` elements without 478*feadd062SMiguel Ojeda /// reallocating. If `capacity` is 0, the vector will not allocate. 479*feadd062SMiguel Ojeda /// 480*feadd062SMiguel Ojeda /// It is important to note that although the returned vector has the 481*feadd062SMiguel Ojeda /// *capacity* specified, the vector will have a zero *length*. For an 482*feadd062SMiguel Ojeda /// explanation of the difference between length and capacity, see 483*feadd062SMiguel Ojeda /// *[Capacity and reallocation]*. 484*feadd062SMiguel Ojeda /// 485*feadd062SMiguel Ojeda /// [Capacity and reallocation]: #capacity-and-reallocation 486*feadd062SMiguel Ojeda /// 487*feadd062SMiguel Ojeda /// # Examples 488*feadd062SMiguel Ojeda /// 489*feadd062SMiguel Ojeda /// ``` 490*feadd062SMiguel Ojeda /// let mut vec = Vec::try_with_capacity(10).unwrap(); 491*feadd062SMiguel Ojeda /// 492*feadd062SMiguel Ojeda /// // The vector contains no items, even though it has capacity for more 493*feadd062SMiguel Ojeda /// assert_eq!(vec.len(), 0); 494*feadd062SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 495*feadd062SMiguel Ojeda /// 496*feadd062SMiguel Ojeda /// // These are all done without reallocating... 497*feadd062SMiguel Ojeda /// for i in 0..10 { 498*feadd062SMiguel Ojeda /// vec.push(i); 499*feadd062SMiguel Ojeda /// } 500*feadd062SMiguel Ojeda /// assert_eq!(vec.len(), 10); 501*feadd062SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 502*feadd062SMiguel Ojeda /// 503*feadd062SMiguel Ojeda /// // ...but this may make the vector reallocate 504*feadd062SMiguel Ojeda /// vec.push(11); 505*feadd062SMiguel Ojeda /// assert_eq!(vec.len(), 11); 506*feadd062SMiguel Ojeda /// assert!(vec.capacity() >= 11); 507*feadd062SMiguel Ojeda /// 508*feadd062SMiguel Ojeda /// let mut result = Vec::try_with_capacity(usize::MAX); 509*feadd062SMiguel Ojeda /// assert!(result.is_err()); 510*feadd062SMiguel Ojeda /// ``` 511*feadd062SMiguel Ojeda #[inline] 512*feadd062SMiguel Ojeda #[stable(feature = "kernel", since = "1.0.0")] 513*feadd062SMiguel Ojeda pub fn try_with_capacity(capacity: usize) -> Result<Self, TryReserveError> { 514*feadd062SMiguel Ojeda Self::try_with_capacity_in(capacity, Global) 515*feadd062SMiguel Ojeda } 516*feadd062SMiguel Ojeda 517753dece8SMiguel Ojeda /// Creates a `Vec<T>` directly from the raw components of another vector. 518753dece8SMiguel Ojeda /// 519753dece8SMiguel Ojeda /// # Safety 520753dece8SMiguel Ojeda /// 521753dece8SMiguel Ojeda /// This is highly unsafe, due to the number of invariants that aren't 522753dece8SMiguel Ojeda /// checked: 523753dece8SMiguel Ojeda /// 524753dece8SMiguel Ojeda /// * `ptr` needs to have been previously allocated via [`String`]/`Vec<T>` 525753dece8SMiguel Ojeda /// (at least, it's highly likely to be incorrect if it wasn't). 526753dece8SMiguel Ojeda /// * `T` needs to have the same alignment as what `ptr` was allocated with. 527753dece8SMiguel Ojeda /// (`T` having a less strict alignment is not sufficient, the alignment really 528753dece8SMiguel Ojeda /// needs to be equal to satisfy the [`dealloc`] requirement that memory must be 529753dece8SMiguel Ojeda /// allocated and deallocated with the same layout.) 530753dece8SMiguel Ojeda /// * The size of `T` times the `capacity` (ie. the allocated size in bytes) needs 531753dece8SMiguel Ojeda /// to be the same size as the pointer was allocated with. (Because similar to 532753dece8SMiguel Ojeda /// alignment, [`dealloc`] must be called with the same layout `size`.) 533753dece8SMiguel Ojeda /// * `length` needs to be less than or equal to `capacity`. 534753dece8SMiguel Ojeda /// 535753dece8SMiguel Ojeda /// Violating these may cause problems like corrupting the allocator's 536753dece8SMiguel Ojeda /// internal data structures. For example it is normally **not** safe 537753dece8SMiguel Ojeda /// to build a `Vec<u8>` from a pointer to a C `char` array with length 538753dece8SMiguel Ojeda /// `size_t`, doing so is only safe if the array was initially allocated by 539753dece8SMiguel Ojeda /// a `Vec` or `String`. 540753dece8SMiguel Ojeda /// It's also not safe to build one from a `Vec<u16>` and its length, because 541753dece8SMiguel Ojeda /// the allocator cares about the alignment, and these two types have different 542753dece8SMiguel Ojeda /// alignments. The buffer was allocated with alignment 2 (for `u16`), but after 543753dece8SMiguel Ojeda /// turning it into a `Vec<u8>` it'll be deallocated with alignment 1. To avoid 544753dece8SMiguel Ojeda /// these issues, it is often preferable to do casting/transmuting using 545753dece8SMiguel Ojeda /// [`slice::from_raw_parts`] instead. 546753dece8SMiguel Ojeda /// 547753dece8SMiguel Ojeda /// The ownership of `ptr` is effectively transferred to the 548753dece8SMiguel Ojeda /// `Vec<T>` which may then deallocate, reallocate or change the 549753dece8SMiguel Ojeda /// contents of memory pointed to by the pointer at will. Ensure 550753dece8SMiguel Ojeda /// that nothing else uses the pointer after calling this 551753dece8SMiguel Ojeda /// function. 552753dece8SMiguel Ojeda /// 553753dece8SMiguel Ojeda /// [`String`]: crate::string::String 554753dece8SMiguel Ojeda /// [`dealloc`]: crate::alloc::GlobalAlloc::dealloc 555753dece8SMiguel Ojeda /// 556753dece8SMiguel Ojeda /// # Examples 557753dece8SMiguel Ojeda /// 558753dece8SMiguel Ojeda /// ``` 559753dece8SMiguel Ojeda /// use std::ptr; 560753dece8SMiguel Ojeda /// use std::mem; 561753dece8SMiguel Ojeda /// 562753dece8SMiguel Ojeda /// let v = vec![1, 2, 3]; 563753dece8SMiguel Ojeda /// 564753dece8SMiguel Ojeda // FIXME Update this when vec_into_raw_parts is stabilized 565753dece8SMiguel Ojeda /// // Prevent running `v`'s destructor so we are in complete control 566753dece8SMiguel Ojeda /// // of the allocation. 567753dece8SMiguel Ojeda /// let mut v = mem::ManuallyDrop::new(v); 568753dece8SMiguel Ojeda /// 569753dece8SMiguel Ojeda /// // Pull out the various important pieces of information about `v` 570753dece8SMiguel Ojeda /// let p = v.as_mut_ptr(); 571753dece8SMiguel Ojeda /// let len = v.len(); 572753dece8SMiguel Ojeda /// let cap = v.capacity(); 573753dece8SMiguel Ojeda /// 574753dece8SMiguel Ojeda /// unsafe { 575753dece8SMiguel Ojeda /// // Overwrite memory with 4, 5, 6 576753dece8SMiguel Ojeda /// for i in 0..len as isize { 577753dece8SMiguel Ojeda /// ptr::write(p.offset(i), 4 + i); 578753dece8SMiguel Ojeda /// } 579753dece8SMiguel Ojeda /// 580753dece8SMiguel Ojeda /// // Put everything back together into a Vec 581753dece8SMiguel Ojeda /// let rebuilt = Vec::from_raw_parts(p, len, cap); 582753dece8SMiguel Ojeda /// assert_eq!(rebuilt, [4, 5, 6]); 583753dece8SMiguel Ojeda /// } 584753dece8SMiguel Ojeda /// ``` 585753dece8SMiguel Ojeda #[inline] 586753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 587753dece8SMiguel Ojeda pub unsafe fn from_raw_parts(ptr: *mut T, length: usize, capacity: usize) -> Self { 588753dece8SMiguel Ojeda unsafe { Self::from_raw_parts_in(ptr, length, capacity, Global) } 589753dece8SMiguel Ojeda } 590753dece8SMiguel Ojeda } 591753dece8SMiguel Ojeda 592753dece8SMiguel Ojeda impl<T, A: Allocator> Vec<T, A> { 593753dece8SMiguel Ojeda /// Constructs a new, empty `Vec<T, A>`. 594753dece8SMiguel Ojeda /// 595753dece8SMiguel Ojeda /// The vector will not allocate until elements are pushed onto it. 596753dece8SMiguel Ojeda /// 597753dece8SMiguel Ojeda /// # Examples 598753dece8SMiguel Ojeda /// 599753dece8SMiguel Ojeda /// ``` 600753dece8SMiguel Ojeda /// #![feature(allocator_api)] 601753dece8SMiguel Ojeda /// 602753dece8SMiguel Ojeda /// use std::alloc::System; 603753dece8SMiguel Ojeda /// 604753dece8SMiguel Ojeda /// # #[allow(unused_mut)] 605753dece8SMiguel Ojeda /// let mut vec: Vec<i32, _> = Vec::new_in(System); 606753dece8SMiguel Ojeda /// ``` 607753dece8SMiguel Ojeda #[inline] 608753dece8SMiguel Ojeda #[unstable(feature = "allocator_api", issue = "32838")] 609753dece8SMiguel Ojeda pub const fn new_in(alloc: A) -> Self { 610753dece8SMiguel Ojeda Vec { buf: RawVec::new_in(alloc), len: 0 } 611753dece8SMiguel Ojeda } 612753dece8SMiguel Ojeda 613753dece8SMiguel Ojeda /// Constructs a new, empty `Vec<T, A>` with the specified capacity with the provided 614753dece8SMiguel Ojeda /// allocator. 615753dece8SMiguel Ojeda /// 616753dece8SMiguel Ojeda /// The vector will be able to hold exactly `capacity` elements without 617753dece8SMiguel Ojeda /// reallocating. If `capacity` is 0, the vector will not allocate. 618753dece8SMiguel Ojeda /// 619753dece8SMiguel Ojeda /// It is important to note that although the returned vector has the 620753dece8SMiguel Ojeda /// *capacity* specified, the vector will have a zero *length*. For an 621753dece8SMiguel Ojeda /// explanation of the difference between length and capacity, see 622753dece8SMiguel Ojeda /// *[Capacity and reallocation]*. 623753dece8SMiguel Ojeda /// 624753dece8SMiguel Ojeda /// [Capacity and reallocation]: #capacity-and-reallocation 625753dece8SMiguel Ojeda /// 626753dece8SMiguel Ojeda /// # Panics 627753dece8SMiguel Ojeda /// 628753dece8SMiguel Ojeda /// Panics if the new capacity exceeds `isize::MAX` bytes. 629753dece8SMiguel Ojeda /// 630753dece8SMiguel Ojeda /// # Examples 631753dece8SMiguel Ojeda /// 632753dece8SMiguel Ojeda /// ``` 633753dece8SMiguel Ojeda /// #![feature(allocator_api)] 634753dece8SMiguel Ojeda /// 635753dece8SMiguel Ojeda /// use std::alloc::System; 636753dece8SMiguel Ojeda /// 637753dece8SMiguel Ojeda /// let mut vec = Vec::with_capacity_in(10, System); 638753dece8SMiguel Ojeda /// 639753dece8SMiguel Ojeda /// // The vector contains no items, even though it has capacity for more 640753dece8SMiguel Ojeda /// assert_eq!(vec.len(), 0); 641753dece8SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 642753dece8SMiguel Ojeda /// 643753dece8SMiguel Ojeda /// // These are all done without reallocating... 644753dece8SMiguel Ojeda /// for i in 0..10 { 645753dece8SMiguel Ojeda /// vec.push(i); 646753dece8SMiguel Ojeda /// } 647753dece8SMiguel Ojeda /// assert_eq!(vec.len(), 10); 648753dece8SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 649753dece8SMiguel Ojeda /// 650753dece8SMiguel Ojeda /// // ...but this may make the vector reallocate 651753dece8SMiguel Ojeda /// vec.push(11); 652753dece8SMiguel Ojeda /// assert_eq!(vec.len(), 11); 653753dece8SMiguel Ojeda /// assert!(vec.capacity() >= 11); 654753dece8SMiguel Ojeda /// ``` 655753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 656753dece8SMiguel Ojeda #[inline] 657753dece8SMiguel Ojeda #[unstable(feature = "allocator_api", issue = "32838")] 658753dece8SMiguel Ojeda pub fn with_capacity_in(capacity: usize, alloc: A) -> Self { 659753dece8SMiguel Ojeda Vec { buf: RawVec::with_capacity_in(capacity, alloc), len: 0 } 660753dece8SMiguel Ojeda } 661753dece8SMiguel Ojeda 662*feadd062SMiguel Ojeda /// Tries to construct a new, empty `Vec<T, A>` with the specified capacity 663*feadd062SMiguel Ojeda /// with the provided allocator. 664*feadd062SMiguel Ojeda /// 665*feadd062SMiguel Ojeda /// The vector will be able to hold exactly `capacity` elements without 666*feadd062SMiguel Ojeda /// reallocating. If `capacity` is 0, the vector will not allocate. 667*feadd062SMiguel Ojeda /// 668*feadd062SMiguel Ojeda /// It is important to note that although the returned vector has the 669*feadd062SMiguel Ojeda /// *capacity* specified, the vector will have a zero *length*. For an 670*feadd062SMiguel Ojeda /// explanation of the difference between length and capacity, see 671*feadd062SMiguel Ojeda /// *[Capacity and reallocation]*. 672*feadd062SMiguel Ojeda /// 673*feadd062SMiguel Ojeda /// [Capacity and reallocation]: #capacity-and-reallocation 674*feadd062SMiguel Ojeda /// 675*feadd062SMiguel Ojeda /// # Examples 676*feadd062SMiguel Ojeda /// 677*feadd062SMiguel Ojeda /// ``` 678*feadd062SMiguel Ojeda /// #![feature(allocator_api)] 679*feadd062SMiguel Ojeda /// 680*feadd062SMiguel Ojeda /// use std::alloc::System; 681*feadd062SMiguel Ojeda /// 682*feadd062SMiguel Ojeda /// let mut vec = Vec::try_with_capacity_in(10, System).unwrap(); 683*feadd062SMiguel Ojeda /// 684*feadd062SMiguel Ojeda /// // The vector contains no items, even though it has capacity for more 685*feadd062SMiguel Ojeda /// assert_eq!(vec.len(), 0); 686*feadd062SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 687*feadd062SMiguel Ojeda /// 688*feadd062SMiguel Ojeda /// // These are all done without reallocating... 689*feadd062SMiguel Ojeda /// for i in 0..10 { 690*feadd062SMiguel Ojeda /// vec.push(i); 691*feadd062SMiguel Ojeda /// } 692*feadd062SMiguel Ojeda /// assert_eq!(vec.len(), 10); 693*feadd062SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 694*feadd062SMiguel Ojeda /// 695*feadd062SMiguel Ojeda /// // ...but this may make the vector reallocate 696*feadd062SMiguel Ojeda /// vec.push(11); 697*feadd062SMiguel Ojeda /// assert_eq!(vec.len(), 11); 698*feadd062SMiguel Ojeda /// assert!(vec.capacity() >= 11); 699*feadd062SMiguel Ojeda /// 700*feadd062SMiguel Ojeda /// let mut result = Vec::try_with_capacity_in(usize::MAX, System); 701*feadd062SMiguel Ojeda /// assert!(result.is_err()); 702*feadd062SMiguel Ojeda /// ``` 703*feadd062SMiguel Ojeda #[inline] 704*feadd062SMiguel Ojeda #[stable(feature = "kernel", since = "1.0.0")] 705*feadd062SMiguel Ojeda pub fn try_with_capacity_in(capacity: usize, alloc: A) -> Result<Self, TryReserveError> { 706*feadd062SMiguel Ojeda Ok(Vec { buf: RawVec::try_with_capacity_in(capacity, alloc)?, len: 0 }) 707*feadd062SMiguel Ojeda } 708*feadd062SMiguel Ojeda 709753dece8SMiguel Ojeda /// Creates a `Vec<T, A>` directly from the raw components of another vector. 710753dece8SMiguel Ojeda /// 711753dece8SMiguel Ojeda /// # Safety 712753dece8SMiguel Ojeda /// 713753dece8SMiguel Ojeda /// This is highly unsafe, due to the number of invariants that aren't 714753dece8SMiguel Ojeda /// checked: 715753dece8SMiguel Ojeda /// 716753dece8SMiguel Ojeda /// * `ptr` needs to have been previously allocated via [`String`]/`Vec<T>` 717753dece8SMiguel Ojeda /// (at least, it's highly likely to be incorrect if it wasn't). 718753dece8SMiguel Ojeda /// * `T` needs to have the same size and alignment as what `ptr` was allocated with. 719753dece8SMiguel Ojeda /// (`T` having a less strict alignment is not sufficient, the alignment really 720753dece8SMiguel Ojeda /// needs to be equal to satisfy the [`dealloc`] requirement that memory must be 721753dece8SMiguel Ojeda /// allocated and deallocated with the same layout.) 722753dece8SMiguel Ojeda /// * `length` needs to be less than or equal to `capacity`. 723753dece8SMiguel Ojeda /// * `capacity` needs to be the capacity that the pointer was allocated with. 724753dece8SMiguel Ojeda /// 725753dece8SMiguel Ojeda /// Violating these may cause problems like corrupting the allocator's 726753dece8SMiguel Ojeda /// internal data structures. For example it is **not** safe 727753dece8SMiguel Ojeda /// to build a `Vec<u8>` from a pointer to a C `char` array with length `size_t`. 728753dece8SMiguel Ojeda /// It's also not safe to build one from a `Vec<u16>` and its length, because 729753dece8SMiguel Ojeda /// the allocator cares about the alignment, and these two types have different 730753dece8SMiguel Ojeda /// alignments. The buffer was allocated with alignment 2 (for `u16`), but after 731753dece8SMiguel Ojeda /// turning it into a `Vec<u8>` it'll be deallocated with alignment 1. 732753dece8SMiguel Ojeda /// 733753dece8SMiguel Ojeda /// The ownership of `ptr` is effectively transferred to the 734753dece8SMiguel Ojeda /// `Vec<T>` which may then deallocate, reallocate or change the 735753dece8SMiguel Ojeda /// contents of memory pointed to by the pointer at will. Ensure 736753dece8SMiguel Ojeda /// that nothing else uses the pointer after calling this 737753dece8SMiguel Ojeda /// function. 738753dece8SMiguel Ojeda /// 739753dece8SMiguel Ojeda /// [`String`]: crate::string::String 740753dece8SMiguel Ojeda /// [`dealloc`]: crate::alloc::GlobalAlloc::dealloc 741753dece8SMiguel Ojeda /// 742753dece8SMiguel Ojeda /// # Examples 743753dece8SMiguel Ojeda /// 744753dece8SMiguel Ojeda /// ``` 745753dece8SMiguel Ojeda /// #![feature(allocator_api)] 746753dece8SMiguel Ojeda /// 747753dece8SMiguel Ojeda /// use std::alloc::System; 748753dece8SMiguel Ojeda /// 749753dece8SMiguel Ojeda /// use std::ptr; 750753dece8SMiguel Ojeda /// use std::mem; 751753dece8SMiguel Ojeda /// 752753dece8SMiguel Ojeda /// let mut v = Vec::with_capacity_in(3, System); 753753dece8SMiguel Ojeda /// v.push(1); 754753dece8SMiguel Ojeda /// v.push(2); 755753dece8SMiguel Ojeda /// v.push(3); 756753dece8SMiguel Ojeda /// 757753dece8SMiguel Ojeda // FIXME Update this when vec_into_raw_parts is stabilized 758753dece8SMiguel Ojeda /// // Prevent running `v`'s destructor so we are in complete control 759753dece8SMiguel Ojeda /// // of the allocation. 760753dece8SMiguel Ojeda /// let mut v = mem::ManuallyDrop::new(v); 761753dece8SMiguel Ojeda /// 762753dece8SMiguel Ojeda /// // Pull out the various important pieces of information about `v` 763753dece8SMiguel Ojeda /// let p = v.as_mut_ptr(); 764753dece8SMiguel Ojeda /// let len = v.len(); 765753dece8SMiguel Ojeda /// let cap = v.capacity(); 766753dece8SMiguel Ojeda /// let alloc = v.allocator(); 767753dece8SMiguel Ojeda /// 768753dece8SMiguel Ojeda /// unsafe { 769753dece8SMiguel Ojeda /// // Overwrite memory with 4, 5, 6 770753dece8SMiguel Ojeda /// for i in 0..len as isize { 771753dece8SMiguel Ojeda /// ptr::write(p.offset(i), 4 + i); 772753dece8SMiguel Ojeda /// } 773753dece8SMiguel Ojeda /// 774753dece8SMiguel Ojeda /// // Put everything back together into a Vec 775753dece8SMiguel Ojeda /// let rebuilt = Vec::from_raw_parts_in(p, len, cap, alloc.clone()); 776753dece8SMiguel Ojeda /// assert_eq!(rebuilt, [4, 5, 6]); 777753dece8SMiguel Ojeda /// } 778753dece8SMiguel Ojeda /// ``` 779753dece8SMiguel Ojeda #[inline] 780753dece8SMiguel Ojeda #[unstable(feature = "allocator_api", issue = "32838")] 781753dece8SMiguel Ojeda pub unsafe fn from_raw_parts_in(ptr: *mut T, length: usize, capacity: usize, alloc: A) -> Self { 782753dece8SMiguel Ojeda unsafe { Vec { buf: RawVec::from_raw_parts_in(ptr, capacity, alloc), len: length } } 783753dece8SMiguel Ojeda } 784753dece8SMiguel Ojeda 785753dece8SMiguel Ojeda /// Decomposes a `Vec<T>` into its raw components. 786753dece8SMiguel Ojeda /// 787753dece8SMiguel Ojeda /// Returns the raw pointer to the underlying data, the length of 788753dece8SMiguel Ojeda /// the vector (in elements), and the allocated capacity of the 789753dece8SMiguel Ojeda /// data (in elements). These are the same arguments in the same 790753dece8SMiguel Ojeda /// order as the arguments to [`from_raw_parts`]. 791753dece8SMiguel Ojeda /// 792753dece8SMiguel Ojeda /// After calling this function, the caller is responsible for the 793753dece8SMiguel Ojeda /// memory previously managed by the `Vec`. The only way to do 794753dece8SMiguel Ojeda /// this is to convert the raw pointer, length, and capacity back 795753dece8SMiguel Ojeda /// into a `Vec` with the [`from_raw_parts`] function, allowing 796753dece8SMiguel Ojeda /// the destructor to perform the cleanup. 797753dece8SMiguel Ojeda /// 798753dece8SMiguel Ojeda /// [`from_raw_parts`]: Vec::from_raw_parts 799753dece8SMiguel Ojeda /// 800753dece8SMiguel Ojeda /// # Examples 801753dece8SMiguel Ojeda /// 802753dece8SMiguel Ojeda /// ``` 803753dece8SMiguel Ojeda /// #![feature(vec_into_raw_parts)] 804753dece8SMiguel Ojeda /// let v: Vec<i32> = vec![-1, 0, 1]; 805753dece8SMiguel Ojeda /// 806753dece8SMiguel Ojeda /// let (ptr, len, cap) = v.into_raw_parts(); 807753dece8SMiguel Ojeda /// 808753dece8SMiguel Ojeda /// let rebuilt = unsafe { 809753dece8SMiguel Ojeda /// // We can now make changes to the components, such as 810753dece8SMiguel Ojeda /// // transmuting the raw pointer to a compatible type. 811753dece8SMiguel Ojeda /// let ptr = ptr as *mut u32; 812753dece8SMiguel Ojeda /// 813753dece8SMiguel Ojeda /// Vec::from_raw_parts(ptr, len, cap) 814753dece8SMiguel Ojeda /// }; 815753dece8SMiguel Ojeda /// assert_eq!(rebuilt, [4294967295, 0, 1]); 816753dece8SMiguel Ojeda /// ``` 817753dece8SMiguel Ojeda #[unstable(feature = "vec_into_raw_parts", reason = "new API", issue = "65816")] 818753dece8SMiguel Ojeda pub fn into_raw_parts(self) -> (*mut T, usize, usize) { 819753dece8SMiguel Ojeda let mut me = ManuallyDrop::new(self); 820753dece8SMiguel Ojeda (me.as_mut_ptr(), me.len(), me.capacity()) 821753dece8SMiguel Ojeda } 822753dece8SMiguel Ojeda 823753dece8SMiguel Ojeda /// Decomposes a `Vec<T>` into its raw components. 824753dece8SMiguel Ojeda /// 825753dece8SMiguel Ojeda /// Returns the raw pointer to the underlying data, the length of the vector (in elements), 826753dece8SMiguel Ojeda /// the allocated capacity of the data (in elements), and the allocator. These are the same 827753dece8SMiguel Ojeda /// arguments in the same order as the arguments to [`from_raw_parts_in`]. 828753dece8SMiguel Ojeda /// 829753dece8SMiguel Ojeda /// After calling this function, the caller is responsible for the 830753dece8SMiguel Ojeda /// memory previously managed by the `Vec`. The only way to do 831753dece8SMiguel Ojeda /// this is to convert the raw pointer, length, and capacity back 832753dece8SMiguel Ojeda /// into a `Vec` with the [`from_raw_parts_in`] function, allowing 833753dece8SMiguel Ojeda /// the destructor to perform the cleanup. 834753dece8SMiguel Ojeda /// 835753dece8SMiguel Ojeda /// [`from_raw_parts_in`]: Vec::from_raw_parts_in 836753dece8SMiguel Ojeda /// 837753dece8SMiguel Ojeda /// # Examples 838753dece8SMiguel Ojeda /// 839753dece8SMiguel Ojeda /// ``` 840753dece8SMiguel Ojeda /// #![feature(allocator_api, vec_into_raw_parts)] 841753dece8SMiguel Ojeda /// 842753dece8SMiguel Ojeda /// use std::alloc::System; 843753dece8SMiguel Ojeda /// 844753dece8SMiguel Ojeda /// let mut v: Vec<i32, System> = Vec::new_in(System); 845753dece8SMiguel Ojeda /// v.push(-1); 846753dece8SMiguel Ojeda /// v.push(0); 847753dece8SMiguel Ojeda /// v.push(1); 848753dece8SMiguel Ojeda /// 849753dece8SMiguel Ojeda /// let (ptr, len, cap, alloc) = v.into_raw_parts_with_alloc(); 850753dece8SMiguel Ojeda /// 851753dece8SMiguel Ojeda /// let rebuilt = unsafe { 852753dece8SMiguel Ojeda /// // We can now make changes to the components, such as 853753dece8SMiguel Ojeda /// // transmuting the raw pointer to a compatible type. 854753dece8SMiguel Ojeda /// let ptr = ptr as *mut u32; 855753dece8SMiguel Ojeda /// 856753dece8SMiguel Ojeda /// Vec::from_raw_parts_in(ptr, len, cap, alloc) 857753dece8SMiguel Ojeda /// }; 858753dece8SMiguel Ojeda /// assert_eq!(rebuilt, [4294967295, 0, 1]); 859753dece8SMiguel Ojeda /// ``` 860753dece8SMiguel Ojeda #[unstable(feature = "allocator_api", issue = "32838")] 861753dece8SMiguel Ojeda // #[unstable(feature = "vec_into_raw_parts", reason = "new API", issue = "65816")] 862753dece8SMiguel Ojeda pub fn into_raw_parts_with_alloc(self) -> (*mut T, usize, usize, A) { 863753dece8SMiguel Ojeda let mut me = ManuallyDrop::new(self); 864753dece8SMiguel Ojeda let len = me.len(); 865753dece8SMiguel Ojeda let capacity = me.capacity(); 866753dece8SMiguel Ojeda let ptr = me.as_mut_ptr(); 867753dece8SMiguel Ojeda let alloc = unsafe { ptr::read(me.allocator()) }; 868753dece8SMiguel Ojeda (ptr, len, capacity, alloc) 869753dece8SMiguel Ojeda } 870753dece8SMiguel Ojeda 871753dece8SMiguel Ojeda /// Returns the number of elements the vector can hold without 872753dece8SMiguel Ojeda /// reallocating. 873753dece8SMiguel Ojeda /// 874753dece8SMiguel Ojeda /// # Examples 875753dece8SMiguel Ojeda /// 876753dece8SMiguel Ojeda /// ``` 877753dece8SMiguel Ojeda /// let vec: Vec<i32> = Vec::with_capacity(10); 878753dece8SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 879753dece8SMiguel Ojeda /// ``` 880753dece8SMiguel Ojeda #[inline] 881753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 882753dece8SMiguel Ojeda pub fn capacity(&self) -> usize { 883753dece8SMiguel Ojeda self.buf.capacity() 884753dece8SMiguel Ojeda } 885753dece8SMiguel Ojeda 886753dece8SMiguel Ojeda /// Reserves capacity for at least `additional` more elements to be inserted 887753dece8SMiguel Ojeda /// in the given `Vec<T>`. The collection may reserve more space to avoid 888753dece8SMiguel Ojeda /// frequent reallocations. After calling `reserve`, capacity will be 889753dece8SMiguel Ojeda /// greater than or equal to `self.len() + additional`. Does nothing if 890753dece8SMiguel Ojeda /// capacity is already sufficient. 891753dece8SMiguel Ojeda /// 892753dece8SMiguel Ojeda /// # Panics 893753dece8SMiguel Ojeda /// 894753dece8SMiguel Ojeda /// Panics if the new capacity exceeds `isize::MAX` bytes. 895753dece8SMiguel Ojeda /// 896753dece8SMiguel Ojeda /// # Examples 897753dece8SMiguel Ojeda /// 898753dece8SMiguel Ojeda /// ``` 899753dece8SMiguel Ojeda /// let mut vec = vec![1]; 900753dece8SMiguel Ojeda /// vec.reserve(10); 901753dece8SMiguel Ojeda /// assert!(vec.capacity() >= 11); 902753dece8SMiguel Ojeda /// ``` 903753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 904753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 905753dece8SMiguel Ojeda pub fn reserve(&mut self, additional: usize) { 906753dece8SMiguel Ojeda self.buf.reserve(self.len, additional); 907753dece8SMiguel Ojeda } 908753dece8SMiguel Ojeda 909753dece8SMiguel Ojeda /// Reserves the minimum capacity for exactly `additional` more elements to 910753dece8SMiguel Ojeda /// be inserted in the given `Vec<T>`. After calling `reserve_exact`, 911753dece8SMiguel Ojeda /// capacity will be greater than or equal to `self.len() + additional`. 912753dece8SMiguel Ojeda /// Does nothing if the capacity is already sufficient. 913753dece8SMiguel Ojeda /// 914753dece8SMiguel Ojeda /// Note that the allocator may give the collection more space than it 915753dece8SMiguel Ojeda /// requests. Therefore, capacity can not be relied upon to be precisely 916753dece8SMiguel Ojeda /// minimal. Prefer [`reserve`] if future insertions are expected. 917753dece8SMiguel Ojeda /// 918753dece8SMiguel Ojeda /// [`reserve`]: Vec::reserve 919753dece8SMiguel Ojeda /// 920753dece8SMiguel Ojeda /// # Panics 921753dece8SMiguel Ojeda /// 922753dece8SMiguel Ojeda /// Panics if the new capacity exceeds `isize::MAX` bytes. 923753dece8SMiguel Ojeda /// 924753dece8SMiguel Ojeda /// # Examples 925753dece8SMiguel Ojeda /// 926753dece8SMiguel Ojeda /// ``` 927753dece8SMiguel Ojeda /// let mut vec = vec![1]; 928753dece8SMiguel Ojeda /// vec.reserve_exact(10); 929753dece8SMiguel Ojeda /// assert!(vec.capacity() >= 11); 930753dece8SMiguel Ojeda /// ``` 931753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 932753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 933753dece8SMiguel Ojeda pub fn reserve_exact(&mut self, additional: usize) { 934753dece8SMiguel Ojeda self.buf.reserve_exact(self.len, additional); 935753dece8SMiguel Ojeda } 936753dece8SMiguel Ojeda 937753dece8SMiguel Ojeda /// Tries to reserve capacity for at least `additional` more elements to be inserted 938753dece8SMiguel Ojeda /// in the given `Vec<T>`. The collection may reserve more space to avoid 939753dece8SMiguel Ojeda /// frequent reallocations. After calling `try_reserve`, capacity will be 940753dece8SMiguel Ojeda /// greater than or equal to `self.len() + additional`. Does nothing if 941753dece8SMiguel Ojeda /// capacity is already sufficient. 942753dece8SMiguel Ojeda /// 943753dece8SMiguel Ojeda /// # Errors 944753dece8SMiguel Ojeda /// 945753dece8SMiguel Ojeda /// If the capacity overflows, or the allocator reports a failure, then an error 946753dece8SMiguel Ojeda /// is returned. 947753dece8SMiguel Ojeda /// 948753dece8SMiguel Ojeda /// # Examples 949753dece8SMiguel Ojeda /// 950753dece8SMiguel Ojeda /// ``` 951753dece8SMiguel Ojeda /// use std::collections::TryReserveError; 952753dece8SMiguel Ojeda /// 953753dece8SMiguel Ojeda /// fn process_data(data: &[u32]) -> Result<Vec<u32>, TryReserveError> { 954753dece8SMiguel Ojeda /// let mut output = Vec::new(); 955753dece8SMiguel Ojeda /// 956753dece8SMiguel Ojeda /// // Pre-reserve the memory, exiting if we can't 957753dece8SMiguel Ojeda /// output.try_reserve(data.len())?; 958753dece8SMiguel Ojeda /// 959753dece8SMiguel Ojeda /// // Now we know this can't OOM in the middle of our complex work 960753dece8SMiguel Ojeda /// output.extend(data.iter().map(|&val| { 961753dece8SMiguel Ojeda /// val * 2 + 5 // very complicated 962753dece8SMiguel Ojeda /// })); 963753dece8SMiguel Ojeda /// 964753dece8SMiguel Ojeda /// Ok(output) 965753dece8SMiguel Ojeda /// } 966753dece8SMiguel Ojeda /// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?"); 967753dece8SMiguel Ojeda /// ``` 968753dece8SMiguel Ojeda #[stable(feature = "try_reserve", since = "1.57.0")] 969753dece8SMiguel Ojeda pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> { 970753dece8SMiguel Ojeda self.buf.try_reserve(self.len, additional) 971753dece8SMiguel Ojeda } 972753dece8SMiguel Ojeda 973753dece8SMiguel Ojeda /// Tries to reserve the minimum capacity for exactly `additional` 974753dece8SMiguel Ojeda /// elements to be inserted in the given `Vec<T>`. After calling 975753dece8SMiguel Ojeda /// `try_reserve_exact`, capacity will be greater than or equal to 976753dece8SMiguel Ojeda /// `self.len() + additional` if it returns `Ok(())`. 977753dece8SMiguel Ojeda /// Does nothing if the capacity is already sufficient. 978753dece8SMiguel Ojeda /// 979753dece8SMiguel Ojeda /// Note that the allocator may give the collection more space than it 980753dece8SMiguel Ojeda /// requests. Therefore, capacity can not be relied upon to be precisely 981753dece8SMiguel Ojeda /// minimal. Prefer [`try_reserve`] if future insertions are expected. 982753dece8SMiguel Ojeda /// 983753dece8SMiguel Ojeda /// [`try_reserve`]: Vec::try_reserve 984753dece8SMiguel Ojeda /// 985753dece8SMiguel Ojeda /// # Errors 986753dece8SMiguel Ojeda /// 987753dece8SMiguel Ojeda /// If the capacity overflows, or the allocator reports a failure, then an error 988753dece8SMiguel Ojeda /// is returned. 989753dece8SMiguel Ojeda /// 990753dece8SMiguel Ojeda /// # Examples 991753dece8SMiguel Ojeda /// 992753dece8SMiguel Ojeda /// ``` 993753dece8SMiguel Ojeda /// use std::collections::TryReserveError; 994753dece8SMiguel Ojeda /// 995753dece8SMiguel Ojeda /// fn process_data(data: &[u32]) -> Result<Vec<u32>, TryReserveError> { 996753dece8SMiguel Ojeda /// let mut output = Vec::new(); 997753dece8SMiguel Ojeda /// 998753dece8SMiguel Ojeda /// // Pre-reserve the memory, exiting if we can't 999753dece8SMiguel Ojeda /// output.try_reserve_exact(data.len())?; 1000753dece8SMiguel Ojeda /// 1001753dece8SMiguel Ojeda /// // Now we know this can't OOM in the middle of our complex work 1002753dece8SMiguel Ojeda /// output.extend(data.iter().map(|&val| { 1003753dece8SMiguel Ojeda /// val * 2 + 5 // very complicated 1004753dece8SMiguel Ojeda /// })); 1005753dece8SMiguel Ojeda /// 1006753dece8SMiguel Ojeda /// Ok(output) 1007753dece8SMiguel Ojeda /// } 1008753dece8SMiguel Ojeda /// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?"); 1009753dece8SMiguel Ojeda /// ``` 1010753dece8SMiguel Ojeda #[stable(feature = "try_reserve", since = "1.57.0")] 1011753dece8SMiguel Ojeda pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> { 1012753dece8SMiguel Ojeda self.buf.try_reserve_exact(self.len, additional) 1013753dece8SMiguel Ojeda } 1014753dece8SMiguel Ojeda 1015753dece8SMiguel Ojeda /// Shrinks the capacity of the vector as much as possible. 1016753dece8SMiguel Ojeda /// 1017753dece8SMiguel Ojeda /// It will drop down as close as possible to the length but the allocator 1018753dece8SMiguel Ojeda /// may still inform the vector that there is space for a few more elements. 1019753dece8SMiguel Ojeda /// 1020753dece8SMiguel Ojeda /// # Examples 1021753dece8SMiguel Ojeda /// 1022753dece8SMiguel Ojeda /// ``` 1023753dece8SMiguel Ojeda /// let mut vec = Vec::with_capacity(10); 1024753dece8SMiguel Ojeda /// vec.extend([1, 2, 3]); 1025753dece8SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 1026753dece8SMiguel Ojeda /// vec.shrink_to_fit(); 1027753dece8SMiguel Ojeda /// assert!(vec.capacity() >= 3); 1028753dece8SMiguel Ojeda /// ``` 1029753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 1030753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1031753dece8SMiguel Ojeda pub fn shrink_to_fit(&mut self) { 1032753dece8SMiguel Ojeda // The capacity is never less than the length, and there's nothing to do when 1033753dece8SMiguel Ojeda // they are equal, so we can avoid the panic case in `RawVec::shrink_to_fit` 1034753dece8SMiguel Ojeda // by only calling it with a greater capacity. 1035753dece8SMiguel Ojeda if self.capacity() > self.len { 1036753dece8SMiguel Ojeda self.buf.shrink_to_fit(self.len); 1037753dece8SMiguel Ojeda } 1038753dece8SMiguel Ojeda } 1039753dece8SMiguel Ojeda 1040753dece8SMiguel Ojeda /// Shrinks the capacity of the vector with a lower bound. 1041753dece8SMiguel Ojeda /// 1042753dece8SMiguel Ojeda /// The capacity will remain at least as large as both the length 1043753dece8SMiguel Ojeda /// and the supplied value. 1044753dece8SMiguel Ojeda /// 1045753dece8SMiguel Ojeda /// If the current capacity is less than the lower limit, this is a no-op. 1046753dece8SMiguel Ojeda /// 1047753dece8SMiguel Ojeda /// # Examples 1048753dece8SMiguel Ojeda /// 1049753dece8SMiguel Ojeda /// ``` 1050753dece8SMiguel Ojeda /// let mut vec = Vec::with_capacity(10); 1051753dece8SMiguel Ojeda /// vec.extend([1, 2, 3]); 1052753dece8SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 1053753dece8SMiguel Ojeda /// vec.shrink_to(4); 1054753dece8SMiguel Ojeda /// assert!(vec.capacity() >= 4); 1055753dece8SMiguel Ojeda /// vec.shrink_to(0); 1056753dece8SMiguel Ojeda /// assert!(vec.capacity() >= 3); 1057753dece8SMiguel Ojeda /// ``` 1058753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 1059753dece8SMiguel Ojeda #[stable(feature = "shrink_to", since = "1.56.0")] 1060753dece8SMiguel Ojeda pub fn shrink_to(&mut self, min_capacity: usize) { 1061753dece8SMiguel Ojeda if self.capacity() > min_capacity { 1062753dece8SMiguel Ojeda self.buf.shrink_to_fit(cmp::max(self.len, min_capacity)); 1063753dece8SMiguel Ojeda } 1064753dece8SMiguel Ojeda } 1065753dece8SMiguel Ojeda 1066753dece8SMiguel Ojeda /// Converts the vector into [`Box<[T]>`][owned slice]. 1067753dece8SMiguel Ojeda /// 1068753dece8SMiguel Ojeda /// Note that this will drop any excess capacity. 1069753dece8SMiguel Ojeda /// 1070753dece8SMiguel Ojeda /// [owned slice]: Box 1071753dece8SMiguel Ojeda /// 1072753dece8SMiguel Ojeda /// # Examples 1073753dece8SMiguel Ojeda /// 1074753dece8SMiguel Ojeda /// ``` 1075753dece8SMiguel Ojeda /// let v = vec![1, 2, 3]; 1076753dece8SMiguel Ojeda /// 1077753dece8SMiguel Ojeda /// let slice = v.into_boxed_slice(); 1078753dece8SMiguel Ojeda /// ``` 1079753dece8SMiguel Ojeda /// 1080753dece8SMiguel Ojeda /// Any excess capacity is removed: 1081753dece8SMiguel Ojeda /// 1082753dece8SMiguel Ojeda /// ``` 1083753dece8SMiguel Ojeda /// let mut vec = Vec::with_capacity(10); 1084753dece8SMiguel Ojeda /// vec.extend([1, 2, 3]); 1085753dece8SMiguel Ojeda /// 1086753dece8SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 1087753dece8SMiguel Ojeda /// let slice = vec.into_boxed_slice(); 1088753dece8SMiguel Ojeda /// assert_eq!(slice.into_vec().capacity(), 3); 1089753dece8SMiguel Ojeda /// ``` 1090753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 1091753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1092753dece8SMiguel Ojeda pub fn into_boxed_slice(mut self) -> Box<[T], A> { 1093753dece8SMiguel Ojeda unsafe { 1094753dece8SMiguel Ojeda self.shrink_to_fit(); 1095753dece8SMiguel Ojeda let me = ManuallyDrop::new(self); 1096753dece8SMiguel Ojeda let buf = ptr::read(&me.buf); 1097753dece8SMiguel Ojeda let len = me.len(); 1098753dece8SMiguel Ojeda buf.into_box(len).assume_init() 1099753dece8SMiguel Ojeda } 1100753dece8SMiguel Ojeda } 1101753dece8SMiguel Ojeda 1102753dece8SMiguel Ojeda /// Shortens the vector, keeping the first `len` elements and dropping 1103753dece8SMiguel Ojeda /// the rest. 1104753dece8SMiguel Ojeda /// 1105753dece8SMiguel Ojeda /// If `len` is greater than the vector's current length, this has no 1106753dece8SMiguel Ojeda /// effect. 1107753dece8SMiguel Ojeda /// 1108753dece8SMiguel Ojeda /// The [`drain`] method can emulate `truncate`, but causes the excess 1109753dece8SMiguel Ojeda /// elements to be returned instead of dropped. 1110753dece8SMiguel Ojeda /// 1111753dece8SMiguel Ojeda /// Note that this method has no effect on the allocated capacity 1112753dece8SMiguel Ojeda /// of the vector. 1113753dece8SMiguel Ojeda /// 1114753dece8SMiguel Ojeda /// # Examples 1115753dece8SMiguel Ojeda /// 1116753dece8SMiguel Ojeda /// Truncating a five element vector to two elements: 1117753dece8SMiguel Ojeda /// 1118753dece8SMiguel Ojeda /// ``` 1119753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3, 4, 5]; 1120753dece8SMiguel Ojeda /// vec.truncate(2); 1121753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2]); 1122753dece8SMiguel Ojeda /// ``` 1123753dece8SMiguel Ojeda /// 1124753dece8SMiguel Ojeda /// No truncation occurs when `len` is greater than the vector's current 1125753dece8SMiguel Ojeda /// length: 1126753dece8SMiguel Ojeda /// 1127753dece8SMiguel Ojeda /// ``` 1128753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3]; 1129753dece8SMiguel Ojeda /// vec.truncate(8); 1130753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2, 3]); 1131753dece8SMiguel Ojeda /// ``` 1132753dece8SMiguel Ojeda /// 1133753dece8SMiguel Ojeda /// Truncating when `len == 0` is equivalent to calling the [`clear`] 1134753dece8SMiguel Ojeda /// method. 1135753dece8SMiguel Ojeda /// 1136753dece8SMiguel Ojeda /// ``` 1137753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3]; 1138753dece8SMiguel Ojeda /// vec.truncate(0); 1139753dece8SMiguel Ojeda /// assert_eq!(vec, []); 1140753dece8SMiguel Ojeda /// ``` 1141753dece8SMiguel Ojeda /// 1142753dece8SMiguel Ojeda /// [`clear`]: Vec::clear 1143753dece8SMiguel Ojeda /// [`drain`]: Vec::drain 1144753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1145753dece8SMiguel Ojeda pub fn truncate(&mut self, len: usize) { 1146753dece8SMiguel Ojeda // This is safe because: 1147753dece8SMiguel Ojeda // 1148753dece8SMiguel Ojeda // * the slice passed to `drop_in_place` is valid; the `len > self.len` 1149753dece8SMiguel Ojeda // case avoids creating an invalid slice, and 1150753dece8SMiguel Ojeda // * the `len` of the vector is shrunk before calling `drop_in_place`, 1151753dece8SMiguel Ojeda // such that no value will be dropped twice in case `drop_in_place` 1152753dece8SMiguel Ojeda // were to panic once (if it panics twice, the program aborts). 1153753dece8SMiguel Ojeda unsafe { 1154753dece8SMiguel Ojeda // Note: It's intentional that this is `>` and not `>=`. 1155753dece8SMiguel Ojeda // Changing it to `>=` has negative performance 1156753dece8SMiguel Ojeda // implications in some cases. See #78884 for more. 1157753dece8SMiguel Ojeda if len > self.len { 1158753dece8SMiguel Ojeda return; 1159753dece8SMiguel Ojeda } 1160753dece8SMiguel Ojeda let remaining_len = self.len - len; 1161753dece8SMiguel Ojeda let s = ptr::slice_from_raw_parts_mut(self.as_mut_ptr().add(len), remaining_len); 1162753dece8SMiguel Ojeda self.len = len; 1163753dece8SMiguel Ojeda ptr::drop_in_place(s); 1164753dece8SMiguel Ojeda } 1165753dece8SMiguel Ojeda } 1166753dece8SMiguel Ojeda 1167753dece8SMiguel Ojeda /// Extracts a slice containing the entire vector. 1168753dece8SMiguel Ojeda /// 1169753dece8SMiguel Ojeda /// Equivalent to `&s[..]`. 1170753dece8SMiguel Ojeda /// 1171753dece8SMiguel Ojeda /// # Examples 1172753dece8SMiguel Ojeda /// 1173753dece8SMiguel Ojeda /// ``` 1174753dece8SMiguel Ojeda /// use std::io::{self, Write}; 1175753dece8SMiguel Ojeda /// let buffer = vec![1, 2, 3, 5, 8]; 1176753dece8SMiguel Ojeda /// io::sink().write(buffer.as_slice()).unwrap(); 1177753dece8SMiguel Ojeda /// ``` 1178753dece8SMiguel Ojeda #[inline] 1179753dece8SMiguel Ojeda #[stable(feature = "vec_as_slice", since = "1.7.0")] 1180753dece8SMiguel Ojeda pub fn as_slice(&self) -> &[T] { 1181753dece8SMiguel Ojeda self 1182753dece8SMiguel Ojeda } 1183753dece8SMiguel Ojeda 1184753dece8SMiguel Ojeda /// Extracts a mutable slice of the entire vector. 1185753dece8SMiguel Ojeda /// 1186753dece8SMiguel Ojeda /// Equivalent to `&mut s[..]`. 1187753dece8SMiguel Ojeda /// 1188753dece8SMiguel Ojeda /// # Examples 1189753dece8SMiguel Ojeda /// 1190753dece8SMiguel Ojeda /// ``` 1191753dece8SMiguel Ojeda /// use std::io::{self, Read}; 1192753dece8SMiguel Ojeda /// let mut buffer = vec![0; 3]; 1193753dece8SMiguel Ojeda /// io::repeat(0b101).read_exact(buffer.as_mut_slice()).unwrap(); 1194753dece8SMiguel Ojeda /// ``` 1195753dece8SMiguel Ojeda #[inline] 1196753dece8SMiguel Ojeda #[stable(feature = "vec_as_slice", since = "1.7.0")] 1197753dece8SMiguel Ojeda pub fn as_mut_slice(&mut self) -> &mut [T] { 1198753dece8SMiguel Ojeda self 1199753dece8SMiguel Ojeda } 1200753dece8SMiguel Ojeda 1201753dece8SMiguel Ojeda /// Returns a raw pointer to the vector's buffer. 1202753dece8SMiguel Ojeda /// 1203753dece8SMiguel Ojeda /// The caller must ensure that the vector outlives the pointer this 1204753dece8SMiguel Ojeda /// function returns, or else it will end up pointing to garbage. 1205753dece8SMiguel Ojeda /// Modifying the vector may cause its buffer to be reallocated, 1206753dece8SMiguel Ojeda /// which would also make any pointers to it invalid. 1207753dece8SMiguel Ojeda /// 1208753dece8SMiguel Ojeda /// The caller must also ensure that the memory the pointer (non-transitively) points to 1209753dece8SMiguel Ojeda /// is never written to (except inside an `UnsafeCell`) using this pointer or any pointer 1210753dece8SMiguel Ojeda /// derived from it. If you need to mutate the contents of the slice, use [`as_mut_ptr`]. 1211753dece8SMiguel Ojeda /// 1212753dece8SMiguel Ojeda /// # Examples 1213753dece8SMiguel Ojeda /// 1214753dece8SMiguel Ojeda /// ``` 1215753dece8SMiguel Ojeda /// let x = vec![1, 2, 4]; 1216753dece8SMiguel Ojeda /// let x_ptr = x.as_ptr(); 1217753dece8SMiguel Ojeda /// 1218753dece8SMiguel Ojeda /// unsafe { 1219753dece8SMiguel Ojeda /// for i in 0..x.len() { 1220753dece8SMiguel Ojeda /// assert_eq!(*x_ptr.add(i), 1 << i); 1221753dece8SMiguel Ojeda /// } 1222753dece8SMiguel Ojeda /// } 1223753dece8SMiguel Ojeda /// ``` 1224753dece8SMiguel Ojeda /// 1225753dece8SMiguel Ojeda /// [`as_mut_ptr`]: Vec::as_mut_ptr 1226753dece8SMiguel Ojeda #[stable(feature = "vec_as_ptr", since = "1.37.0")] 1227753dece8SMiguel Ojeda #[inline] 1228753dece8SMiguel Ojeda pub fn as_ptr(&self) -> *const T { 1229753dece8SMiguel Ojeda // We shadow the slice method of the same name to avoid going through 1230753dece8SMiguel Ojeda // `deref`, which creates an intermediate reference. 1231753dece8SMiguel Ojeda let ptr = self.buf.ptr(); 1232753dece8SMiguel Ojeda unsafe { 1233753dece8SMiguel Ojeda assume(!ptr.is_null()); 1234753dece8SMiguel Ojeda } 1235753dece8SMiguel Ojeda ptr 1236753dece8SMiguel Ojeda } 1237753dece8SMiguel Ojeda 1238753dece8SMiguel Ojeda /// Returns an unsafe mutable pointer to the vector's buffer. 1239753dece8SMiguel Ojeda /// 1240753dece8SMiguel Ojeda /// The caller must ensure that the vector outlives the pointer this 1241753dece8SMiguel Ojeda /// function returns, or else it will end up pointing to garbage. 1242753dece8SMiguel Ojeda /// Modifying the vector may cause its buffer to be reallocated, 1243753dece8SMiguel Ojeda /// which would also make any pointers to it invalid. 1244753dece8SMiguel Ojeda /// 1245753dece8SMiguel Ojeda /// # Examples 1246753dece8SMiguel Ojeda /// 1247753dece8SMiguel Ojeda /// ``` 1248753dece8SMiguel Ojeda /// // Allocate vector big enough for 4 elements. 1249753dece8SMiguel Ojeda /// let size = 4; 1250753dece8SMiguel Ojeda /// let mut x: Vec<i32> = Vec::with_capacity(size); 1251753dece8SMiguel Ojeda /// let x_ptr = x.as_mut_ptr(); 1252753dece8SMiguel Ojeda /// 1253753dece8SMiguel Ojeda /// // Initialize elements via raw pointer writes, then set length. 1254753dece8SMiguel Ojeda /// unsafe { 1255753dece8SMiguel Ojeda /// for i in 0..size { 1256753dece8SMiguel Ojeda /// *x_ptr.add(i) = i as i32; 1257753dece8SMiguel Ojeda /// } 1258753dece8SMiguel Ojeda /// x.set_len(size); 1259753dece8SMiguel Ojeda /// } 1260753dece8SMiguel Ojeda /// assert_eq!(&*x, &[0, 1, 2, 3]); 1261753dece8SMiguel Ojeda /// ``` 1262753dece8SMiguel Ojeda #[stable(feature = "vec_as_ptr", since = "1.37.0")] 1263753dece8SMiguel Ojeda #[inline] 1264753dece8SMiguel Ojeda pub fn as_mut_ptr(&mut self) -> *mut T { 1265753dece8SMiguel Ojeda // We shadow the slice method of the same name to avoid going through 1266753dece8SMiguel Ojeda // `deref_mut`, which creates an intermediate reference. 1267753dece8SMiguel Ojeda let ptr = self.buf.ptr(); 1268753dece8SMiguel Ojeda unsafe { 1269753dece8SMiguel Ojeda assume(!ptr.is_null()); 1270753dece8SMiguel Ojeda } 1271753dece8SMiguel Ojeda ptr 1272753dece8SMiguel Ojeda } 1273753dece8SMiguel Ojeda 1274753dece8SMiguel Ojeda /// Returns a reference to the underlying allocator. 1275753dece8SMiguel Ojeda #[unstable(feature = "allocator_api", issue = "32838")] 1276753dece8SMiguel Ojeda #[inline] 1277753dece8SMiguel Ojeda pub fn allocator(&self) -> &A { 1278753dece8SMiguel Ojeda self.buf.allocator() 1279753dece8SMiguel Ojeda } 1280753dece8SMiguel Ojeda 1281753dece8SMiguel Ojeda /// Forces the length of the vector to `new_len`. 1282753dece8SMiguel Ojeda /// 1283753dece8SMiguel Ojeda /// This is a low-level operation that maintains none of the normal 1284753dece8SMiguel Ojeda /// invariants of the type. Normally changing the length of a vector 1285753dece8SMiguel Ojeda /// is done using one of the safe operations instead, such as 1286753dece8SMiguel Ojeda /// [`truncate`], [`resize`], [`extend`], or [`clear`]. 1287753dece8SMiguel Ojeda /// 1288753dece8SMiguel Ojeda /// [`truncate`]: Vec::truncate 1289753dece8SMiguel Ojeda /// [`resize`]: Vec::resize 1290753dece8SMiguel Ojeda /// [`extend`]: Extend::extend 1291753dece8SMiguel Ojeda /// [`clear`]: Vec::clear 1292753dece8SMiguel Ojeda /// 1293753dece8SMiguel Ojeda /// # Safety 1294753dece8SMiguel Ojeda /// 1295753dece8SMiguel Ojeda /// - `new_len` must be less than or equal to [`capacity()`]. 1296753dece8SMiguel Ojeda /// - The elements at `old_len..new_len` must be initialized. 1297753dece8SMiguel Ojeda /// 1298753dece8SMiguel Ojeda /// [`capacity()`]: Vec::capacity 1299753dece8SMiguel Ojeda /// 1300753dece8SMiguel Ojeda /// # Examples 1301753dece8SMiguel Ojeda /// 1302753dece8SMiguel Ojeda /// This method can be useful for situations in which the vector 1303753dece8SMiguel Ojeda /// is serving as a buffer for other code, particularly over FFI: 1304753dece8SMiguel Ojeda /// 1305753dece8SMiguel Ojeda /// ```no_run 1306753dece8SMiguel Ojeda /// # #![allow(dead_code)] 1307753dece8SMiguel Ojeda /// # // This is just a minimal skeleton for the doc example; 1308753dece8SMiguel Ojeda /// # // don't use this as a starting point for a real library. 1309753dece8SMiguel Ojeda /// # pub struct StreamWrapper { strm: *mut std::ffi::c_void } 1310753dece8SMiguel Ojeda /// # const Z_OK: i32 = 0; 1311753dece8SMiguel Ojeda /// # extern "C" { 1312753dece8SMiguel Ojeda /// # fn deflateGetDictionary( 1313753dece8SMiguel Ojeda /// # strm: *mut std::ffi::c_void, 1314753dece8SMiguel Ojeda /// # dictionary: *mut u8, 1315753dece8SMiguel Ojeda /// # dictLength: *mut usize, 1316753dece8SMiguel Ojeda /// # ) -> i32; 1317753dece8SMiguel Ojeda /// # } 1318753dece8SMiguel Ojeda /// # impl StreamWrapper { 1319753dece8SMiguel Ojeda /// pub fn get_dictionary(&self) -> Option<Vec<u8>> { 1320753dece8SMiguel Ojeda /// // Per the FFI method's docs, "32768 bytes is always enough". 1321753dece8SMiguel Ojeda /// let mut dict = Vec::with_capacity(32_768); 1322753dece8SMiguel Ojeda /// let mut dict_length = 0; 1323753dece8SMiguel Ojeda /// // SAFETY: When `deflateGetDictionary` returns `Z_OK`, it holds that: 1324753dece8SMiguel Ojeda /// // 1. `dict_length` elements were initialized. 1325753dece8SMiguel Ojeda /// // 2. `dict_length` <= the capacity (32_768) 1326753dece8SMiguel Ojeda /// // which makes `set_len` safe to call. 1327753dece8SMiguel Ojeda /// unsafe { 1328753dece8SMiguel Ojeda /// // Make the FFI call... 1329753dece8SMiguel Ojeda /// let r = deflateGetDictionary(self.strm, dict.as_mut_ptr(), &mut dict_length); 1330753dece8SMiguel Ojeda /// if r == Z_OK { 1331753dece8SMiguel Ojeda /// // ...and update the length to what was initialized. 1332753dece8SMiguel Ojeda /// dict.set_len(dict_length); 1333753dece8SMiguel Ojeda /// Some(dict) 1334753dece8SMiguel Ojeda /// } else { 1335753dece8SMiguel Ojeda /// None 1336753dece8SMiguel Ojeda /// } 1337753dece8SMiguel Ojeda /// } 1338753dece8SMiguel Ojeda /// } 1339753dece8SMiguel Ojeda /// # } 1340753dece8SMiguel Ojeda /// ``` 1341753dece8SMiguel Ojeda /// 1342753dece8SMiguel Ojeda /// While the following example is sound, there is a memory leak since 1343753dece8SMiguel Ojeda /// the inner vectors were not freed prior to the `set_len` call: 1344753dece8SMiguel Ojeda /// 1345753dece8SMiguel Ojeda /// ``` 1346753dece8SMiguel Ojeda /// let mut vec = vec![vec![1, 0, 0], 1347753dece8SMiguel Ojeda /// vec![0, 1, 0], 1348753dece8SMiguel Ojeda /// vec![0, 0, 1]]; 1349753dece8SMiguel Ojeda /// // SAFETY: 1350753dece8SMiguel Ojeda /// // 1. `old_len..0` is empty so no elements need to be initialized. 1351753dece8SMiguel Ojeda /// // 2. `0 <= capacity` always holds whatever `capacity` is. 1352753dece8SMiguel Ojeda /// unsafe { 1353753dece8SMiguel Ojeda /// vec.set_len(0); 1354753dece8SMiguel Ojeda /// } 1355753dece8SMiguel Ojeda /// ``` 1356753dece8SMiguel Ojeda /// 1357753dece8SMiguel Ojeda /// Normally, here, one would use [`clear`] instead to correctly drop 1358753dece8SMiguel Ojeda /// the contents and thus not leak memory. 1359753dece8SMiguel Ojeda #[inline] 1360753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1361753dece8SMiguel Ojeda pub unsafe fn set_len(&mut self, new_len: usize) { 1362753dece8SMiguel Ojeda debug_assert!(new_len <= self.capacity()); 1363753dece8SMiguel Ojeda 1364753dece8SMiguel Ojeda self.len = new_len; 1365753dece8SMiguel Ojeda } 1366753dece8SMiguel Ojeda 1367753dece8SMiguel Ojeda /// Removes an element from the vector and returns it. 1368753dece8SMiguel Ojeda /// 1369753dece8SMiguel Ojeda /// The removed element is replaced by the last element of the vector. 1370753dece8SMiguel Ojeda /// 1371753dece8SMiguel Ojeda /// This does not preserve ordering, but is *O*(1). 1372753dece8SMiguel Ojeda /// If you need to preserve the element order, use [`remove`] instead. 1373753dece8SMiguel Ojeda /// 1374753dece8SMiguel Ojeda /// [`remove`]: Vec::remove 1375753dece8SMiguel Ojeda /// 1376753dece8SMiguel Ojeda /// # Panics 1377753dece8SMiguel Ojeda /// 1378753dece8SMiguel Ojeda /// Panics if `index` is out of bounds. 1379753dece8SMiguel Ojeda /// 1380753dece8SMiguel Ojeda /// # Examples 1381753dece8SMiguel Ojeda /// 1382753dece8SMiguel Ojeda /// ``` 1383753dece8SMiguel Ojeda /// let mut v = vec!["foo", "bar", "baz", "qux"]; 1384753dece8SMiguel Ojeda /// 1385753dece8SMiguel Ojeda /// assert_eq!(v.swap_remove(1), "bar"); 1386753dece8SMiguel Ojeda /// assert_eq!(v, ["foo", "qux", "baz"]); 1387753dece8SMiguel Ojeda /// 1388753dece8SMiguel Ojeda /// assert_eq!(v.swap_remove(0), "foo"); 1389753dece8SMiguel Ojeda /// assert_eq!(v, ["baz", "qux"]); 1390753dece8SMiguel Ojeda /// ``` 1391753dece8SMiguel Ojeda #[inline] 1392753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1393753dece8SMiguel Ojeda pub fn swap_remove(&mut self, index: usize) -> T { 1394753dece8SMiguel Ojeda #[cold] 1395753dece8SMiguel Ojeda #[inline(never)] 1396753dece8SMiguel Ojeda fn assert_failed(index: usize, len: usize) -> ! { 1397753dece8SMiguel Ojeda panic!("swap_remove index (is {index}) should be < len (is {len})"); 1398753dece8SMiguel Ojeda } 1399753dece8SMiguel Ojeda 1400753dece8SMiguel Ojeda let len = self.len(); 1401753dece8SMiguel Ojeda if index >= len { 1402753dece8SMiguel Ojeda assert_failed(index, len); 1403753dece8SMiguel Ojeda } 1404753dece8SMiguel Ojeda unsafe { 1405753dece8SMiguel Ojeda // We replace self[index] with the last element. Note that if the 1406753dece8SMiguel Ojeda // bounds check above succeeds there must be a last element (which 1407753dece8SMiguel Ojeda // can be self[index] itself). 1408753dece8SMiguel Ojeda let value = ptr::read(self.as_ptr().add(index)); 1409753dece8SMiguel Ojeda let base_ptr = self.as_mut_ptr(); 1410753dece8SMiguel Ojeda ptr::copy(base_ptr.add(len - 1), base_ptr.add(index), 1); 1411753dece8SMiguel Ojeda self.set_len(len - 1); 1412753dece8SMiguel Ojeda value 1413753dece8SMiguel Ojeda } 1414753dece8SMiguel Ojeda } 1415753dece8SMiguel Ojeda 1416753dece8SMiguel Ojeda /// Inserts an element at position `index` within the vector, shifting all 1417753dece8SMiguel Ojeda /// elements after it to the right. 1418753dece8SMiguel Ojeda /// 1419753dece8SMiguel Ojeda /// # Panics 1420753dece8SMiguel Ojeda /// 1421753dece8SMiguel Ojeda /// Panics if `index > len`. 1422753dece8SMiguel Ojeda /// 1423753dece8SMiguel Ojeda /// # Examples 1424753dece8SMiguel Ojeda /// 1425753dece8SMiguel Ojeda /// ``` 1426753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3]; 1427753dece8SMiguel Ojeda /// vec.insert(1, 4); 1428753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 4, 2, 3]); 1429753dece8SMiguel Ojeda /// vec.insert(4, 5); 1430753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 4, 2, 3, 5]); 1431753dece8SMiguel Ojeda /// ``` 1432753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 1433753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1434753dece8SMiguel Ojeda pub fn insert(&mut self, index: usize, element: T) { 1435753dece8SMiguel Ojeda #[cold] 1436753dece8SMiguel Ojeda #[inline(never)] 1437753dece8SMiguel Ojeda fn assert_failed(index: usize, len: usize) -> ! { 1438753dece8SMiguel Ojeda panic!("insertion index (is {index}) should be <= len (is {len})"); 1439753dece8SMiguel Ojeda } 1440753dece8SMiguel Ojeda 1441753dece8SMiguel Ojeda let len = self.len(); 1442753dece8SMiguel Ojeda if index > len { 1443753dece8SMiguel Ojeda assert_failed(index, len); 1444753dece8SMiguel Ojeda } 1445753dece8SMiguel Ojeda 1446753dece8SMiguel Ojeda // space for the new element 1447753dece8SMiguel Ojeda if len == self.buf.capacity() { 1448753dece8SMiguel Ojeda self.reserve(1); 1449753dece8SMiguel Ojeda } 1450753dece8SMiguel Ojeda 1451753dece8SMiguel Ojeda unsafe { 1452753dece8SMiguel Ojeda // infallible 1453753dece8SMiguel Ojeda // The spot to put the new value 1454753dece8SMiguel Ojeda { 1455753dece8SMiguel Ojeda let p = self.as_mut_ptr().add(index); 1456753dece8SMiguel Ojeda // Shift everything over to make space. (Duplicating the 1457753dece8SMiguel Ojeda // `index`th element into two consecutive places.) 1458753dece8SMiguel Ojeda ptr::copy(p, p.offset(1), len - index); 1459753dece8SMiguel Ojeda // Write it in, overwriting the first copy of the `index`th 1460753dece8SMiguel Ojeda // element. 1461753dece8SMiguel Ojeda ptr::write(p, element); 1462753dece8SMiguel Ojeda } 1463753dece8SMiguel Ojeda self.set_len(len + 1); 1464753dece8SMiguel Ojeda } 1465753dece8SMiguel Ojeda } 1466753dece8SMiguel Ojeda 1467753dece8SMiguel Ojeda /// Removes and returns the element at position `index` within the vector, 1468753dece8SMiguel Ojeda /// shifting all elements after it to the left. 1469753dece8SMiguel Ojeda /// 1470753dece8SMiguel Ojeda /// Note: Because this shifts over the remaining elements, it has a 1471753dece8SMiguel Ojeda /// worst-case performance of *O*(*n*). If you don't need the order of elements 1472753dece8SMiguel Ojeda /// to be preserved, use [`swap_remove`] instead. If you'd like to remove 1473753dece8SMiguel Ojeda /// elements from the beginning of the `Vec`, consider using 1474753dece8SMiguel Ojeda /// [`VecDeque::pop_front`] instead. 1475753dece8SMiguel Ojeda /// 1476753dece8SMiguel Ojeda /// [`swap_remove`]: Vec::swap_remove 1477753dece8SMiguel Ojeda /// [`VecDeque::pop_front`]: crate::collections::VecDeque::pop_front 1478753dece8SMiguel Ojeda /// 1479753dece8SMiguel Ojeda /// # Panics 1480753dece8SMiguel Ojeda /// 1481753dece8SMiguel Ojeda /// Panics if `index` is out of bounds. 1482753dece8SMiguel Ojeda /// 1483753dece8SMiguel Ojeda /// # Examples 1484753dece8SMiguel Ojeda /// 1485753dece8SMiguel Ojeda /// ``` 1486753dece8SMiguel Ojeda /// let mut v = vec![1, 2, 3]; 1487753dece8SMiguel Ojeda /// assert_eq!(v.remove(1), 2); 1488753dece8SMiguel Ojeda /// assert_eq!(v, [1, 3]); 1489753dece8SMiguel Ojeda /// ``` 1490753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1491753dece8SMiguel Ojeda #[track_caller] 1492753dece8SMiguel Ojeda pub fn remove(&mut self, index: usize) -> T { 1493753dece8SMiguel Ojeda #[cold] 1494753dece8SMiguel Ojeda #[inline(never)] 1495753dece8SMiguel Ojeda #[track_caller] 1496753dece8SMiguel Ojeda fn assert_failed(index: usize, len: usize) -> ! { 1497753dece8SMiguel Ojeda panic!("removal index (is {index}) should be < len (is {len})"); 1498753dece8SMiguel Ojeda } 1499753dece8SMiguel Ojeda 1500753dece8SMiguel Ojeda let len = self.len(); 1501753dece8SMiguel Ojeda if index >= len { 1502753dece8SMiguel Ojeda assert_failed(index, len); 1503753dece8SMiguel Ojeda } 1504753dece8SMiguel Ojeda unsafe { 1505753dece8SMiguel Ojeda // infallible 1506753dece8SMiguel Ojeda let ret; 1507753dece8SMiguel Ojeda { 1508753dece8SMiguel Ojeda // the place we are taking from. 1509753dece8SMiguel Ojeda let ptr = self.as_mut_ptr().add(index); 1510753dece8SMiguel Ojeda // copy it out, unsafely having a copy of the value on 1511753dece8SMiguel Ojeda // the stack and in the vector at the same time. 1512753dece8SMiguel Ojeda ret = ptr::read(ptr); 1513753dece8SMiguel Ojeda 1514753dece8SMiguel Ojeda // Shift everything down to fill in that spot. 1515753dece8SMiguel Ojeda ptr::copy(ptr.offset(1), ptr, len - index - 1); 1516753dece8SMiguel Ojeda } 1517753dece8SMiguel Ojeda self.set_len(len - 1); 1518753dece8SMiguel Ojeda ret 1519753dece8SMiguel Ojeda } 1520753dece8SMiguel Ojeda } 1521753dece8SMiguel Ojeda 1522753dece8SMiguel Ojeda /// Retains only the elements specified by the predicate. 1523753dece8SMiguel Ojeda /// 1524753dece8SMiguel Ojeda /// In other words, remove all elements `e` for which `f(&e)` returns `false`. 1525753dece8SMiguel Ojeda /// This method operates in place, visiting each element exactly once in the 1526753dece8SMiguel Ojeda /// original order, and preserves the order of the retained elements. 1527753dece8SMiguel Ojeda /// 1528753dece8SMiguel Ojeda /// # Examples 1529753dece8SMiguel Ojeda /// 1530753dece8SMiguel Ojeda /// ``` 1531753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3, 4]; 1532753dece8SMiguel Ojeda /// vec.retain(|&x| x % 2 == 0); 1533753dece8SMiguel Ojeda /// assert_eq!(vec, [2, 4]); 1534753dece8SMiguel Ojeda /// ``` 1535753dece8SMiguel Ojeda /// 1536753dece8SMiguel Ojeda /// Because the elements are visited exactly once in the original order, 1537753dece8SMiguel Ojeda /// external state may be used to decide which elements to keep. 1538753dece8SMiguel Ojeda /// 1539753dece8SMiguel Ojeda /// ``` 1540753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3, 4, 5]; 1541753dece8SMiguel Ojeda /// let keep = [false, true, true, false, true]; 1542753dece8SMiguel Ojeda /// let mut iter = keep.iter(); 1543753dece8SMiguel Ojeda /// vec.retain(|_| *iter.next().unwrap()); 1544753dece8SMiguel Ojeda /// assert_eq!(vec, [2, 3, 5]); 1545753dece8SMiguel Ojeda /// ``` 1546753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1547753dece8SMiguel Ojeda pub fn retain<F>(&mut self, mut f: F) 1548753dece8SMiguel Ojeda where 1549753dece8SMiguel Ojeda F: FnMut(&T) -> bool, 1550753dece8SMiguel Ojeda { 1551753dece8SMiguel Ojeda self.retain_mut(|elem| f(elem)); 1552753dece8SMiguel Ojeda } 1553753dece8SMiguel Ojeda 1554753dece8SMiguel Ojeda /// Retains only the elements specified by the predicate, passing a mutable reference to it. 1555753dece8SMiguel Ojeda /// 1556753dece8SMiguel Ojeda /// In other words, remove all elements `e` such that `f(&mut e)` returns `false`. 1557753dece8SMiguel Ojeda /// This method operates in place, visiting each element exactly once in the 1558753dece8SMiguel Ojeda /// original order, and preserves the order of the retained elements. 1559753dece8SMiguel Ojeda /// 1560753dece8SMiguel Ojeda /// # Examples 1561753dece8SMiguel Ojeda /// 1562753dece8SMiguel Ojeda /// ``` 1563753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3, 4]; 1564753dece8SMiguel Ojeda /// vec.retain_mut(|x| if *x > 3 { 1565753dece8SMiguel Ojeda /// false 1566753dece8SMiguel Ojeda /// } else { 1567753dece8SMiguel Ojeda /// *x += 1; 1568753dece8SMiguel Ojeda /// true 1569753dece8SMiguel Ojeda /// }); 1570753dece8SMiguel Ojeda /// assert_eq!(vec, [2, 3, 4]); 1571753dece8SMiguel Ojeda /// ``` 1572753dece8SMiguel Ojeda #[stable(feature = "vec_retain_mut", since = "1.61.0")] 1573753dece8SMiguel Ojeda pub fn retain_mut<F>(&mut self, mut f: F) 1574753dece8SMiguel Ojeda where 1575753dece8SMiguel Ojeda F: FnMut(&mut T) -> bool, 1576753dece8SMiguel Ojeda { 1577753dece8SMiguel Ojeda let original_len = self.len(); 1578753dece8SMiguel Ojeda // Avoid double drop if the drop guard is not executed, 1579753dece8SMiguel Ojeda // since we may make some holes during the process. 1580753dece8SMiguel Ojeda unsafe { self.set_len(0) }; 1581753dece8SMiguel Ojeda 1582753dece8SMiguel Ojeda // Vec: [Kept, Kept, Hole, Hole, Hole, Hole, Unchecked, Unchecked] 1583753dece8SMiguel Ojeda // |<- processed len ->| ^- next to check 1584753dece8SMiguel Ojeda // |<- deleted cnt ->| 1585753dece8SMiguel Ojeda // |<- original_len ->| 1586753dece8SMiguel Ojeda // Kept: Elements which predicate returns true on. 1587753dece8SMiguel Ojeda // Hole: Moved or dropped element slot. 1588753dece8SMiguel Ojeda // Unchecked: Unchecked valid elements. 1589753dece8SMiguel Ojeda // 1590753dece8SMiguel Ojeda // This drop guard will be invoked when predicate or `drop` of element panicked. 1591753dece8SMiguel Ojeda // It shifts unchecked elements to cover holes and `set_len` to the correct length. 1592753dece8SMiguel Ojeda // In cases when predicate and `drop` never panick, it will be optimized out. 1593753dece8SMiguel Ojeda struct BackshiftOnDrop<'a, T, A: Allocator> { 1594753dece8SMiguel Ojeda v: &'a mut Vec<T, A>, 1595753dece8SMiguel Ojeda processed_len: usize, 1596753dece8SMiguel Ojeda deleted_cnt: usize, 1597753dece8SMiguel Ojeda original_len: usize, 1598753dece8SMiguel Ojeda } 1599753dece8SMiguel Ojeda 1600753dece8SMiguel Ojeda impl<T, A: Allocator> Drop for BackshiftOnDrop<'_, T, A> { 1601753dece8SMiguel Ojeda fn drop(&mut self) { 1602753dece8SMiguel Ojeda if self.deleted_cnt > 0 { 1603753dece8SMiguel Ojeda // SAFETY: Trailing unchecked items must be valid since we never touch them. 1604753dece8SMiguel Ojeda unsafe { 1605753dece8SMiguel Ojeda ptr::copy( 1606753dece8SMiguel Ojeda self.v.as_ptr().add(self.processed_len), 1607753dece8SMiguel Ojeda self.v.as_mut_ptr().add(self.processed_len - self.deleted_cnt), 1608753dece8SMiguel Ojeda self.original_len - self.processed_len, 1609753dece8SMiguel Ojeda ); 1610753dece8SMiguel Ojeda } 1611753dece8SMiguel Ojeda } 1612753dece8SMiguel Ojeda // SAFETY: After filling holes, all items are in contiguous memory. 1613753dece8SMiguel Ojeda unsafe { 1614753dece8SMiguel Ojeda self.v.set_len(self.original_len - self.deleted_cnt); 1615753dece8SMiguel Ojeda } 1616753dece8SMiguel Ojeda } 1617753dece8SMiguel Ojeda } 1618753dece8SMiguel Ojeda 1619753dece8SMiguel Ojeda let mut g = BackshiftOnDrop { v: self, processed_len: 0, deleted_cnt: 0, original_len }; 1620753dece8SMiguel Ojeda 1621753dece8SMiguel Ojeda fn process_loop<F, T, A: Allocator, const DELETED: bool>( 1622753dece8SMiguel Ojeda original_len: usize, 1623753dece8SMiguel Ojeda f: &mut F, 1624753dece8SMiguel Ojeda g: &mut BackshiftOnDrop<'_, T, A>, 1625753dece8SMiguel Ojeda ) where 1626753dece8SMiguel Ojeda F: FnMut(&mut T) -> bool, 1627753dece8SMiguel Ojeda { 1628753dece8SMiguel Ojeda while g.processed_len != original_len { 1629753dece8SMiguel Ojeda // SAFETY: Unchecked element must be valid. 1630753dece8SMiguel Ojeda let cur = unsafe { &mut *g.v.as_mut_ptr().add(g.processed_len) }; 1631753dece8SMiguel Ojeda if !f(cur) { 1632753dece8SMiguel Ojeda // Advance early to avoid double drop if `drop_in_place` panicked. 1633753dece8SMiguel Ojeda g.processed_len += 1; 1634753dece8SMiguel Ojeda g.deleted_cnt += 1; 1635753dece8SMiguel Ojeda // SAFETY: We never touch this element again after dropped. 1636753dece8SMiguel Ojeda unsafe { ptr::drop_in_place(cur) }; 1637753dece8SMiguel Ojeda // We already advanced the counter. 1638753dece8SMiguel Ojeda if DELETED { 1639753dece8SMiguel Ojeda continue; 1640753dece8SMiguel Ojeda } else { 1641753dece8SMiguel Ojeda break; 1642753dece8SMiguel Ojeda } 1643753dece8SMiguel Ojeda } 1644753dece8SMiguel Ojeda if DELETED { 1645753dece8SMiguel Ojeda // SAFETY: `deleted_cnt` > 0, so the hole slot must not overlap with current element. 1646753dece8SMiguel Ojeda // We use copy for move, and never touch this element again. 1647753dece8SMiguel Ojeda unsafe { 1648753dece8SMiguel Ojeda let hole_slot = g.v.as_mut_ptr().add(g.processed_len - g.deleted_cnt); 1649753dece8SMiguel Ojeda ptr::copy_nonoverlapping(cur, hole_slot, 1); 1650753dece8SMiguel Ojeda } 1651753dece8SMiguel Ojeda } 1652753dece8SMiguel Ojeda g.processed_len += 1; 1653753dece8SMiguel Ojeda } 1654753dece8SMiguel Ojeda } 1655753dece8SMiguel Ojeda 1656753dece8SMiguel Ojeda // Stage 1: Nothing was deleted. 1657753dece8SMiguel Ojeda process_loop::<F, T, A, false>(original_len, &mut f, &mut g); 1658753dece8SMiguel Ojeda 1659753dece8SMiguel Ojeda // Stage 2: Some elements were deleted. 1660753dece8SMiguel Ojeda process_loop::<F, T, A, true>(original_len, &mut f, &mut g); 1661753dece8SMiguel Ojeda 1662753dece8SMiguel Ojeda // All item are processed. This can be optimized to `set_len` by LLVM. 1663753dece8SMiguel Ojeda drop(g); 1664753dece8SMiguel Ojeda } 1665753dece8SMiguel Ojeda 1666753dece8SMiguel Ojeda /// Removes all but the first of consecutive elements in the vector that resolve to the same 1667753dece8SMiguel Ojeda /// key. 1668753dece8SMiguel Ojeda /// 1669753dece8SMiguel Ojeda /// If the vector is sorted, this removes all duplicates. 1670753dece8SMiguel Ojeda /// 1671753dece8SMiguel Ojeda /// # Examples 1672753dece8SMiguel Ojeda /// 1673753dece8SMiguel Ojeda /// ``` 1674753dece8SMiguel Ojeda /// let mut vec = vec![10, 20, 21, 30, 20]; 1675753dece8SMiguel Ojeda /// 1676753dece8SMiguel Ojeda /// vec.dedup_by_key(|i| *i / 10); 1677753dece8SMiguel Ojeda /// 1678753dece8SMiguel Ojeda /// assert_eq!(vec, [10, 20, 30, 20]); 1679753dece8SMiguel Ojeda /// ``` 1680753dece8SMiguel Ojeda #[stable(feature = "dedup_by", since = "1.16.0")] 1681753dece8SMiguel Ojeda #[inline] 1682753dece8SMiguel Ojeda pub fn dedup_by_key<F, K>(&mut self, mut key: F) 1683753dece8SMiguel Ojeda where 1684753dece8SMiguel Ojeda F: FnMut(&mut T) -> K, 1685753dece8SMiguel Ojeda K: PartialEq, 1686753dece8SMiguel Ojeda { 1687753dece8SMiguel Ojeda self.dedup_by(|a, b| key(a) == key(b)) 1688753dece8SMiguel Ojeda } 1689753dece8SMiguel Ojeda 1690753dece8SMiguel Ojeda /// Removes all but the first of consecutive elements in the vector satisfying a given equality 1691753dece8SMiguel Ojeda /// relation. 1692753dece8SMiguel Ojeda /// 1693753dece8SMiguel Ojeda /// The `same_bucket` function is passed references to two elements from the vector and 1694753dece8SMiguel Ojeda /// must determine if the elements compare equal. The elements are passed in opposite order 1695753dece8SMiguel Ojeda /// from their order in the slice, so if `same_bucket(a, b)` returns `true`, `a` is removed. 1696753dece8SMiguel Ojeda /// 1697753dece8SMiguel Ojeda /// If the vector is sorted, this removes all duplicates. 1698753dece8SMiguel Ojeda /// 1699753dece8SMiguel Ojeda /// # Examples 1700753dece8SMiguel Ojeda /// 1701753dece8SMiguel Ojeda /// ``` 1702753dece8SMiguel Ojeda /// let mut vec = vec!["foo", "bar", "Bar", "baz", "bar"]; 1703753dece8SMiguel Ojeda /// 1704753dece8SMiguel Ojeda /// vec.dedup_by(|a, b| a.eq_ignore_ascii_case(b)); 1705753dece8SMiguel Ojeda /// 1706753dece8SMiguel Ojeda /// assert_eq!(vec, ["foo", "bar", "baz", "bar"]); 1707753dece8SMiguel Ojeda /// ``` 1708753dece8SMiguel Ojeda #[stable(feature = "dedup_by", since = "1.16.0")] 1709753dece8SMiguel Ojeda pub fn dedup_by<F>(&mut self, mut same_bucket: F) 1710753dece8SMiguel Ojeda where 1711753dece8SMiguel Ojeda F: FnMut(&mut T, &mut T) -> bool, 1712753dece8SMiguel Ojeda { 1713753dece8SMiguel Ojeda let len = self.len(); 1714753dece8SMiguel Ojeda if len <= 1 { 1715753dece8SMiguel Ojeda return; 1716753dece8SMiguel Ojeda } 1717753dece8SMiguel Ojeda 1718753dece8SMiguel Ojeda /* INVARIANT: vec.len() > read >= write > write-1 >= 0 */ 1719753dece8SMiguel Ojeda struct FillGapOnDrop<'a, T, A: core::alloc::Allocator> { 1720753dece8SMiguel Ojeda /* Offset of the element we want to check if it is duplicate */ 1721753dece8SMiguel Ojeda read: usize, 1722753dece8SMiguel Ojeda 1723753dece8SMiguel Ojeda /* Offset of the place where we want to place the non-duplicate 1724753dece8SMiguel Ojeda * when we find it. */ 1725753dece8SMiguel Ojeda write: usize, 1726753dece8SMiguel Ojeda 1727753dece8SMiguel Ojeda /* The Vec that would need correction if `same_bucket` panicked */ 1728753dece8SMiguel Ojeda vec: &'a mut Vec<T, A>, 1729753dece8SMiguel Ojeda } 1730753dece8SMiguel Ojeda 1731753dece8SMiguel Ojeda impl<'a, T, A: core::alloc::Allocator> Drop for FillGapOnDrop<'a, T, A> { 1732753dece8SMiguel Ojeda fn drop(&mut self) { 1733753dece8SMiguel Ojeda /* This code gets executed when `same_bucket` panics */ 1734753dece8SMiguel Ojeda 1735753dece8SMiguel Ojeda /* SAFETY: invariant guarantees that `read - write` 1736753dece8SMiguel Ojeda * and `len - read` never overflow and that the copy is always 1737753dece8SMiguel Ojeda * in-bounds. */ 1738753dece8SMiguel Ojeda unsafe { 1739753dece8SMiguel Ojeda let ptr = self.vec.as_mut_ptr(); 1740753dece8SMiguel Ojeda let len = self.vec.len(); 1741753dece8SMiguel Ojeda 1742753dece8SMiguel Ojeda /* How many items were left when `same_bucket` panicked. 1743753dece8SMiguel Ojeda * Basically vec[read..].len() */ 1744753dece8SMiguel Ojeda let items_left = len.wrapping_sub(self.read); 1745753dece8SMiguel Ojeda 1746753dece8SMiguel Ojeda /* Pointer to first item in vec[write..write+items_left] slice */ 1747753dece8SMiguel Ojeda let dropped_ptr = ptr.add(self.write); 1748753dece8SMiguel Ojeda /* Pointer to first item in vec[read..] slice */ 1749753dece8SMiguel Ojeda let valid_ptr = ptr.add(self.read); 1750753dece8SMiguel Ojeda 1751753dece8SMiguel Ojeda /* Copy `vec[read..]` to `vec[write..write+items_left]`. 1752753dece8SMiguel Ojeda * The slices can overlap, so `copy_nonoverlapping` cannot be used */ 1753753dece8SMiguel Ojeda ptr::copy(valid_ptr, dropped_ptr, items_left); 1754753dece8SMiguel Ojeda 1755753dece8SMiguel Ojeda /* How many items have been already dropped 1756753dece8SMiguel Ojeda * Basically vec[read..write].len() */ 1757753dece8SMiguel Ojeda let dropped = self.read.wrapping_sub(self.write); 1758753dece8SMiguel Ojeda 1759753dece8SMiguel Ojeda self.vec.set_len(len - dropped); 1760753dece8SMiguel Ojeda } 1761753dece8SMiguel Ojeda } 1762753dece8SMiguel Ojeda } 1763753dece8SMiguel Ojeda 1764753dece8SMiguel Ojeda let mut gap = FillGapOnDrop { read: 1, write: 1, vec: self }; 1765753dece8SMiguel Ojeda let ptr = gap.vec.as_mut_ptr(); 1766753dece8SMiguel Ojeda 1767753dece8SMiguel Ojeda /* Drop items while going through Vec, it should be more efficient than 1768753dece8SMiguel Ojeda * doing slice partition_dedup + truncate */ 1769753dece8SMiguel Ojeda 1770753dece8SMiguel Ojeda /* SAFETY: Because of the invariant, read_ptr, prev_ptr and write_ptr 1771753dece8SMiguel Ojeda * are always in-bounds and read_ptr never aliases prev_ptr */ 1772753dece8SMiguel Ojeda unsafe { 1773753dece8SMiguel Ojeda while gap.read < len { 1774753dece8SMiguel Ojeda let read_ptr = ptr.add(gap.read); 1775753dece8SMiguel Ojeda let prev_ptr = ptr.add(gap.write.wrapping_sub(1)); 1776753dece8SMiguel Ojeda 1777753dece8SMiguel Ojeda if same_bucket(&mut *read_ptr, &mut *prev_ptr) { 1778753dece8SMiguel Ojeda // Increase `gap.read` now since the drop may panic. 1779753dece8SMiguel Ojeda gap.read += 1; 1780753dece8SMiguel Ojeda /* We have found duplicate, drop it in-place */ 1781753dece8SMiguel Ojeda ptr::drop_in_place(read_ptr); 1782753dece8SMiguel Ojeda } else { 1783753dece8SMiguel Ojeda let write_ptr = ptr.add(gap.write); 1784753dece8SMiguel Ojeda 1785753dece8SMiguel Ojeda /* Because `read_ptr` can be equal to `write_ptr`, we either 1786753dece8SMiguel Ojeda * have to use `copy` or conditional `copy_nonoverlapping`. 1787753dece8SMiguel Ojeda * Looks like the first option is faster. */ 1788753dece8SMiguel Ojeda ptr::copy(read_ptr, write_ptr, 1); 1789753dece8SMiguel Ojeda 1790753dece8SMiguel Ojeda /* We have filled that place, so go further */ 1791753dece8SMiguel Ojeda gap.write += 1; 1792753dece8SMiguel Ojeda gap.read += 1; 1793753dece8SMiguel Ojeda } 1794753dece8SMiguel Ojeda } 1795753dece8SMiguel Ojeda 1796753dece8SMiguel Ojeda /* Technically we could let `gap` clean up with its Drop, but 1797753dece8SMiguel Ojeda * when `same_bucket` is guaranteed to not panic, this bloats a little 1798753dece8SMiguel Ojeda * the codegen, so we just do it manually */ 1799753dece8SMiguel Ojeda gap.vec.set_len(gap.write); 1800753dece8SMiguel Ojeda mem::forget(gap); 1801753dece8SMiguel Ojeda } 1802753dece8SMiguel Ojeda } 1803753dece8SMiguel Ojeda 1804753dece8SMiguel Ojeda /// Appends an element to the back of a collection. 1805753dece8SMiguel Ojeda /// 1806753dece8SMiguel Ojeda /// # Panics 1807753dece8SMiguel Ojeda /// 1808753dece8SMiguel Ojeda /// Panics if the new capacity exceeds `isize::MAX` bytes. 1809753dece8SMiguel Ojeda /// 1810753dece8SMiguel Ojeda /// # Examples 1811753dece8SMiguel Ojeda /// 1812753dece8SMiguel Ojeda /// ``` 1813753dece8SMiguel Ojeda /// let mut vec = vec![1, 2]; 1814753dece8SMiguel Ojeda /// vec.push(3); 1815753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2, 3]); 1816753dece8SMiguel Ojeda /// ``` 1817753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 1818753dece8SMiguel Ojeda #[inline] 1819753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1820753dece8SMiguel Ojeda pub fn push(&mut self, value: T) { 1821753dece8SMiguel Ojeda // This will panic or abort if we would allocate > isize::MAX bytes 1822753dece8SMiguel Ojeda // or if the length increment would overflow for zero-sized types. 1823753dece8SMiguel Ojeda if self.len == self.buf.capacity() { 1824753dece8SMiguel Ojeda self.buf.reserve_for_push(self.len); 1825753dece8SMiguel Ojeda } 1826753dece8SMiguel Ojeda unsafe { 1827753dece8SMiguel Ojeda let end = self.as_mut_ptr().add(self.len); 1828753dece8SMiguel Ojeda ptr::write(end, value); 1829753dece8SMiguel Ojeda self.len += 1; 1830753dece8SMiguel Ojeda } 1831753dece8SMiguel Ojeda } 1832753dece8SMiguel Ojeda 1833057b8d25SMiguel Ojeda /// Tries to append an element to the back of a collection. 1834057b8d25SMiguel Ojeda /// 1835057b8d25SMiguel Ojeda /// # Examples 1836057b8d25SMiguel Ojeda /// 1837057b8d25SMiguel Ojeda /// ``` 1838057b8d25SMiguel Ojeda /// let mut vec = vec![1, 2]; 1839057b8d25SMiguel Ojeda /// vec.try_push(3).unwrap(); 1840057b8d25SMiguel Ojeda /// assert_eq!(vec, [1, 2, 3]); 1841057b8d25SMiguel Ojeda /// ``` 1842057b8d25SMiguel Ojeda #[inline] 1843057b8d25SMiguel Ojeda #[stable(feature = "kernel", since = "1.0.0")] 1844057b8d25SMiguel Ojeda pub fn try_push(&mut self, value: T) -> Result<(), TryReserveError> { 1845057b8d25SMiguel Ojeda if self.len == self.buf.capacity() { 1846057b8d25SMiguel Ojeda self.buf.try_reserve_for_push(self.len)?; 1847057b8d25SMiguel Ojeda } 1848057b8d25SMiguel Ojeda unsafe { 1849057b8d25SMiguel Ojeda let end = self.as_mut_ptr().add(self.len); 1850057b8d25SMiguel Ojeda ptr::write(end, value); 1851057b8d25SMiguel Ojeda self.len += 1; 1852057b8d25SMiguel Ojeda } 1853057b8d25SMiguel Ojeda Ok(()) 1854057b8d25SMiguel Ojeda } 1855057b8d25SMiguel Ojeda 1856753dece8SMiguel Ojeda /// Removes the last element from a vector and returns it, or [`None`] if it 1857753dece8SMiguel Ojeda /// is empty. 1858753dece8SMiguel Ojeda /// 1859753dece8SMiguel Ojeda /// If you'd like to pop the first element, consider using 1860753dece8SMiguel Ojeda /// [`VecDeque::pop_front`] instead. 1861753dece8SMiguel Ojeda /// 1862753dece8SMiguel Ojeda /// [`VecDeque::pop_front`]: crate::collections::VecDeque::pop_front 1863753dece8SMiguel Ojeda /// 1864753dece8SMiguel Ojeda /// # Examples 1865753dece8SMiguel Ojeda /// 1866753dece8SMiguel Ojeda /// ``` 1867753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3]; 1868753dece8SMiguel Ojeda /// assert_eq!(vec.pop(), Some(3)); 1869753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2]); 1870753dece8SMiguel Ojeda /// ``` 1871753dece8SMiguel Ojeda #[inline] 1872753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1873753dece8SMiguel Ojeda pub fn pop(&mut self) -> Option<T> { 1874753dece8SMiguel Ojeda if self.len == 0 { 1875753dece8SMiguel Ojeda None 1876753dece8SMiguel Ojeda } else { 1877753dece8SMiguel Ojeda unsafe { 1878753dece8SMiguel Ojeda self.len -= 1; 1879753dece8SMiguel Ojeda Some(ptr::read(self.as_ptr().add(self.len()))) 1880753dece8SMiguel Ojeda } 1881753dece8SMiguel Ojeda } 1882753dece8SMiguel Ojeda } 1883753dece8SMiguel Ojeda 1884753dece8SMiguel Ojeda /// Moves all the elements of `other` into `self`, leaving `other` empty. 1885753dece8SMiguel Ojeda /// 1886753dece8SMiguel Ojeda /// # Panics 1887753dece8SMiguel Ojeda /// 1888753dece8SMiguel Ojeda /// Panics if the number of elements in the vector overflows a `usize`. 1889753dece8SMiguel Ojeda /// 1890753dece8SMiguel Ojeda /// # Examples 1891753dece8SMiguel Ojeda /// 1892753dece8SMiguel Ojeda /// ``` 1893753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3]; 1894753dece8SMiguel Ojeda /// let mut vec2 = vec![4, 5, 6]; 1895753dece8SMiguel Ojeda /// vec.append(&mut vec2); 1896753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2, 3, 4, 5, 6]); 1897753dece8SMiguel Ojeda /// assert_eq!(vec2, []); 1898753dece8SMiguel Ojeda /// ``` 1899753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 1900753dece8SMiguel Ojeda #[inline] 1901753dece8SMiguel Ojeda #[stable(feature = "append", since = "1.4.0")] 1902753dece8SMiguel Ojeda pub fn append(&mut self, other: &mut Self) { 1903753dece8SMiguel Ojeda unsafe { 1904753dece8SMiguel Ojeda self.append_elements(other.as_slice() as _); 1905753dece8SMiguel Ojeda other.set_len(0); 1906753dece8SMiguel Ojeda } 1907753dece8SMiguel Ojeda } 1908753dece8SMiguel Ojeda 1909753dece8SMiguel Ojeda /// Appends elements to `self` from other buffer. 1910753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 1911753dece8SMiguel Ojeda #[inline] 1912753dece8SMiguel Ojeda unsafe fn append_elements(&mut self, other: *const [T]) { 1913753dece8SMiguel Ojeda let count = unsafe { (*other).len() }; 1914753dece8SMiguel Ojeda self.reserve(count); 1915753dece8SMiguel Ojeda let len = self.len(); 1916753dece8SMiguel Ojeda unsafe { ptr::copy_nonoverlapping(other as *const T, self.as_mut_ptr().add(len), count) }; 1917753dece8SMiguel Ojeda self.len += count; 1918753dece8SMiguel Ojeda } 1919753dece8SMiguel Ojeda 1920753dece8SMiguel Ojeda /// Removes the specified range from the vector in bulk, returning all 1921753dece8SMiguel Ojeda /// removed elements as an iterator. If the iterator is dropped before 1922753dece8SMiguel Ojeda /// being fully consumed, it drops the remaining removed elements. 1923753dece8SMiguel Ojeda /// 1924753dece8SMiguel Ojeda /// The returned iterator keeps a mutable borrow on the vector to optimize 1925753dece8SMiguel Ojeda /// its implementation. 1926753dece8SMiguel Ojeda /// 1927753dece8SMiguel Ojeda /// # Panics 1928753dece8SMiguel Ojeda /// 1929753dece8SMiguel Ojeda /// Panics if the starting point is greater than the end point or if 1930753dece8SMiguel Ojeda /// the end point is greater than the length of the vector. 1931753dece8SMiguel Ojeda /// 1932753dece8SMiguel Ojeda /// # Leaking 1933753dece8SMiguel Ojeda /// 1934753dece8SMiguel Ojeda /// If the returned iterator goes out of scope without being dropped (due to 1935753dece8SMiguel Ojeda /// [`mem::forget`], for example), the vector may have lost and leaked 1936753dece8SMiguel Ojeda /// elements arbitrarily, including elements outside the range. 1937753dece8SMiguel Ojeda /// 1938753dece8SMiguel Ojeda /// # Examples 1939753dece8SMiguel Ojeda /// 1940753dece8SMiguel Ojeda /// ``` 1941753dece8SMiguel Ojeda /// let mut v = vec![1, 2, 3]; 1942753dece8SMiguel Ojeda /// let u: Vec<_> = v.drain(1..).collect(); 1943753dece8SMiguel Ojeda /// assert_eq!(v, &[1]); 1944753dece8SMiguel Ojeda /// assert_eq!(u, &[2, 3]); 1945753dece8SMiguel Ojeda /// 1946753dece8SMiguel Ojeda /// // A full range clears the vector, like `clear()` does 1947753dece8SMiguel Ojeda /// v.drain(..); 1948753dece8SMiguel Ojeda /// assert_eq!(v, &[]); 1949753dece8SMiguel Ojeda /// ``` 1950753dece8SMiguel Ojeda #[stable(feature = "drain", since = "1.6.0")] 1951753dece8SMiguel Ojeda pub fn drain<R>(&mut self, range: R) -> Drain<'_, T, A> 1952753dece8SMiguel Ojeda where 1953753dece8SMiguel Ojeda R: RangeBounds<usize>, 1954753dece8SMiguel Ojeda { 1955753dece8SMiguel Ojeda // Memory safety 1956753dece8SMiguel Ojeda // 1957753dece8SMiguel Ojeda // When the Drain is first created, it shortens the length of 1958753dece8SMiguel Ojeda // the source vector to make sure no uninitialized or moved-from elements 1959753dece8SMiguel Ojeda // are accessible at all if the Drain's destructor never gets to run. 1960753dece8SMiguel Ojeda // 1961753dece8SMiguel Ojeda // Drain will ptr::read out the values to remove. 1962753dece8SMiguel Ojeda // When finished, remaining tail of the vec is copied back to cover 1963753dece8SMiguel Ojeda // the hole, and the vector length is restored to the new length. 1964753dece8SMiguel Ojeda // 1965753dece8SMiguel Ojeda let len = self.len(); 1966753dece8SMiguel Ojeda let Range { start, end } = slice::range(range, ..len); 1967753dece8SMiguel Ojeda 1968753dece8SMiguel Ojeda unsafe { 1969753dece8SMiguel Ojeda // set self.vec length's to start, to be safe in case Drain is leaked 1970753dece8SMiguel Ojeda self.set_len(start); 1971753dece8SMiguel Ojeda // Use the borrow in the IterMut to indicate borrowing behavior of the 1972753dece8SMiguel Ojeda // whole Drain iterator (like &mut T). 1973753dece8SMiguel Ojeda let range_slice = slice::from_raw_parts_mut(self.as_mut_ptr().add(start), end - start); 1974753dece8SMiguel Ojeda Drain { 1975753dece8SMiguel Ojeda tail_start: end, 1976753dece8SMiguel Ojeda tail_len: len - end, 1977753dece8SMiguel Ojeda iter: range_slice.iter(), 1978753dece8SMiguel Ojeda vec: NonNull::from(self), 1979753dece8SMiguel Ojeda } 1980753dece8SMiguel Ojeda } 1981753dece8SMiguel Ojeda } 1982753dece8SMiguel Ojeda 1983753dece8SMiguel Ojeda /// Clears the vector, removing all values. 1984753dece8SMiguel Ojeda /// 1985753dece8SMiguel Ojeda /// Note that this method has no effect on the allocated capacity 1986753dece8SMiguel Ojeda /// of the vector. 1987753dece8SMiguel Ojeda /// 1988753dece8SMiguel Ojeda /// # Examples 1989753dece8SMiguel Ojeda /// 1990753dece8SMiguel Ojeda /// ``` 1991753dece8SMiguel Ojeda /// let mut v = vec![1, 2, 3]; 1992753dece8SMiguel Ojeda /// 1993753dece8SMiguel Ojeda /// v.clear(); 1994753dece8SMiguel Ojeda /// 1995753dece8SMiguel Ojeda /// assert!(v.is_empty()); 1996753dece8SMiguel Ojeda /// ``` 1997753dece8SMiguel Ojeda #[inline] 1998753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1999753dece8SMiguel Ojeda pub fn clear(&mut self) { 2000753dece8SMiguel Ojeda let elems: *mut [T] = self.as_mut_slice(); 2001753dece8SMiguel Ojeda 2002753dece8SMiguel Ojeda // SAFETY: 2003753dece8SMiguel Ojeda // - `elems` comes directly from `as_mut_slice` and is therefore valid. 2004753dece8SMiguel Ojeda // - Setting `self.len` before calling `drop_in_place` means that, 2005753dece8SMiguel Ojeda // if an element's `Drop` impl panics, the vector's `Drop` impl will 2006753dece8SMiguel Ojeda // do nothing (leaking the rest of the elements) instead of dropping 2007753dece8SMiguel Ojeda // some twice. 2008753dece8SMiguel Ojeda unsafe { 2009753dece8SMiguel Ojeda self.len = 0; 2010753dece8SMiguel Ojeda ptr::drop_in_place(elems); 2011753dece8SMiguel Ojeda } 2012753dece8SMiguel Ojeda } 2013753dece8SMiguel Ojeda 2014753dece8SMiguel Ojeda /// Returns the number of elements in the vector, also referred to 2015753dece8SMiguel Ojeda /// as its 'length'. 2016753dece8SMiguel Ojeda /// 2017753dece8SMiguel Ojeda /// # Examples 2018753dece8SMiguel Ojeda /// 2019753dece8SMiguel Ojeda /// ``` 2020753dece8SMiguel Ojeda /// let a = vec![1, 2, 3]; 2021753dece8SMiguel Ojeda /// assert_eq!(a.len(), 3); 2022753dece8SMiguel Ojeda /// ``` 2023753dece8SMiguel Ojeda #[inline] 2024753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2025753dece8SMiguel Ojeda pub fn len(&self) -> usize { 2026753dece8SMiguel Ojeda self.len 2027753dece8SMiguel Ojeda } 2028753dece8SMiguel Ojeda 2029753dece8SMiguel Ojeda /// Returns `true` if the vector contains no elements. 2030753dece8SMiguel Ojeda /// 2031753dece8SMiguel Ojeda /// # Examples 2032753dece8SMiguel Ojeda /// 2033753dece8SMiguel Ojeda /// ``` 2034753dece8SMiguel Ojeda /// let mut v = Vec::new(); 2035753dece8SMiguel Ojeda /// assert!(v.is_empty()); 2036753dece8SMiguel Ojeda /// 2037753dece8SMiguel Ojeda /// v.push(1); 2038753dece8SMiguel Ojeda /// assert!(!v.is_empty()); 2039753dece8SMiguel Ojeda /// ``` 2040753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2041753dece8SMiguel Ojeda pub fn is_empty(&self) -> bool { 2042753dece8SMiguel Ojeda self.len() == 0 2043753dece8SMiguel Ojeda } 2044753dece8SMiguel Ojeda 2045753dece8SMiguel Ojeda /// Splits the collection into two at the given index. 2046753dece8SMiguel Ojeda /// 2047753dece8SMiguel Ojeda /// Returns a newly allocated vector containing the elements in the range 2048753dece8SMiguel Ojeda /// `[at, len)`. After the call, the original vector will be left containing 2049753dece8SMiguel Ojeda /// the elements `[0, at)` with its previous capacity unchanged. 2050753dece8SMiguel Ojeda /// 2051753dece8SMiguel Ojeda /// # Panics 2052753dece8SMiguel Ojeda /// 2053753dece8SMiguel Ojeda /// Panics if `at > len`. 2054753dece8SMiguel Ojeda /// 2055753dece8SMiguel Ojeda /// # Examples 2056753dece8SMiguel Ojeda /// 2057753dece8SMiguel Ojeda /// ``` 2058753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3]; 2059753dece8SMiguel Ojeda /// let vec2 = vec.split_off(1); 2060753dece8SMiguel Ojeda /// assert_eq!(vec, [1]); 2061753dece8SMiguel Ojeda /// assert_eq!(vec2, [2, 3]); 2062753dece8SMiguel Ojeda /// ``` 2063753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2064753dece8SMiguel Ojeda #[inline] 2065753dece8SMiguel Ojeda #[must_use = "use `.truncate()` if you don't need the other half"] 2066753dece8SMiguel Ojeda #[stable(feature = "split_off", since = "1.4.0")] 2067753dece8SMiguel Ojeda pub fn split_off(&mut self, at: usize) -> Self 2068753dece8SMiguel Ojeda where 2069753dece8SMiguel Ojeda A: Clone, 2070753dece8SMiguel Ojeda { 2071753dece8SMiguel Ojeda #[cold] 2072753dece8SMiguel Ojeda #[inline(never)] 2073753dece8SMiguel Ojeda fn assert_failed(at: usize, len: usize) -> ! { 2074753dece8SMiguel Ojeda panic!("`at` split index (is {at}) should be <= len (is {len})"); 2075753dece8SMiguel Ojeda } 2076753dece8SMiguel Ojeda 2077753dece8SMiguel Ojeda if at > self.len() { 2078753dece8SMiguel Ojeda assert_failed(at, self.len()); 2079753dece8SMiguel Ojeda } 2080753dece8SMiguel Ojeda 2081753dece8SMiguel Ojeda if at == 0 { 2082753dece8SMiguel Ojeda // the new vector can take over the original buffer and avoid the copy 2083753dece8SMiguel Ojeda return mem::replace( 2084753dece8SMiguel Ojeda self, 2085753dece8SMiguel Ojeda Vec::with_capacity_in(self.capacity(), self.allocator().clone()), 2086753dece8SMiguel Ojeda ); 2087753dece8SMiguel Ojeda } 2088753dece8SMiguel Ojeda 2089753dece8SMiguel Ojeda let other_len = self.len - at; 2090753dece8SMiguel Ojeda let mut other = Vec::with_capacity_in(other_len, self.allocator().clone()); 2091753dece8SMiguel Ojeda 2092753dece8SMiguel Ojeda // Unsafely `set_len` and copy items to `other`. 2093753dece8SMiguel Ojeda unsafe { 2094753dece8SMiguel Ojeda self.set_len(at); 2095753dece8SMiguel Ojeda other.set_len(other_len); 2096753dece8SMiguel Ojeda 2097753dece8SMiguel Ojeda ptr::copy_nonoverlapping(self.as_ptr().add(at), other.as_mut_ptr(), other.len()); 2098753dece8SMiguel Ojeda } 2099753dece8SMiguel Ojeda other 2100753dece8SMiguel Ojeda } 2101753dece8SMiguel Ojeda 2102753dece8SMiguel Ojeda /// Resizes the `Vec` in-place so that `len` is equal to `new_len`. 2103753dece8SMiguel Ojeda /// 2104753dece8SMiguel Ojeda /// If `new_len` is greater than `len`, the `Vec` is extended by the 2105753dece8SMiguel Ojeda /// difference, with each additional slot filled with the result of 2106753dece8SMiguel Ojeda /// calling the closure `f`. The return values from `f` will end up 2107753dece8SMiguel Ojeda /// in the `Vec` in the order they have been generated. 2108753dece8SMiguel Ojeda /// 2109753dece8SMiguel Ojeda /// If `new_len` is less than `len`, the `Vec` is simply truncated. 2110753dece8SMiguel Ojeda /// 2111753dece8SMiguel Ojeda /// This method uses a closure to create new values on every push. If 2112753dece8SMiguel Ojeda /// you'd rather [`Clone`] a given value, use [`Vec::resize`]. If you 2113753dece8SMiguel Ojeda /// want to use the [`Default`] trait to generate values, you can 2114753dece8SMiguel Ojeda /// pass [`Default::default`] as the second argument. 2115753dece8SMiguel Ojeda /// 2116753dece8SMiguel Ojeda /// # Examples 2117753dece8SMiguel Ojeda /// 2118753dece8SMiguel Ojeda /// ``` 2119753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3]; 2120753dece8SMiguel Ojeda /// vec.resize_with(5, Default::default); 2121753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2, 3, 0, 0]); 2122753dece8SMiguel Ojeda /// 2123753dece8SMiguel Ojeda /// let mut vec = vec![]; 2124753dece8SMiguel Ojeda /// let mut p = 1; 2125753dece8SMiguel Ojeda /// vec.resize_with(4, || { p *= 2; p }); 2126753dece8SMiguel Ojeda /// assert_eq!(vec, [2, 4, 8, 16]); 2127753dece8SMiguel Ojeda /// ``` 2128753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2129753dece8SMiguel Ojeda #[stable(feature = "vec_resize_with", since = "1.33.0")] 2130753dece8SMiguel Ojeda pub fn resize_with<F>(&mut self, new_len: usize, f: F) 2131753dece8SMiguel Ojeda where 2132753dece8SMiguel Ojeda F: FnMut() -> T, 2133753dece8SMiguel Ojeda { 2134753dece8SMiguel Ojeda let len = self.len(); 2135753dece8SMiguel Ojeda if new_len > len { 2136753dece8SMiguel Ojeda self.extend_with(new_len - len, ExtendFunc(f)); 2137753dece8SMiguel Ojeda } else { 2138753dece8SMiguel Ojeda self.truncate(new_len); 2139753dece8SMiguel Ojeda } 2140753dece8SMiguel Ojeda } 2141753dece8SMiguel Ojeda 2142753dece8SMiguel Ojeda /// Consumes and leaks the `Vec`, returning a mutable reference to the contents, 2143753dece8SMiguel Ojeda /// `&'a mut [T]`. Note that the type `T` must outlive the chosen lifetime 2144753dece8SMiguel Ojeda /// `'a`. If the type has only static references, or none at all, then this 2145753dece8SMiguel Ojeda /// may be chosen to be `'static`. 2146753dece8SMiguel Ojeda /// 2147753dece8SMiguel Ojeda /// As of Rust 1.57, this method does not reallocate or shrink the `Vec`, 2148753dece8SMiguel Ojeda /// so the leaked allocation may include unused capacity that is not part 2149753dece8SMiguel Ojeda /// of the returned slice. 2150753dece8SMiguel Ojeda /// 2151753dece8SMiguel Ojeda /// This function is mainly useful for data that lives for the remainder of 2152753dece8SMiguel Ojeda /// the program's life. Dropping the returned reference will cause a memory 2153753dece8SMiguel Ojeda /// leak. 2154753dece8SMiguel Ojeda /// 2155753dece8SMiguel Ojeda /// # Examples 2156753dece8SMiguel Ojeda /// 2157753dece8SMiguel Ojeda /// Simple usage: 2158753dece8SMiguel Ojeda /// 2159753dece8SMiguel Ojeda /// ``` 2160753dece8SMiguel Ojeda /// let x = vec![1, 2, 3]; 2161753dece8SMiguel Ojeda /// let static_ref: &'static mut [usize] = x.leak(); 2162753dece8SMiguel Ojeda /// static_ref[0] += 1; 2163753dece8SMiguel Ojeda /// assert_eq!(static_ref, &[2, 2, 3]); 2164753dece8SMiguel Ojeda /// ``` 2165753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2166753dece8SMiguel Ojeda #[stable(feature = "vec_leak", since = "1.47.0")] 2167753dece8SMiguel Ojeda #[inline] 2168753dece8SMiguel Ojeda pub fn leak<'a>(self) -> &'a mut [T] 2169753dece8SMiguel Ojeda where 2170753dece8SMiguel Ojeda A: 'a, 2171753dece8SMiguel Ojeda { 2172753dece8SMiguel Ojeda let mut me = ManuallyDrop::new(self); 2173753dece8SMiguel Ojeda unsafe { slice::from_raw_parts_mut(me.as_mut_ptr(), me.len) } 2174753dece8SMiguel Ojeda } 2175753dece8SMiguel Ojeda 2176753dece8SMiguel Ojeda /// Returns the remaining spare capacity of the vector as a slice of 2177753dece8SMiguel Ojeda /// `MaybeUninit<T>`. 2178753dece8SMiguel Ojeda /// 2179753dece8SMiguel Ojeda /// The returned slice can be used to fill the vector with data (e.g. by 2180753dece8SMiguel Ojeda /// reading from a file) before marking the data as initialized using the 2181753dece8SMiguel Ojeda /// [`set_len`] method. 2182753dece8SMiguel Ojeda /// 2183753dece8SMiguel Ojeda /// [`set_len`]: Vec::set_len 2184753dece8SMiguel Ojeda /// 2185753dece8SMiguel Ojeda /// # Examples 2186753dece8SMiguel Ojeda /// 2187753dece8SMiguel Ojeda /// ``` 2188753dece8SMiguel Ojeda /// // Allocate vector big enough for 10 elements. 2189753dece8SMiguel Ojeda /// let mut v = Vec::with_capacity(10); 2190753dece8SMiguel Ojeda /// 2191753dece8SMiguel Ojeda /// // Fill in the first 3 elements. 2192753dece8SMiguel Ojeda /// let uninit = v.spare_capacity_mut(); 2193753dece8SMiguel Ojeda /// uninit[0].write(0); 2194753dece8SMiguel Ojeda /// uninit[1].write(1); 2195753dece8SMiguel Ojeda /// uninit[2].write(2); 2196753dece8SMiguel Ojeda /// 2197753dece8SMiguel Ojeda /// // Mark the first 3 elements of the vector as being initialized. 2198753dece8SMiguel Ojeda /// unsafe { 2199753dece8SMiguel Ojeda /// v.set_len(3); 2200753dece8SMiguel Ojeda /// } 2201753dece8SMiguel Ojeda /// 2202753dece8SMiguel Ojeda /// assert_eq!(&v, &[0, 1, 2]); 2203753dece8SMiguel Ojeda /// ``` 2204753dece8SMiguel Ojeda #[stable(feature = "vec_spare_capacity", since = "1.60.0")] 2205753dece8SMiguel Ojeda #[inline] 2206753dece8SMiguel Ojeda pub fn spare_capacity_mut(&mut self) -> &mut [MaybeUninit<T>] { 2207753dece8SMiguel Ojeda // Note: 2208753dece8SMiguel Ojeda // This method is not implemented in terms of `split_at_spare_mut`, 2209753dece8SMiguel Ojeda // to prevent invalidation of pointers to the buffer. 2210753dece8SMiguel Ojeda unsafe { 2211753dece8SMiguel Ojeda slice::from_raw_parts_mut( 2212753dece8SMiguel Ojeda self.as_mut_ptr().add(self.len) as *mut MaybeUninit<T>, 2213753dece8SMiguel Ojeda self.buf.capacity() - self.len, 2214753dece8SMiguel Ojeda ) 2215753dece8SMiguel Ojeda } 2216753dece8SMiguel Ojeda } 2217753dece8SMiguel Ojeda 2218753dece8SMiguel Ojeda /// Returns vector content as a slice of `T`, along with the remaining spare 2219753dece8SMiguel Ojeda /// capacity of the vector as a slice of `MaybeUninit<T>`. 2220753dece8SMiguel Ojeda /// 2221753dece8SMiguel Ojeda /// The returned spare capacity slice can be used to fill the vector with data 2222753dece8SMiguel Ojeda /// (e.g. by reading from a file) before marking the data as initialized using 2223753dece8SMiguel Ojeda /// the [`set_len`] method. 2224753dece8SMiguel Ojeda /// 2225753dece8SMiguel Ojeda /// [`set_len`]: Vec::set_len 2226753dece8SMiguel Ojeda /// 2227753dece8SMiguel Ojeda /// Note that this is a low-level API, which should be used with care for 2228753dece8SMiguel Ojeda /// optimization purposes. If you need to append data to a `Vec` 2229753dece8SMiguel Ojeda /// you can use [`push`], [`extend`], [`extend_from_slice`], 2230753dece8SMiguel Ojeda /// [`extend_from_within`], [`insert`], [`append`], [`resize`] or 2231753dece8SMiguel Ojeda /// [`resize_with`], depending on your exact needs. 2232753dece8SMiguel Ojeda /// 2233753dece8SMiguel Ojeda /// [`push`]: Vec::push 2234753dece8SMiguel Ojeda /// [`extend`]: Vec::extend 2235753dece8SMiguel Ojeda /// [`extend_from_slice`]: Vec::extend_from_slice 2236753dece8SMiguel Ojeda /// [`extend_from_within`]: Vec::extend_from_within 2237753dece8SMiguel Ojeda /// [`insert`]: Vec::insert 2238753dece8SMiguel Ojeda /// [`append`]: Vec::append 2239753dece8SMiguel Ojeda /// [`resize`]: Vec::resize 2240753dece8SMiguel Ojeda /// [`resize_with`]: Vec::resize_with 2241753dece8SMiguel Ojeda /// 2242753dece8SMiguel Ojeda /// # Examples 2243753dece8SMiguel Ojeda /// 2244753dece8SMiguel Ojeda /// ``` 2245753dece8SMiguel Ojeda /// #![feature(vec_split_at_spare)] 2246753dece8SMiguel Ojeda /// 2247753dece8SMiguel Ojeda /// let mut v = vec![1, 1, 2]; 2248753dece8SMiguel Ojeda /// 2249753dece8SMiguel Ojeda /// // Reserve additional space big enough for 10 elements. 2250753dece8SMiguel Ojeda /// v.reserve(10); 2251753dece8SMiguel Ojeda /// 2252753dece8SMiguel Ojeda /// let (init, uninit) = v.split_at_spare_mut(); 2253753dece8SMiguel Ojeda /// let sum = init.iter().copied().sum::<u32>(); 2254753dece8SMiguel Ojeda /// 2255753dece8SMiguel Ojeda /// // Fill in the next 4 elements. 2256753dece8SMiguel Ojeda /// uninit[0].write(sum); 2257753dece8SMiguel Ojeda /// uninit[1].write(sum * 2); 2258753dece8SMiguel Ojeda /// uninit[2].write(sum * 3); 2259753dece8SMiguel Ojeda /// uninit[3].write(sum * 4); 2260753dece8SMiguel Ojeda /// 2261753dece8SMiguel Ojeda /// // Mark the 4 elements of the vector as being initialized. 2262753dece8SMiguel Ojeda /// unsafe { 2263753dece8SMiguel Ojeda /// let len = v.len(); 2264753dece8SMiguel Ojeda /// v.set_len(len + 4); 2265753dece8SMiguel Ojeda /// } 2266753dece8SMiguel Ojeda /// 2267753dece8SMiguel Ojeda /// assert_eq!(&v, &[1, 1, 2, 4, 8, 12, 16]); 2268753dece8SMiguel Ojeda /// ``` 2269753dece8SMiguel Ojeda #[unstable(feature = "vec_split_at_spare", issue = "81944")] 2270753dece8SMiguel Ojeda #[inline] 2271753dece8SMiguel Ojeda pub fn split_at_spare_mut(&mut self) -> (&mut [T], &mut [MaybeUninit<T>]) { 2272753dece8SMiguel Ojeda // SAFETY: 2273753dece8SMiguel Ojeda // - len is ignored and so never changed 2274753dece8SMiguel Ojeda let (init, spare, _) = unsafe { self.split_at_spare_mut_with_len() }; 2275753dece8SMiguel Ojeda (init, spare) 2276753dece8SMiguel Ojeda } 2277753dece8SMiguel Ojeda 2278753dece8SMiguel Ojeda /// Safety: changing returned .2 (&mut usize) is considered the same as calling `.set_len(_)`. 2279753dece8SMiguel Ojeda /// 2280753dece8SMiguel Ojeda /// This method provides unique access to all vec parts at once in `extend_from_within`. 2281753dece8SMiguel Ojeda unsafe fn split_at_spare_mut_with_len( 2282753dece8SMiguel Ojeda &mut self, 2283753dece8SMiguel Ojeda ) -> (&mut [T], &mut [MaybeUninit<T>], &mut usize) { 2284753dece8SMiguel Ojeda let ptr = self.as_mut_ptr(); 2285753dece8SMiguel Ojeda // SAFETY: 2286753dece8SMiguel Ojeda // - `ptr` is guaranteed to be valid for `self.len` elements 2287753dece8SMiguel Ojeda // - but the allocation extends out to `self.buf.capacity()` elements, possibly 2288753dece8SMiguel Ojeda // uninitialized 2289753dece8SMiguel Ojeda let spare_ptr = unsafe { ptr.add(self.len) }; 2290753dece8SMiguel Ojeda let spare_ptr = spare_ptr.cast::<MaybeUninit<T>>(); 2291753dece8SMiguel Ojeda let spare_len = self.buf.capacity() - self.len; 2292753dece8SMiguel Ojeda 2293753dece8SMiguel Ojeda // SAFETY: 2294753dece8SMiguel Ojeda // - `ptr` is guaranteed to be valid for `self.len` elements 2295753dece8SMiguel Ojeda // - `spare_ptr` is pointing one element past the buffer, so it doesn't overlap with `initialized` 2296753dece8SMiguel Ojeda unsafe { 2297753dece8SMiguel Ojeda let initialized = slice::from_raw_parts_mut(ptr, self.len); 2298753dece8SMiguel Ojeda let spare = slice::from_raw_parts_mut(spare_ptr, spare_len); 2299753dece8SMiguel Ojeda 2300753dece8SMiguel Ojeda (initialized, spare, &mut self.len) 2301753dece8SMiguel Ojeda } 2302753dece8SMiguel Ojeda } 2303753dece8SMiguel Ojeda } 2304753dece8SMiguel Ojeda 2305753dece8SMiguel Ojeda impl<T: Clone, A: Allocator> Vec<T, A> { 2306753dece8SMiguel Ojeda /// Resizes the `Vec` in-place so that `len` is equal to `new_len`. 2307753dece8SMiguel Ojeda /// 2308753dece8SMiguel Ojeda /// If `new_len` is greater than `len`, the `Vec` is extended by the 2309753dece8SMiguel Ojeda /// difference, with each additional slot filled with `value`. 2310753dece8SMiguel Ojeda /// If `new_len` is less than `len`, the `Vec` is simply truncated. 2311753dece8SMiguel Ojeda /// 2312753dece8SMiguel Ojeda /// This method requires `T` to implement [`Clone`], 2313753dece8SMiguel Ojeda /// in order to be able to clone the passed value. 2314753dece8SMiguel Ojeda /// If you need more flexibility (or want to rely on [`Default`] instead of 2315753dece8SMiguel Ojeda /// [`Clone`]), use [`Vec::resize_with`]. 2316753dece8SMiguel Ojeda /// If you only need to resize to a smaller size, use [`Vec::truncate`]. 2317753dece8SMiguel Ojeda /// 2318753dece8SMiguel Ojeda /// # Examples 2319753dece8SMiguel Ojeda /// 2320753dece8SMiguel Ojeda /// ``` 2321753dece8SMiguel Ojeda /// let mut vec = vec!["hello"]; 2322753dece8SMiguel Ojeda /// vec.resize(3, "world"); 2323753dece8SMiguel Ojeda /// assert_eq!(vec, ["hello", "world", "world"]); 2324753dece8SMiguel Ojeda /// 2325753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3, 4]; 2326753dece8SMiguel Ojeda /// vec.resize(2, 0); 2327753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2]); 2328753dece8SMiguel Ojeda /// ``` 2329753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2330753dece8SMiguel Ojeda #[stable(feature = "vec_resize", since = "1.5.0")] 2331753dece8SMiguel Ojeda pub fn resize(&mut self, new_len: usize, value: T) { 2332753dece8SMiguel Ojeda let len = self.len(); 2333753dece8SMiguel Ojeda 2334753dece8SMiguel Ojeda if new_len > len { 2335753dece8SMiguel Ojeda self.extend_with(new_len - len, ExtendElement(value)) 2336753dece8SMiguel Ojeda } else { 2337753dece8SMiguel Ojeda self.truncate(new_len); 2338753dece8SMiguel Ojeda } 2339753dece8SMiguel Ojeda } 2340753dece8SMiguel Ojeda 2341753dece8SMiguel Ojeda /// Clones and appends all elements in a slice to the `Vec`. 2342753dece8SMiguel Ojeda /// 2343753dece8SMiguel Ojeda /// Iterates over the slice `other`, clones each element, and then appends 2344753dece8SMiguel Ojeda /// it to this `Vec`. The `other` slice is traversed in-order. 2345753dece8SMiguel Ojeda /// 2346753dece8SMiguel Ojeda /// Note that this function is same as [`extend`] except that it is 2347753dece8SMiguel Ojeda /// specialized to work with slices instead. If and when Rust gets 2348753dece8SMiguel Ojeda /// specialization this function will likely be deprecated (but still 2349753dece8SMiguel Ojeda /// available). 2350753dece8SMiguel Ojeda /// 2351753dece8SMiguel Ojeda /// # Examples 2352753dece8SMiguel Ojeda /// 2353753dece8SMiguel Ojeda /// ``` 2354753dece8SMiguel Ojeda /// let mut vec = vec![1]; 2355753dece8SMiguel Ojeda /// vec.extend_from_slice(&[2, 3, 4]); 2356753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2, 3, 4]); 2357753dece8SMiguel Ojeda /// ``` 2358753dece8SMiguel Ojeda /// 2359753dece8SMiguel Ojeda /// [`extend`]: Vec::extend 2360753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2361753dece8SMiguel Ojeda #[stable(feature = "vec_extend_from_slice", since = "1.6.0")] 2362753dece8SMiguel Ojeda pub fn extend_from_slice(&mut self, other: &[T]) { 2363753dece8SMiguel Ojeda self.spec_extend(other.iter()) 2364753dece8SMiguel Ojeda } 2365753dece8SMiguel Ojeda 2366753dece8SMiguel Ojeda /// Copies elements from `src` range to the end of the vector. 2367753dece8SMiguel Ojeda /// 2368753dece8SMiguel Ojeda /// # Panics 2369753dece8SMiguel Ojeda /// 2370753dece8SMiguel Ojeda /// Panics if the starting point is greater than the end point or if 2371753dece8SMiguel Ojeda /// the end point is greater than the length of the vector. 2372753dece8SMiguel Ojeda /// 2373753dece8SMiguel Ojeda /// # Examples 2374753dece8SMiguel Ojeda /// 2375753dece8SMiguel Ojeda /// ``` 2376753dece8SMiguel Ojeda /// let mut vec = vec![0, 1, 2, 3, 4]; 2377753dece8SMiguel Ojeda /// 2378753dece8SMiguel Ojeda /// vec.extend_from_within(2..); 2379753dece8SMiguel Ojeda /// assert_eq!(vec, [0, 1, 2, 3, 4, 2, 3, 4]); 2380753dece8SMiguel Ojeda /// 2381753dece8SMiguel Ojeda /// vec.extend_from_within(..2); 2382753dece8SMiguel Ojeda /// assert_eq!(vec, [0, 1, 2, 3, 4, 2, 3, 4, 0, 1]); 2383753dece8SMiguel Ojeda /// 2384753dece8SMiguel Ojeda /// vec.extend_from_within(4..8); 2385753dece8SMiguel Ojeda /// assert_eq!(vec, [0, 1, 2, 3, 4, 2, 3, 4, 0, 1, 4, 2, 3, 4]); 2386753dece8SMiguel Ojeda /// ``` 2387753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2388753dece8SMiguel Ojeda #[stable(feature = "vec_extend_from_within", since = "1.53.0")] 2389753dece8SMiguel Ojeda pub fn extend_from_within<R>(&mut self, src: R) 2390753dece8SMiguel Ojeda where 2391753dece8SMiguel Ojeda R: RangeBounds<usize>, 2392753dece8SMiguel Ojeda { 2393753dece8SMiguel Ojeda let range = slice::range(src, ..self.len()); 2394753dece8SMiguel Ojeda self.reserve(range.len()); 2395753dece8SMiguel Ojeda 2396753dece8SMiguel Ojeda // SAFETY: 2397753dece8SMiguel Ojeda // - `slice::range` guarantees that the given range is valid for indexing self 2398753dece8SMiguel Ojeda unsafe { 2399753dece8SMiguel Ojeda self.spec_extend_from_within(range); 2400753dece8SMiguel Ojeda } 2401753dece8SMiguel Ojeda } 2402753dece8SMiguel Ojeda } 2403753dece8SMiguel Ojeda 2404753dece8SMiguel Ojeda impl<T, A: Allocator, const N: usize> Vec<[T; N], A> { 2405753dece8SMiguel Ojeda /// Takes a `Vec<[T; N]>` and flattens it into a `Vec<T>`. 2406753dece8SMiguel Ojeda /// 2407753dece8SMiguel Ojeda /// # Panics 2408753dece8SMiguel Ojeda /// 2409753dece8SMiguel Ojeda /// Panics if the length of the resulting vector would overflow a `usize`. 2410753dece8SMiguel Ojeda /// 2411753dece8SMiguel Ojeda /// This is only possible when flattening a vector of arrays of zero-sized 2412753dece8SMiguel Ojeda /// types, and thus tends to be irrelevant in practice. If 2413753dece8SMiguel Ojeda /// `size_of::<T>() > 0`, this will never panic. 2414753dece8SMiguel Ojeda /// 2415753dece8SMiguel Ojeda /// # Examples 2416753dece8SMiguel Ojeda /// 2417753dece8SMiguel Ojeda /// ``` 2418753dece8SMiguel Ojeda /// #![feature(slice_flatten)] 2419753dece8SMiguel Ojeda /// 2420753dece8SMiguel Ojeda /// let mut vec = vec![[1, 2, 3], [4, 5, 6], [7, 8, 9]]; 2421753dece8SMiguel Ojeda /// assert_eq!(vec.pop(), Some([7, 8, 9])); 2422753dece8SMiguel Ojeda /// 2423753dece8SMiguel Ojeda /// let mut flattened = vec.into_flattened(); 2424753dece8SMiguel Ojeda /// assert_eq!(flattened.pop(), Some(6)); 2425753dece8SMiguel Ojeda /// ``` 2426753dece8SMiguel Ojeda #[unstable(feature = "slice_flatten", issue = "95629")] 2427753dece8SMiguel Ojeda pub fn into_flattened(self) -> Vec<T, A> { 2428753dece8SMiguel Ojeda let (ptr, len, cap, alloc) = self.into_raw_parts_with_alloc(); 2429753dece8SMiguel Ojeda let (new_len, new_cap) = if mem::size_of::<T>() == 0 { 2430753dece8SMiguel Ojeda (len.checked_mul(N).expect("vec len overflow"), usize::MAX) 2431753dece8SMiguel Ojeda } else { 2432753dece8SMiguel Ojeda // SAFETY: 2433753dece8SMiguel Ojeda // - `cap * N` cannot overflow because the allocation is already in 2434753dece8SMiguel Ojeda // the address space. 2435753dece8SMiguel Ojeda // - Each `[T; N]` has `N` valid elements, so there are `len * N` 2436753dece8SMiguel Ojeda // valid elements in the allocation. 2437753dece8SMiguel Ojeda unsafe { (len.unchecked_mul(N), cap.unchecked_mul(N)) } 2438753dece8SMiguel Ojeda }; 2439753dece8SMiguel Ojeda // SAFETY: 2440753dece8SMiguel Ojeda // - `ptr` was allocated by `self` 2441753dece8SMiguel Ojeda // - `ptr` is well-aligned because `[T; N]` has the same alignment as `T`. 2442753dece8SMiguel Ojeda // - `new_cap` refers to the same sized allocation as `cap` because 2443753dece8SMiguel Ojeda // `new_cap * size_of::<T>()` == `cap * size_of::<[T; N]>()` 2444753dece8SMiguel Ojeda // - `len` <= `cap`, so `len * N` <= `cap * N`. 2445753dece8SMiguel Ojeda unsafe { Vec::<T, A>::from_raw_parts_in(ptr.cast(), new_len, new_cap, alloc) } 2446753dece8SMiguel Ojeda } 2447753dece8SMiguel Ojeda } 2448753dece8SMiguel Ojeda 2449753dece8SMiguel Ojeda // This code generalizes `extend_with_{element,default}`. 2450753dece8SMiguel Ojeda trait ExtendWith<T> { 2451753dece8SMiguel Ojeda fn next(&mut self) -> T; 2452753dece8SMiguel Ojeda fn last(self) -> T; 2453753dece8SMiguel Ojeda } 2454753dece8SMiguel Ojeda 2455753dece8SMiguel Ojeda struct ExtendElement<T>(T); 2456753dece8SMiguel Ojeda impl<T: Clone> ExtendWith<T> for ExtendElement<T> { 2457753dece8SMiguel Ojeda fn next(&mut self) -> T { 2458753dece8SMiguel Ojeda self.0.clone() 2459753dece8SMiguel Ojeda } 2460753dece8SMiguel Ojeda fn last(self) -> T { 2461753dece8SMiguel Ojeda self.0 2462753dece8SMiguel Ojeda } 2463753dece8SMiguel Ojeda } 2464753dece8SMiguel Ojeda 2465753dece8SMiguel Ojeda struct ExtendFunc<F>(F); 2466753dece8SMiguel Ojeda impl<T, F: FnMut() -> T> ExtendWith<T> for ExtendFunc<F> { 2467753dece8SMiguel Ojeda fn next(&mut self) -> T { 2468753dece8SMiguel Ojeda (self.0)() 2469753dece8SMiguel Ojeda } 2470753dece8SMiguel Ojeda fn last(mut self) -> T { 2471753dece8SMiguel Ojeda (self.0)() 2472753dece8SMiguel Ojeda } 2473753dece8SMiguel Ojeda } 2474753dece8SMiguel Ojeda 2475753dece8SMiguel Ojeda impl<T, A: Allocator> Vec<T, A> { 2476753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2477753dece8SMiguel Ojeda /// Extend the vector by `n` values, using the given generator. 2478753dece8SMiguel Ojeda fn extend_with<E: ExtendWith<T>>(&mut self, n: usize, mut value: E) { 2479753dece8SMiguel Ojeda self.reserve(n); 2480753dece8SMiguel Ojeda 2481753dece8SMiguel Ojeda unsafe { 2482753dece8SMiguel Ojeda let mut ptr = self.as_mut_ptr().add(self.len()); 2483753dece8SMiguel Ojeda // Use SetLenOnDrop to work around bug where compiler 2484753dece8SMiguel Ojeda // might not realize the store through `ptr` through self.set_len() 2485753dece8SMiguel Ojeda // don't alias. 2486753dece8SMiguel Ojeda let mut local_len = SetLenOnDrop::new(&mut self.len); 2487753dece8SMiguel Ojeda 2488753dece8SMiguel Ojeda // Write all elements except the last one 2489753dece8SMiguel Ojeda for _ in 1..n { 2490753dece8SMiguel Ojeda ptr::write(ptr, value.next()); 2491753dece8SMiguel Ojeda ptr = ptr.offset(1); 2492753dece8SMiguel Ojeda // Increment the length in every step in case next() panics 2493753dece8SMiguel Ojeda local_len.increment_len(1); 2494753dece8SMiguel Ojeda } 2495753dece8SMiguel Ojeda 2496753dece8SMiguel Ojeda if n > 0 { 2497753dece8SMiguel Ojeda // We can write the last element directly without cloning needlessly 2498753dece8SMiguel Ojeda ptr::write(ptr, value.last()); 2499753dece8SMiguel Ojeda local_len.increment_len(1); 2500753dece8SMiguel Ojeda } 2501753dece8SMiguel Ojeda 2502753dece8SMiguel Ojeda // len set by scope guard 2503753dece8SMiguel Ojeda } 2504753dece8SMiguel Ojeda } 2505753dece8SMiguel Ojeda } 2506753dece8SMiguel Ojeda 2507753dece8SMiguel Ojeda impl<T: PartialEq, A: Allocator> Vec<T, A> { 2508753dece8SMiguel Ojeda /// Removes consecutive repeated elements in the vector according to the 2509753dece8SMiguel Ojeda /// [`PartialEq`] trait implementation. 2510753dece8SMiguel Ojeda /// 2511753dece8SMiguel Ojeda /// If the vector is sorted, this removes all duplicates. 2512753dece8SMiguel Ojeda /// 2513753dece8SMiguel Ojeda /// # Examples 2514753dece8SMiguel Ojeda /// 2515753dece8SMiguel Ojeda /// ``` 2516753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 2, 3, 2]; 2517753dece8SMiguel Ojeda /// 2518753dece8SMiguel Ojeda /// vec.dedup(); 2519753dece8SMiguel Ojeda /// 2520753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2, 3, 2]); 2521753dece8SMiguel Ojeda /// ``` 2522753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2523753dece8SMiguel Ojeda #[inline] 2524753dece8SMiguel Ojeda pub fn dedup(&mut self) { 2525753dece8SMiguel Ojeda self.dedup_by(|a, b| a == b) 2526753dece8SMiguel Ojeda } 2527753dece8SMiguel Ojeda } 2528753dece8SMiguel Ojeda 2529753dece8SMiguel Ojeda //////////////////////////////////////////////////////////////////////////////// 2530753dece8SMiguel Ojeda // Internal methods and functions 2531753dece8SMiguel Ojeda //////////////////////////////////////////////////////////////////////////////// 2532753dece8SMiguel Ojeda 2533753dece8SMiguel Ojeda #[doc(hidden)] 2534753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2535753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2536753dece8SMiguel Ojeda pub fn from_elem<T: Clone>(elem: T, n: usize) -> Vec<T> { 2537753dece8SMiguel Ojeda <T as SpecFromElem>::from_elem(elem, n, Global) 2538753dece8SMiguel Ojeda } 2539753dece8SMiguel Ojeda 2540753dece8SMiguel Ojeda #[doc(hidden)] 2541753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2542753dece8SMiguel Ojeda #[unstable(feature = "allocator_api", issue = "32838")] 2543753dece8SMiguel Ojeda pub fn from_elem_in<T: Clone, A: Allocator>(elem: T, n: usize, alloc: A) -> Vec<T, A> { 2544753dece8SMiguel Ojeda <T as SpecFromElem>::from_elem(elem, n, alloc) 2545753dece8SMiguel Ojeda } 2546753dece8SMiguel Ojeda 2547753dece8SMiguel Ojeda trait ExtendFromWithinSpec { 2548753dece8SMiguel Ojeda /// # Safety 2549753dece8SMiguel Ojeda /// 2550753dece8SMiguel Ojeda /// - `src` needs to be valid index 2551753dece8SMiguel Ojeda /// - `self.capacity() - self.len()` must be `>= src.len()` 2552753dece8SMiguel Ojeda unsafe fn spec_extend_from_within(&mut self, src: Range<usize>); 2553753dece8SMiguel Ojeda } 2554753dece8SMiguel Ojeda 2555753dece8SMiguel Ojeda impl<T: Clone, A: Allocator> ExtendFromWithinSpec for Vec<T, A> { 2556753dece8SMiguel Ojeda default unsafe fn spec_extend_from_within(&mut self, src: Range<usize>) { 2557753dece8SMiguel Ojeda // SAFETY: 2558753dece8SMiguel Ojeda // - len is increased only after initializing elements 2559753dece8SMiguel Ojeda let (this, spare, len) = unsafe { self.split_at_spare_mut_with_len() }; 2560753dece8SMiguel Ojeda 2561753dece8SMiguel Ojeda // SAFETY: 2562753dece8SMiguel Ojeda // - caller guaratees that src is a valid index 2563753dece8SMiguel Ojeda let to_clone = unsafe { this.get_unchecked(src) }; 2564753dece8SMiguel Ojeda 2565753dece8SMiguel Ojeda iter::zip(to_clone, spare) 2566753dece8SMiguel Ojeda .map(|(src, dst)| dst.write(src.clone())) 2567753dece8SMiguel Ojeda // Note: 2568753dece8SMiguel Ojeda // - Element was just initialized with `MaybeUninit::write`, so it's ok to increase len 2569753dece8SMiguel Ojeda // - len is increased after each element to prevent leaks (see issue #82533) 2570753dece8SMiguel Ojeda .for_each(|_| *len += 1); 2571753dece8SMiguel Ojeda } 2572753dece8SMiguel Ojeda } 2573753dece8SMiguel Ojeda 2574753dece8SMiguel Ojeda impl<T: Copy, A: Allocator> ExtendFromWithinSpec for Vec<T, A> { 2575753dece8SMiguel Ojeda unsafe fn spec_extend_from_within(&mut self, src: Range<usize>) { 2576753dece8SMiguel Ojeda let count = src.len(); 2577753dece8SMiguel Ojeda { 2578753dece8SMiguel Ojeda let (init, spare) = self.split_at_spare_mut(); 2579753dece8SMiguel Ojeda 2580753dece8SMiguel Ojeda // SAFETY: 2581753dece8SMiguel Ojeda // - caller guaratees that `src` is a valid index 2582753dece8SMiguel Ojeda let source = unsafe { init.get_unchecked(src) }; 2583753dece8SMiguel Ojeda 2584753dece8SMiguel Ojeda // SAFETY: 2585753dece8SMiguel Ojeda // - Both pointers are created from unique slice references (`&mut [_]`) 2586753dece8SMiguel Ojeda // so they are valid and do not overlap. 2587753dece8SMiguel Ojeda // - Elements are :Copy so it's OK to to copy them, without doing 2588753dece8SMiguel Ojeda // anything with the original values 2589753dece8SMiguel Ojeda // - `count` is equal to the len of `source`, so source is valid for 2590753dece8SMiguel Ojeda // `count` reads 2591753dece8SMiguel Ojeda // - `.reserve(count)` guarantees that `spare.len() >= count` so spare 2592753dece8SMiguel Ojeda // is valid for `count` writes 2593753dece8SMiguel Ojeda unsafe { ptr::copy_nonoverlapping(source.as_ptr(), spare.as_mut_ptr() as _, count) }; 2594753dece8SMiguel Ojeda } 2595753dece8SMiguel Ojeda 2596753dece8SMiguel Ojeda // SAFETY: 2597753dece8SMiguel Ojeda // - The elements were just initialized by `copy_nonoverlapping` 2598753dece8SMiguel Ojeda self.len += count; 2599753dece8SMiguel Ojeda } 2600753dece8SMiguel Ojeda } 2601753dece8SMiguel Ojeda 2602753dece8SMiguel Ojeda //////////////////////////////////////////////////////////////////////////////// 2603753dece8SMiguel Ojeda // Common trait implementations for Vec 2604753dece8SMiguel Ojeda //////////////////////////////////////////////////////////////////////////////// 2605753dece8SMiguel Ojeda 2606753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2607753dece8SMiguel Ojeda impl<T, A: Allocator> ops::Deref for Vec<T, A> { 2608753dece8SMiguel Ojeda type Target = [T]; 2609753dece8SMiguel Ojeda 2610753dece8SMiguel Ojeda fn deref(&self) -> &[T] { 2611753dece8SMiguel Ojeda unsafe { slice::from_raw_parts(self.as_ptr(), self.len) } 2612753dece8SMiguel Ojeda } 2613753dece8SMiguel Ojeda } 2614753dece8SMiguel Ojeda 2615753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2616753dece8SMiguel Ojeda impl<T, A: Allocator> ops::DerefMut for Vec<T, A> { 2617753dece8SMiguel Ojeda fn deref_mut(&mut self) -> &mut [T] { 2618753dece8SMiguel Ojeda unsafe { slice::from_raw_parts_mut(self.as_mut_ptr(), self.len) } 2619753dece8SMiguel Ojeda } 2620753dece8SMiguel Ojeda } 2621753dece8SMiguel Ojeda 2622753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2623753dece8SMiguel Ojeda trait SpecCloneFrom { 2624753dece8SMiguel Ojeda fn clone_from(this: &mut Self, other: &Self); 2625753dece8SMiguel Ojeda } 2626753dece8SMiguel Ojeda 2627753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2628753dece8SMiguel Ojeda impl<T: Clone, A: Allocator> SpecCloneFrom for Vec<T, A> { 2629753dece8SMiguel Ojeda default fn clone_from(this: &mut Self, other: &Self) { 2630753dece8SMiguel Ojeda // drop anything that will not be overwritten 2631753dece8SMiguel Ojeda this.truncate(other.len()); 2632753dece8SMiguel Ojeda 2633753dece8SMiguel Ojeda // self.len <= other.len due to the truncate above, so the 2634753dece8SMiguel Ojeda // slices here are always in-bounds. 2635753dece8SMiguel Ojeda let (init, tail) = other.split_at(this.len()); 2636753dece8SMiguel Ojeda 2637753dece8SMiguel Ojeda // reuse the contained values' allocations/resources. 2638753dece8SMiguel Ojeda this.clone_from_slice(init); 2639753dece8SMiguel Ojeda this.extend_from_slice(tail); 2640753dece8SMiguel Ojeda } 2641753dece8SMiguel Ojeda } 2642753dece8SMiguel Ojeda 2643753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2644753dece8SMiguel Ojeda impl<T: Copy, A: Allocator> SpecCloneFrom for Vec<T, A> { 2645753dece8SMiguel Ojeda fn clone_from(this: &mut Self, other: &Self) { 2646753dece8SMiguel Ojeda this.clear(); 2647753dece8SMiguel Ojeda this.extend_from_slice(other); 2648753dece8SMiguel Ojeda } 2649753dece8SMiguel Ojeda } 2650753dece8SMiguel Ojeda 2651753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2652753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2653753dece8SMiguel Ojeda impl<T: Clone, A: Allocator + Clone> Clone for Vec<T, A> { 2654753dece8SMiguel Ojeda #[cfg(not(test))] 2655753dece8SMiguel Ojeda fn clone(&self) -> Self { 2656753dece8SMiguel Ojeda let alloc = self.allocator().clone(); 2657753dece8SMiguel Ojeda <[T]>::to_vec_in(&**self, alloc) 2658753dece8SMiguel Ojeda } 2659753dece8SMiguel Ojeda 2660753dece8SMiguel Ojeda // HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is 2661753dece8SMiguel Ojeda // required for this method definition, is not available. Instead use the 2662753dece8SMiguel Ojeda // `slice::to_vec` function which is only available with cfg(test) 2663753dece8SMiguel Ojeda // NB see the slice::hack module in slice.rs for more information 2664753dece8SMiguel Ojeda #[cfg(test)] 2665753dece8SMiguel Ojeda fn clone(&self) -> Self { 2666753dece8SMiguel Ojeda let alloc = self.allocator().clone(); 2667753dece8SMiguel Ojeda crate::slice::to_vec(&**self, alloc) 2668753dece8SMiguel Ojeda } 2669753dece8SMiguel Ojeda 2670753dece8SMiguel Ojeda fn clone_from(&mut self, other: &Self) { 2671753dece8SMiguel Ojeda SpecCloneFrom::clone_from(self, other) 2672753dece8SMiguel Ojeda } 2673753dece8SMiguel Ojeda } 2674753dece8SMiguel Ojeda 2675753dece8SMiguel Ojeda /// The hash of a vector is the same as that of the corresponding slice, 2676753dece8SMiguel Ojeda /// as required by the `core::borrow::Borrow` implementation. 2677753dece8SMiguel Ojeda /// 2678753dece8SMiguel Ojeda /// ``` 2679753dece8SMiguel Ojeda /// #![feature(build_hasher_simple_hash_one)] 2680753dece8SMiguel Ojeda /// use std::hash::BuildHasher; 2681753dece8SMiguel Ojeda /// 2682753dece8SMiguel Ojeda /// let b = std::collections::hash_map::RandomState::new(); 2683753dece8SMiguel Ojeda /// let v: Vec<u8> = vec![0xa8, 0x3c, 0x09]; 2684753dece8SMiguel Ojeda /// let s: &[u8] = &[0xa8, 0x3c, 0x09]; 2685753dece8SMiguel Ojeda /// assert_eq!(b.hash_one(v), b.hash_one(s)); 2686753dece8SMiguel Ojeda /// ``` 2687753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2688753dece8SMiguel Ojeda impl<T: Hash, A: Allocator> Hash for Vec<T, A> { 2689753dece8SMiguel Ojeda #[inline] 2690753dece8SMiguel Ojeda fn hash<H: Hasher>(&self, state: &mut H) { 2691753dece8SMiguel Ojeda Hash::hash(&**self, state) 2692753dece8SMiguel Ojeda } 2693753dece8SMiguel Ojeda } 2694753dece8SMiguel Ojeda 2695753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2696753dece8SMiguel Ojeda #[rustc_on_unimplemented( 2697753dece8SMiguel Ojeda message = "vector indices are of type `usize` or ranges of `usize`", 2698753dece8SMiguel Ojeda label = "vector indices are of type `usize` or ranges of `usize`" 2699753dece8SMiguel Ojeda )] 2700753dece8SMiguel Ojeda impl<T, I: SliceIndex<[T]>, A: Allocator> Index<I> for Vec<T, A> { 2701753dece8SMiguel Ojeda type Output = I::Output; 2702753dece8SMiguel Ojeda 2703753dece8SMiguel Ojeda #[inline] 2704753dece8SMiguel Ojeda fn index(&self, index: I) -> &Self::Output { 2705753dece8SMiguel Ojeda Index::index(&**self, index) 2706753dece8SMiguel Ojeda } 2707753dece8SMiguel Ojeda } 2708753dece8SMiguel Ojeda 2709753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2710753dece8SMiguel Ojeda #[rustc_on_unimplemented( 2711753dece8SMiguel Ojeda message = "vector indices are of type `usize` or ranges of `usize`", 2712753dece8SMiguel Ojeda label = "vector indices are of type `usize` or ranges of `usize`" 2713753dece8SMiguel Ojeda )] 2714753dece8SMiguel Ojeda impl<T, I: SliceIndex<[T]>, A: Allocator> IndexMut<I> for Vec<T, A> { 2715753dece8SMiguel Ojeda #[inline] 2716753dece8SMiguel Ojeda fn index_mut(&mut self, index: I) -> &mut Self::Output { 2717753dece8SMiguel Ojeda IndexMut::index_mut(&mut **self, index) 2718753dece8SMiguel Ojeda } 2719753dece8SMiguel Ojeda } 2720753dece8SMiguel Ojeda 2721753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2722753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2723753dece8SMiguel Ojeda impl<T> FromIterator<T> for Vec<T> { 2724753dece8SMiguel Ojeda #[inline] 2725753dece8SMiguel Ojeda fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Vec<T> { 2726753dece8SMiguel Ojeda <Self as SpecFromIter<T, I::IntoIter>>::from_iter(iter.into_iter()) 2727753dece8SMiguel Ojeda } 2728753dece8SMiguel Ojeda } 2729753dece8SMiguel Ojeda 2730753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2731753dece8SMiguel Ojeda impl<T, A: Allocator> IntoIterator for Vec<T, A> { 2732753dece8SMiguel Ojeda type Item = T; 2733753dece8SMiguel Ojeda type IntoIter = IntoIter<T, A>; 2734753dece8SMiguel Ojeda 2735753dece8SMiguel Ojeda /// Creates a consuming iterator, that is, one that moves each value out of 2736753dece8SMiguel Ojeda /// the vector (from start to end). The vector cannot be used after calling 2737753dece8SMiguel Ojeda /// this. 2738753dece8SMiguel Ojeda /// 2739753dece8SMiguel Ojeda /// # Examples 2740753dece8SMiguel Ojeda /// 2741753dece8SMiguel Ojeda /// ``` 2742753dece8SMiguel Ojeda /// let v = vec!["a".to_string(), "b".to_string()]; 2743753dece8SMiguel Ojeda /// for s in v.into_iter() { 2744753dece8SMiguel Ojeda /// // s has type String, not &String 2745753dece8SMiguel Ojeda /// println!("{s}"); 2746753dece8SMiguel Ojeda /// } 2747753dece8SMiguel Ojeda /// ``` 2748753dece8SMiguel Ojeda #[inline] 2749753dece8SMiguel Ojeda fn into_iter(self) -> IntoIter<T, A> { 2750753dece8SMiguel Ojeda unsafe { 2751753dece8SMiguel Ojeda let mut me = ManuallyDrop::new(self); 2752753dece8SMiguel Ojeda let alloc = ManuallyDrop::new(ptr::read(me.allocator())); 2753753dece8SMiguel Ojeda let begin = me.as_mut_ptr(); 2754753dece8SMiguel Ojeda let end = if mem::size_of::<T>() == 0 { 2755753dece8SMiguel Ojeda arith_offset(begin as *const i8, me.len() as isize) as *const T 2756753dece8SMiguel Ojeda } else { 2757753dece8SMiguel Ojeda begin.add(me.len()) as *const T 2758753dece8SMiguel Ojeda }; 2759753dece8SMiguel Ojeda let cap = me.buf.capacity(); 2760753dece8SMiguel Ojeda IntoIter { 2761753dece8SMiguel Ojeda buf: NonNull::new_unchecked(begin), 2762753dece8SMiguel Ojeda phantom: PhantomData, 2763753dece8SMiguel Ojeda cap, 2764753dece8SMiguel Ojeda alloc, 2765753dece8SMiguel Ojeda ptr: begin, 2766753dece8SMiguel Ojeda end, 2767753dece8SMiguel Ojeda } 2768753dece8SMiguel Ojeda } 2769753dece8SMiguel Ojeda } 2770753dece8SMiguel Ojeda } 2771753dece8SMiguel Ojeda 2772753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2773753dece8SMiguel Ojeda impl<'a, T, A: Allocator> IntoIterator for &'a Vec<T, A> { 2774753dece8SMiguel Ojeda type Item = &'a T; 2775753dece8SMiguel Ojeda type IntoIter = slice::Iter<'a, T>; 2776753dece8SMiguel Ojeda 2777753dece8SMiguel Ojeda fn into_iter(self) -> slice::Iter<'a, T> { 2778753dece8SMiguel Ojeda self.iter() 2779753dece8SMiguel Ojeda } 2780753dece8SMiguel Ojeda } 2781753dece8SMiguel Ojeda 2782753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2783753dece8SMiguel Ojeda impl<'a, T, A: Allocator> IntoIterator for &'a mut Vec<T, A> { 2784753dece8SMiguel Ojeda type Item = &'a mut T; 2785753dece8SMiguel Ojeda type IntoIter = slice::IterMut<'a, T>; 2786753dece8SMiguel Ojeda 2787753dece8SMiguel Ojeda fn into_iter(self) -> slice::IterMut<'a, T> { 2788753dece8SMiguel Ojeda self.iter_mut() 2789753dece8SMiguel Ojeda } 2790753dece8SMiguel Ojeda } 2791753dece8SMiguel Ojeda 2792753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2793753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2794753dece8SMiguel Ojeda impl<T, A: Allocator> Extend<T> for Vec<T, A> { 2795753dece8SMiguel Ojeda #[inline] 2796753dece8SMiguel Ojeda fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) { 2797753dece8SMiguel Ojeda <Self as SpecExtend<T, I::IntoIter>>::spec_extend(self, iter.into_iter()) 2798753dece8SMiguel Ojeda } 2799753dece8SMiguel Ojeda 2800753dece8SMiguel Ojeda #[inline] 2801753dece8SMiguel Ojeda fn extend_one(&mut self, item: T) { 2802753dece8SMiguel Ojeda self.push(item); 2803753dece8SMiguel Ojeda } 2804753dece8SMiguel Ojeda 2805753dece8SMiguel Ojeda #[inline] 2806753dece8SMiguel Ojeda fn extend_reserve(&mut self, additional: usize) { 2807753dece8SMiguel Ojeda self.reserve(additional); 2808753dece8SMiguel Ojeda } 2809753dece8SMiguel Ojeda } 2810753dece8SMiguel Ojeda 2811753dece8SMiguel Ojeda impl<T, A: Allocator> Vec<T, A> { 2812753dece8SMiguel Ojeda // leaf method to which various SpecFrom/SpecExtend implementations delegate when 2813753dece8SMiguel Ojeda // they have no further optimizations to apply 2814753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2815753dece8SMiguel Ojeda fn extend_desugared<I: Iterator<Item = T>>(&mut self, mut iterator: I) { 2816753dece8SMiguel Ojeda // This is the case for a general iterator. 2817753dece8SMiguel Ojeda // 2818753dece8SMiguel Ojeda // This function should be the moral equivalent of: 2819753dece8SMiguel Ojeda // 2820753dece8SMiguel Ojeda // for item in iterator { 2821753dece8SMiguel Ojeda // self.push(item); 2822753dece8SMiguel Ojeda // } 2823753dece8SMiguel Ojeda while let Some(element) = iterator.next() { 2824753dece8SMiguel Ojeda let len = self.len(); 2825753dece8SMiguel Ojeda if len == self.capacity() { 2826753dece8SMiguel Ojeda let (lower, _) = iterator.size_hint(); 2827753dece8SMiguel Ojeda self.reserve(lower.saturating_add(1)); 2828753dece8SMiguel Ojeda } 2829753dece8SMiguel Ojeda unsafe { 2830753dece8SMiguel Ojeda ptr::write(self.as_mut_ptr().add(len), element); 2831753dece8SMiguel Ojeda // Since next() executes user code which can panic we have to bump the length 2832753dece8SMiguel Ojeda // after each step. 2833753dece8SMiguel Ojeda // NB can't overflow since we would have had to alloc the address space 2834753dece8SMiguel Ojeda self.set_len(len + 1); 2835753dece8SMiguel Ojeda } 2836753dece8SMiguel Ojeda } 2837753dece8SMiguel Ojeda } 2838753dece8SMiguel Ojeda 2839753dece8SMiguel Ojeda /// Creates a splicing iterator that replaces the specified range in the vector 2840753dece8SMiguel Ojeda /// with the given `replace_with` iterator and yields the removed items. 2841753dece8SMiguel Ojeda /// `replace_with` does not need to be the same length as `range`. 2842753dece8SMiguel Ojeda /// 2843753dece8SMiguel Ojeda /// `range` is removed even if the iterator is not consumed until the end. 2844753dece8SMiguel Ojeda /// 2845753dece8SMiguel Ojeda /// It is unspecified how many elements are removed from the vector 2846753dece8SMiguel Ojeda /// if the `Splice` value is leaked. 2847753dece8SMiguel Ojeda /// 2848753dece8SMiguel Ojeda /// The input iterator `replace_with` is only consumed when the `Splice` value is dropped. 2849753dece8SMiguel Ojeda /// 2850753dece8SMiguel Ojeda /// This is optimal if: 2851753dece8SMiguel Ojeda /// 2852753dece8SMiguel Ojeda /// * The tail (elements in the vector after `range`) is empty, 2853753dece8SMiguel Ojeda /// * or `replace_with` yields fewer or equal elements than `range`’s length 2854753dece8SMiguel Ojeda /// * or the lower bound of its `size_hint()` is exact. 2855753dece8SMiguel Ojeda /// 2856753dece8SMiguel Ojeda /// Otherwise, a temporary vector is allocated and the tail is moved twice. 2857753dece8SMiguel Ojeda /// 2858753dece8SMiguel Ojeda /// # Panics 2859753dece8SMiguel Ojeda /// 2860753dece8SMiguel Ojeda /// Panics if the starting point is greater than the end point or if 2861753dece8SMiguel Ojeda /// the end point is greater than the length of the vector. 2862753dece8SMiguel Ojeda /// 2863753dece8SMiguel Ojeda /// # Examples 2864753dece8SMiguel Ojeda /// 2865753dece8SMiguel Ojeda /// ``` 2866753dece8SMiguel Ojeda /// let mut v = vec![1, 2, 3, 4]; 2867753dece8SMiguel Ojeda /// let new = [7, 8, 9]; 2868753dece8SMiguel Ojeda /// let u: Vec<_> = v.splice(1..3, new).collect(); 2869753dece8SMiguel Ojeda /// assert_eq!(v, &[1, 7, 8, 9, 4]); 2870753dece8SMiguel Ojeda /// assert_eq!(u, &[2, 3]); 2871753dece8SMiguel Ojeda /// ``` 2872753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2873753dece8SMiguel Ojeda #[inline] 2874753dece8SMiguel Ojeda #[stable(feature = "vec_splice", since = "1.21.0")] 2875753dece8SMiguel Ojeda pub fn splice<R, I>(&mut self, range: R, replace_with: I) -> Splice<'_, I::IntoIter, A> 2876753dece8SMiguel Ojeda where 2877753dece8SMiguel Ojeda R: RangeBounds<usize>, 2878753dece8SMiguel Ojeda I: IntoIterator<Item = T>, 2879753dece8SMiguel Ojeda { 2880753dece8SMiguel Ojeda Splice { drain: self.drain(range), replace_with: replace_with.into_iter() } 2881753dece8SMiguel Ojeda } 2882753dece8SMiguel Ojeda 2883753dece8SMiguel Ojeda /// Creates an iterator which uses a closure to determine if an element should be removed. 2884753dece8SMiguel Ojeda /// 2885753dece8SMiguel Ojeda /// If the closure returns true, then the element is removed and yielded. 2886753dece8SMiguel Ojeda /// If the closure returns false, the element will remain in the vector and will not be yielded 2887753dece8SMiguel Ojeda /// by the iterator. 2888753dece8SMiguel Ojeda /// 2889753dece8SMiguel Ojeda /// Using this method is equivalent to the following code: 2890753dece8SMiguel Ojeda /// 2891753dece8SMiguel Ojeda /// ``` 2892753dece8SMiguel Ojeda /// # let some_predicate = |x: &mut i32| { *x == 2 || *x == 3 || *x == 6 }; 2893753dece8SMiguel Ojeda /// # let mut vec = vec![1, 2, 3, 4, 5, 6]; 2894753dece8SMiguel Ojeda /// let mut i = 0; 2895753dece8SMiguel Ojeda /// while i < vec.len() { 2896753dece8SMiguel Ojeda /// if some_predicate(&mut vec[i]) { 2897753dece8SMiguel Ojeda /// let val = vec.remove(i); 2898753dece8SMiguel Ojeda /// // your code here 2899753dece8SMiguel Ojeda /// } else { 2900753dece8SMiguel Ojeda /// i += 1; 2901753dece8SMiguel Ojeda /// } 2902753dece8SMiguel Ojeda /// } 2903753dece8SMiguel Ojeda /// 2904753dece8SMiguel Ojeda /// # assert_eq!(vec, vec![1, 4, 5]); 2905753dece8SMiguel Ojeda /// ``` 2906753dece8SMiguel Ojeda /// 2907753dece8SMiguel Ojeda /// But `drain_filter` is easier to use. `drain_filter` is also more efficient, 2908753dece8SMiguel Ojeda /// because it can backshift the elements of the array in bulk. 2909753dece8SMiguel Ojeda /// 2910753dece8SMiguel Ojeda /// Note that `drain_filter` also lets you mutate every element in the filter closure, 2911753dece8SMiguel Ojeda /// regardless of whether you choose to keep or remove it. 2912753dece8SMiguel Ojeda /// 2913753dece8SMiguel Ojeda /// # Examples 2914753dece8SMiguel Ojeda /// 2915753dece8SMiguel Ojeda /// Splitting an array into evens and odds, reusing the original allocation: 2916753dece8SMiguel Ojeda /// 2917753dece8SMiguel Ojeda /// ``` 2918753dece8SMiguel Ojeda /// #![feature(drain_filter)] 2919753dece8SMiguel Ojeda /// let mut numbers = vec![1, 2, 3, 4, 5, 6, 8, 9, 11, 13, 14, 15]; 2920753dece8SMiguel Ojeda /// 2921753dece8SMiguel Ojeda /// let evens = numbers.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>(); 2922753dece8SMiguel Ojeda /// let odds = numbers; 2923753dece8SMiguel Ojeda /// 2924753dece8SMiguel Ojeda /// assert_eq!(evens, vec![2, 4, 6, 8, 14]); 2925753dece8SMiguel Ojeda /// assert_eq!(odds, vec![1, 3, 5, 9, 11, 13, 15]); 2926753dece8SMiguel Ojeda /// ``` 2927753dece8SMiguel Ojeda #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")] 2928753dece8SMiguel Ojeda pub fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<'_, T, F, A> 2929753dece8SMiguel Ojeda where 2930753dece8SMiguel Ojeda F: FnMut(&mut T) -> bool, 2931753dece8SMiguel Ojeda { 2932753dece8SMiguel Ojeda let old_len = self.len(); 2933753dece8SMiguel Ojeda 2934753dece8SMiguel Ojeda // Guard against us getting leaked (leak amplification) 2935753dece8SMiguel Ojeda unsafe { 2936753dece8SMiguel Ojeda self.set_len(0); 2937753dece8SMiguel Ojeda } 2938753dece8SMiguel Ojeda 2939753dece8SMiguel Ojeda DrainFilter { vec: self, idx: 0, del: 0, old_len, pred: filter, panic_flag: false } 2940753dece8SMiguel Ojeda } 2941753dece8SMiguel Ojeda } 2942753dece8SMiguel Ojeda 2943753dece8SMiguel Ojeda /// Extend implementation that copies elements out of references before pushing them onto the Vec. 2944753dece8SMiguel Ojeda /// 2945753dece8SMiguel Ojeda /// This implementation is specialized for slice iterators, where it uses [`copy_from_slice`] to 2946753dece8SMiguel Ojeda /// append the entire slice at once. 2947753dece8SMiguel Ojeda /// 2948753dece8SMiguel Ojeda /// [`copy_from_slice`]: slice::copy_from_slice 2949753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2950753dece8SMiguel Ojeda #[stable(feature = "extend_ref", since = "1.2.0")] 2951753dece8SMiguel Ojeda impl<'a, T: Copy + 'a, A: Allocator + 'a> Extend<&'a T> for Vec<T, A> { 2952753dece8SMiguel Ojeda fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) { 2953753dece8SMiguel Ojeda self.spec_extend(iter.into_iter()) 2954753dece8SMiguel Ojeda } 2955753dece8SMiguel Ojeda 2956753dece8SMiguel Ojeda #[inline] 2957753dece8SMiguel Ojeda fn extend_one(&mut self, &item: &'a T) { 2958753dece8SMiguel Ojeda self.push(item); 2959753dece8SMiguel Ojeda } 2960753dece8SMiguel Ojeda 2961753dece8SMiguel Ojeda #[inline] 2962753dece8SMiguel Ojeda fn extend_reserve(&mut self, additional: usize) { 2963753dece8SMiguel Ojeda self.reserve(additional); 2964753dece8SMiguel Ojeda } 2965753dece8SMiguel Ojeda } 2966753dece8SMiguel Ojeda 2967753dece8SMiguel Ojeda /// Implements comparison of vectors, [lexicographically](core::cmp::Ord#lexicographical-comparison). 2968753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2969753dece8SMiguel Ojeda impl<T: PartialOrd, A: Allocator> PartialOrd for Vec<T, A> { 2970753dece8SMiguel Ojeda #[inline] 2971753dece8SMiguel Ojeda fn partial_cmp(&self, other: &Self) -> Option<Ordering> { 2972753dece8SMiguel Ojeda PartialOrd::partial_cmp(&**self, &**other) 2973753dece8SMiguel Ojeda } 2974753dece8SMiguel Ojeda } 2975753dece8SMiguel Ojeda 2976753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2977753dece8SMiguel Ojeda impl<T: Eq, A: Allocator> Eq for Vec<T, A> {} 2978753dece8SMiguel Ojeda 2979753dece8SMiguel Ojeda /// Implements ordering of vectors, [lexicographically](core::cmp::Ord#lexicographical-comparison). 2980753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2981753dece8SMiguel Ojeda impl<T: Ord, A: Allocator> Ord for Vec<T, A> { 2982753dece8SMiguel Ojeda #[inline] 2983753dece8SMiguel Ojeda fn cmp(&self, other: &Self) -> Ordering { 2984753dece8SMiguel Ojeda Ord::cmp(&**self, &**other) 2985753dece8SMiguel Ojeda } 2986753dece8SMiguel Ojeda } 2987753dece8SMiguel Ojeda 2988753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2989753dece8SMiguel Ojeda unsafe impl<#[may_dangle] T, A: Allocator> Drop for Vec<T, A> { 2990753dece8SMiguel Ojeda fn drop(&mut self) { 2991753dece8SMiguel Ojeda unsafe { 2992753dece8SMiguel Ojeda // use drop for [T] 2993753dece8SMiguel Ojeda // use a raw slice to refer to the elements of the vector as weakest necessary type; 2994753dece8SMiguel Ojeda // could avoid questions of validity in certain cases 2995753dece8SMiguel Ojeda ptr::drop_in_place(ptr::slice_from_raw_parts_mut(self.as_mut_ptr(), self.len)) 2996753dece8SMiguel Ojeda } 2997753dece8SMiguel Ojeda // RawVec handles deallocation 2998753dece8SMiguel Ojeda } 2999753dece8SMiguel Ojeda } 3000753dece8SMiguel Ojeda 3001753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 3002753dece8SMiguel Ojeda #[rustc_const_unstable(feature = "const_default_impls", issue = "87864")] 3003753dece8SMiguel Ojeda impl<T> const Default for Vec<T> { 3004753dece8SMiguel Ojeda /// Creates an empty `Vec<T>`. 3005753dece8SMiguel Ojeda fn default() -> Vec<T> { 3006753dece8SMiguel Ojeda Vec::new() 3007753dece8SMiguel Ojeda } 3008753dece8SMiguel Ojeda } 3009753dece8SMiguel Ojeda 3010753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 3011753dece8SMiguel Ojeda impl<T: fmt::Debug, A: Allocator> fmt::Debug for Vec<T, A> { 3012753dece8SMiguel Ojeda fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { 3013753dece8SMiguel Ojeda fmt::Debug::fmt(&**self, f) 3014753dece8SMiguel Ojeda } 3015753dece8SMiguel Ojeda } 3016753dece8SMiguel Ojeda 3017753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 3018753dece8SMiguel Ojeda impl<T, A: Allocator> AsRef<Vec<T, A>> for Vec<T, A> { 3019753dece8SMiguel Ojeda fn as_ref(&self) -> &Vec<T, A> { 3020753dece8SMiguel Ojeda self 3021753dece8SMiguel Ojeda } 3022753dece8SMiguel Ojeda } 3023753dece8SMiguel Ojeda 3024753dece8SMiguel Ojeda #[stable(feature = "vec_as_mut", since = "1.5.0")] 3025753dece8SMiguel Ojeda impl<T, A: Allocator> AsMut<Vec<T, A>> for Vec<T, A> { 3026753dece8SMiguel Ojeda fn as_mut(&mut self) -> &mut Vec<T, A> { 3027753dece8SMiguel Ojeda self 3028753dece8SMiguel Ojeda } 3029753dece8SMiguel Ojeda } 3030753dece8SMiguel Ojeda 3031753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 3032753dece8SMiguel Ojeda impl<T, A: Allocator> AsRef<[T]> for Vec<T, A> { 3033753dece8SMiguel Ojeda fn as_ref(&self) -> &[T] { 3034753dece8SMiguel Ojeda self 3035753dece8SMiguel Ojeda } 3036753dece8SMiguel Ojeda } 3037753dece8SMiguel Ojeda 3038753dece8SMiguel Ojeda #[stable(feature = "vec_as_mut", since = "1.5.0")] 3039753dece8SMiguel Ojeda impl<T, A: Allocator> AsMut<[T]> for Vec<T, A> { 3040753dece8SMiguel Ojeda fn as_mut(&mut self) -> &mut [T] { 3041753dece8SMiguel Ojeda self 3042753dece8SMiguel Ojeda } 3043753dece8SMiguel Ojeda } 3044753dece8SMiguel Ojeda 3045753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 3046753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 3047753dece8SMiguel Ojeda impl<T: Clone> From<&[T]> for Vec<T> { 3048753dece8SMiguel Ojeda /// Allocate a `Vec<T>` and fill it by cloning `s`'s items. 3049753dece8SMiguel Ojeda /// 3050753dece8SMiguel Ojeda /// # Examples 3051753dece8SMiguel Ojeda /// 3052753dece8SMiguel Ojeda /// ``` 3053753dece8SMiguel Ojeda /// assert_eq!(Vec::from(&[1, 2, 3][..]), vec![1, 2, 3]); 3054753dece8SMiguel Ojeda /// ``` 3055753dece8SMiguel Ojeda #[cfg(not(test))] 3056753dece8SMiguel Ojeda fn from(s: &[T]) -> Vec<T> { 3057753dece8SMiguel Ojeda s.to_vec() 3058753dece8SMiguel Ojeda } 3059753dece8SMiguel Ojeda #[cfg(test)] 3060753dece8SMiguel Ojeda fn from(s: &[T]) -> Vec<T> { 3061753dece8SMiguel Ojeda crate::slice::to_vec(s, Global) 3062753dece8SMiguel Ojeda } 3063753dece8SMiguel Ojeda } 3064753dece8SMiguel Ojeda 3065753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 3066753dece8SMiguel Ojeda #[stable(feature = "vec_from_mut", since = "1.19.0")] 3067753dece8SMiguel Ojeda impl<T: Clone> From<&mut [T]> for Vec<T> { 3068753dece8SMiguel Ojeda /// Allocate a `Vec<T>` and fill it by cloning `s`'s items. 3069753dece8SMiguel Ojeda /// 3070753dece8SMiguel Ojeda /// # Examples 3071753dece8SMiguel Ojeda /// 3072753dece8SMiguel Ojeda /// ``` 3073753dece8SMiguel Ojeda /// assert_eq!(Vec::from(&mut [1, 2, 3][..]), vec![1, 2, 3]); 3074753dece8SMiguel Ojeda /// ``` 3075753dece8SMiguel Ojeda #[cfg(not(test))] 3076753dece8SMiguel Ojeda fn from(s: &mut [T]) -> Vec<T> { 3077753dece8SMiguel Ojeda s.to_vec() 3078753dece8SMiguel Ojeda } 3079753dece8SMiguel Ojeda #[cfg(test)] 3080753dece8SMiguel Ojeda fn from(s: &mut [T]) -> Vec<T> { 3081753dece8SMiguel Ojeda crate::slice::to_vec(s, Global) 3082753dece8SMiguel Ojeda } 3083753dece8SMiguel Ojeda } 3084753dece8SMiguel Ojeda 3085753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 3086753dece8SMiguel Ojeda #[stable(feature = "vec_from_array", since = "1.44.0")] 3087753dece8SMiguel Ojeda impl<T, const N: usize> From<[T; N]> for Vec<T> { 3088753dece8SMiguel Ojeda /// Allocate a `Vec<T>` and move `s`'s items into it. 3089753dece8SMiguel Ojeda /// 3090753dece8SMiguel Ojeda /// # Examples 3091753dece8SMiguel Ojeda /// 3092753dece8SMiguel Ojeda /// ``` 3093753dece8SMiguel Ojeda /// assert_eq!(Vec::from([1, 2, 3]), vec![1, 2, 3]); 3094753dece8SMiguel Ojeda /// ``` 3095753dece8SMiguel Ojeda #[cfg(not(test))] 3096753dece8SMiguel Ojeda fn from(s: [T; N]) -> Vec<T> { 3097753dece8SMiguel Ojeda <[T]>::into_vec(box s) 3098753dece8SMiguel Ojeda } 3099753dece8SMiguel Ojeda 3100753dece8SMiguel Ojeda #[cfg(test)] 3101753dece8SMiguel Ojeda fn from(s: [T; N]) -> Vec<T> { 3102753dece8SMiguel Ojeda crate::slice::into_vec(box s) 3103753dece8SMiguel Ojeda } 3104753dece8SMiguel Ojeda } 3105753dece8SMiguel Ojeda 3106753dece8SMiguel Ojeda #[stable(feature = "vec_from_cow_slice", since = "1.14.0")] 3107753dece8SMiguel Ojeda impl<'a, T> From<Cow<'a, [T]>> for Vec<T> 3108753dece8SMiguel Ojeda where 3109753dece8SMiguel Ojeda [T]: ToOwned<Owned = Vec<T>>, 3110753dece8SMiguel Ojeda { 3111753dece8SMiguel Ojeda /// Convert a clone-on-write slice into a vector. 3112753dece8SMiguel Ojeda /// 3113753dece8SMiguel Ojeda /// If `s` already owns a `Vec<T>`, it will be returned directly. 3114753dece8SMiguel Ojeda /// If `s` is borrowing a slice, a new `Vec<T>` will be allocated and 3115753dece8SMiguel Ojeda /// filled by cloning `s`'s items into it. 3116753dece8SMiguel Ojeda /// 3117753dece8SMiguel Ojeda /// # Examples 3118753dece8SMiguel Ojeda /// 3119753dece8SMiguel Ojeda /// ``` 3120753dece8SMiguel Ojeda /// # use std::borrow::Cow; 3121753dece8SMiguel Ojeda /// let o: Cow<[i32]> = Cow::Owned(vec![1, 2, 3]); 3122753dece8SMiguel Ojeda /// let b: Cow<[i32]> = Cow::Borrowed(&[1, 2, 3]); 3123753dece8SMiguel Ojeda /// assert_eq!(Vec::from(o), Vec::from(b)); 3124753dece8SMiguel Ojeda /// ``` 3125753dece8SMiguel Ojeda fn from(s: Cow<'a, [T]>) -> Vec<T> { 3126753dece8SMiguel Ojeda s.into_owned() 3127753dece8SMiguel Ojeda } 3128753dece8SMiguel Ojeda } 3129753dece8SMiguel Ojeda 3130753dece8SMiguel Ojeda // note: test pulls in libstd, which causes errors here 3131753dece8SMiguel Ojeda #[cfg(not(test))] 3132753dece8SMiguel Ojeda #[stable(feature = "vec_from_box", since = "1.18.0")] 3133753dece8SMiguel Ojeda impl<T, A: Allocator> From<Box<[T], A>> for Vec<T, A> { 3134753dece8SMiguel Ojeda /// Convert a boxed slice into a vector by transferring ownership of 3135753dece8SMiguel Ojeda /// the existing heap allocation. 3136753dece8SMiguel Ojeda /// 3137753dece8SMiguel Ojeda /// # Examples 3138753dece8SMiguel Ojeda /// 3139753dece8SMiguel Ojeda /// ``` 3140753dece8SMiguel Ojeda /// let b: Box<[i32]> = vec![1, 2, 3].into_boxed_slice(); 3141753dece8SMiguel Ojeda /// assert_eq!(Vec::from(b), vec![1, 2, 3]); 3142753dece8SMiguel Ojeda /// ``` 3143753dece8SMiguel Ojeda fn from(s: Box<[T], A>) -> Self { 3144753dece8SMiguel Ojeda s.into_vec() 3145753dece8SMiguel Ojeda } 3146753dece8SMiguel Ojeda } 3147753dece8SMiguel Ojeda 3148753dece8SMiguel Ojeda // note: test pulls in libstd, which causes errors here 3149753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 3150753dece8SMiguel Ojeda #[cfg(not(test))] 3151753dece8SMiguel Ojeda #[stable(feature = "box_from_vec", since = "1.20.0")] 3152753dece8SMiguel Ojeda impl<T, A: Allocator> From<Vec<T, A>> for Box<[T], A> { 3153753dece8SMiguel Ojeda /// Convert a vector into a boxed slice. 3154753dece8SMiguel Ojeda /// 3155753dece8SMiguel Ojeda /// If `v` has excess capacity, its items will be moved into a 3156753dece8SMiguel Ojeda /// newly-allocated buffer with exactly the right capacity. 3157753dece8SMiguel Ojeda /// 3158753dece8SMiguel Ojeda /// # Examples 3159753dece8SMiguel Ojeda /// 3160753dece8SMiguel Ojeda /// ``` 3161753dece8SMiguel Ojeda /// assert_eq!(Box::from(vec![1, 2, 3]), vec![1, 2, 3].into_boxed_slice()); 3162753dece8SMiguel Ojeda /// ``` 3163753dece8SMiguel Ojeda fn from(v: Vec<T, A>) -> Self { 3164753dece8SMiguel Ojeda v.into_boxed_slice() 3165753dece8SMiguel Ojeda } 3166753dece8SMiguel Ojeda } 3167753dece8SMiguel Ojeda 3168753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 3169753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 3170753dece8SMiguel Ojeda impl From<&str> for Vec<u8> { 3171753dece8SMiguel Ojeda /// Allocate a `Vec<u8>` and fill it with a UTF-8 string. 3172753dece8SMiguel Ojeda /// 3173753dece8SMiguel Ojeda /// # Examples 3174753dece8SMiguel Ojeda /// 3175753dece8SMiguel Ojeda /// ``` 3176753dece8SMiguel Ojeda /// assert_eq!(Vec::from("123"), vec![b'1', b'2', b'3']); 3177753dece8SMiguel Ojeda /// ``` 3178753dece8SMiguel Ojeda fn from(s: &str) -> Vec<u8> { 3179753dece8SMiguel Ojeda From::from(s.as_bytes()) 3180753dece8SMiguel Ojeda } 3181753dece8SMiguel Ojeda } 3182753dece8SMiguel Ojeda 3183753dece8SMiguel Ojeda #[stable(feature = "array_try_from_vec", since = "1.48.0")] 3184753dece8SMiguel Ojeda impl<T, A: Allocator, const N: usize> TryFrom<Vec<T, A>> for [T; N] { 3185753dece8SMiguel Ojeda type Error = Vec<T, A>; 3186753dece8SMiguel Ojeda 3187753dece8SMiguel Ojeda /// Gets the entire contents of the `Vec<T>` as an array, 3188753dece8SMiguel Ojeda /// if its size exactly matches that of the requested array. 3189753dece8SMiguel Ojeda /// 3190753dece8SMiguel Ojeda /// # Examples 3191753dece8SMiguel Ojeda /// 3192753dece8SMiguel Ojeda /// ``` 3193753dece8SMiguel Ojeda /// assert_eq!(vec![1, 2, 3].try_into(), Ok([1, 2, 3])); 3194753dece8SMiguel Ojeda /// assert_eq!(<Vec<i32>>::new().try_into(), Ok([])); 3195753dece8SMiguel Ojeda /// ``` 3196753dece8SMiguel Ojeda /// 3197753dece8SMiguel Ojeda /// If the length doesn't match, the input comes back in `Err`: 3198753dece8SMiguel Ojeda /// ``` 3199753dece8SMiguel Ojeda /// let r: Result<[i32; 4], _> = (0..10).collect::<Vec<_>>().try_into(); 3200753dece8SMiguel Ojeda /// assert_eq!(r, Err(vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9])); 3201753dece8SMiguel Ojeda /// ``` 3202753dece8SMiguel Ojeda /// 3203753dece8SMiguel Ojeda /// If you're fine with just getting a prefix of the `Vec<T>`, 3204753dece8SMiguel Ojeda /// you can call [`.truncate(N)`](Vec::truncate) first. 3205753dece8SMiguel Ojeda /// ``` 3206753dece8SMiguel Ojeda /// let mut v = String::from("hello world").into_bytes(); 3207753dece8SMiguel Ojeda /// v.sort(); 3208753dece8SMiguel Ojeda /// v.truncate(2); 3209753dece8SMiguel Ojeda /// let [a, b]: [_; 2] = v.try_into().unwrap(); 3210753dece8SMiguel Ojeda /// assert_eq!(a, b' '); 3211753dece8SMiguel Ojeda /// assert_eq!(b, b'd'); 3212753dece8SMiguel Ojeda /// ``` 3213753dece8SMiguel Ojeda fn try_from(mut vec: Vec<T, A>) -> Result<[T; N], Vec<T, A>> { 3214753dece8SMiguel Ojeda if vec.len() != N { 3215753dece8SMiguel Ojeda return Err(vec); 3216753dece8SMiguel Ojeda } 3217753dece8SMiguel Ojeda 3218753dece8SMiguel Ojeda // SAFETY: `.set_len(0)` is always sound. 3219753dece8SMiguel Ojeda unsafe { vec.set_len(0) }; 3220753dece8SMiguel Ojeda 3221753dece8SMiguel Ojeda // SAFETY: A `Vec`'s pointer is always aligned properly, and 3222753dece8SMiguel Ojeda // the alignment the array needs is the same as the items. 3223753dece8SMiguel Ojeda // We checked earlier that we have sufficient items. 3224753dece8SMiguel Ojeda // The items will not double-drop as the `set_len` 3225753dece8SMiguel Ojeda // tells the `Vec` not to also drop them. 3226753dece8SMiguel Ojeda let array = unsafe { ptr::read(vec.as_ptr() as *const [T; N]) }; 3227753dece8SMiguel Ojeda Ok(array) 3228753dece8SMiguel Ojeda } 3229753dece8SMiguel Ojeda } 3230