1*057b8d25SMiguel Ojeda // SPDX-License-Identifier: Apache-2.0 OR MIT 2*057b8d25SMiguel 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 475753dece8SMiguel Ojeda /// Creates a `Vec<T>` directly from the raw components of another vector. 476753dece8SMiguel Ojeda /// 477753dece8SMiguel Ojeda /// # Safety 478753dece8SMiguel Ojeda /// 479753dece8SMiguel Ojeda /// This is highly unsafe, due to the number of invariants that aren't 480753dece8SMiguel Ojeda /// checked: 481753dece8SMiguel Ojeda /// 482753dece8SMiguel Ojeda /// * `ptr` needs to have been previously allocated via [`String`]/`Vec<T>` 483753dece8SMiguel Ojeda /// (at least, it's highly likely to be incorrect if it wasn't). 484753dece8SMiguel Ojeda /// * `T` needs to have the same alignment as what `ptr` was allocated with. 485753dece8SMiguel Ojeda /// (`T` having a less strict alignment is not sufficient, the alignment really 486753dece8SMiguel Ojeda /// needs to be equal to satisfy the [`dealloc`] requirement that memory must be 487753dece8SMiguel Ojeda /// allocated and deallocated with the same layout.) 488753dece8SMiguel Ojeda /// * The size of `T` times the `capacity` (ie. the allocated size in bytes) needs 489753dece8SMiguel Ojeda /// to be the same size as the pointer was allocated with. (Because similar to 490753dece8SMiguel Ojeda /// alignment, [`dealloc`] must be called with the same layout `size`.) 491753dece8SMiguel Ojeda /// * `length` needs to be less than or equal to `capacity`. 492753dece8SMiguel Ojeda /// 493753dece8SMiguel Ojeda /// Violating these may cause problems like corrupting the allocator's 494753dece8SMiguel Ojeda /// internal data structures. For example it is normally **not** safe 495753dece8SMiguel Ojeda /// to build a `Vec<u8>` from a pointer to a C `char` array with length 496753dece8SMiguel Ojeda /// `size_t`, doing so is only safe if the array was initially allocated by 497753dece8SMiguel Ojeda /// a `Vec` or `String`. 498753dece8SMiguel Ojeda /// It's also not safe to build one from a `Vec<u16>` and its length, because 499753dece8SMiguel Ojeda /// the allocator cares about the alignment, and these two types have different 500753dece8SMiguel Ojeda /// alignments. The buffer was allocated with alignment 2 (for `u16`), but after 501753dece8SMiguel Ojeda /// turning it into a `Vec<u8>` it'll be deallocated with alignment 1. To avoid 502753dece8SMiguel Ojeda /// these issues, it is often preferable to do casting/transmuting using 503753dece8SMiguel Ojeda /// [`slice::from_raw_parts`] instead. 504753dece8SMiguel Ojeda /// 505753dece8SMiguel Ojeda /// The ownership of `ptr` is effectively transferred to the 506753dece8SMiguel Ojeda /// `Vec<T>` which may then deallocate, reallocate or change the 507753dece8SMiguel Ojeda /// contents of memory pointed to by the pointer at will. Ensure 508753dece8SMiguel Ojeda /// that nothing else uses the pointer after calling this 509753dece8SMiguel Ojeda /// function. 510753dece8SMiguel Ojeda /// 511753dece8SMiguel Ojeda /// [`String`]: crate::string::String 512753dece8SMiguel Ojeda /// [`dealloc`]: crate::alloc::GlobalAlloc::dealloc 513753dece8SMiguel Ojeda /// 514753dece8SMiguel Ojeda /// # Examples 515753dece8SMiguel Ojeda /// 516753dece8SMiguel Ojeda /// ``` 517753dece8SMiguel Ojeda /// use std::ptr; 518753dece8SMiguel Ojeda /// use std::mem; 519753dece8SMiguel Ojeda /// 520753dece8SMiguel Ojeda /// let v = vec![1, 2, 3]; 521753dece8SMiguel Ojeda /// 522753dece8SMiguel Ojeda // FIXME Update this when vec_into_raw_parts is stabilized 523753dece8SMiguel Ojeda /// // Prevent running `v`'s destructor so we are in complete control 524753dece8SMiguel Ojeda /// // of the allocation. 525753dece8SMiguel Ojeda /// let mut v = mem::ManuallyDrop::new(v); 526753dece8SMiguel Ojeda /// 527753dece8SMiguel Ojeda /// // Pull out the various important pieces of information about `v` 528753dece8SMiguel Ojeda /// let p = v.as_mut_ptr(); 529753dece8SMiguel Ojeda /// let len = v.len(); 530753dece8SMiguel Ojeda /// let cap = v.capacity(); 531753dece8SMiguel Ojeda /// 532753dece8SMiguel Ojeda /// unsafe { 533753dece8SMiguel Ojeda /// // Overwrite memory with 4, 5, 6 534753dece8SMiguel Ojeda /// for i in 0..len as isize { 535753dece8SMiguel Ojeda /// ptr::write(p.offset(i), 4 + i); 536753dece8SMiguel Ojeda /// } 537753dece8SMiguel Ojeda /// 538753dece8SMiguel Ojeda /// // Put everything back together into a Vec 539753dece8SMiguel Ojeda /// let rebuilt = Vec::from_raw_parts(p, len, cap); 540753dece8SMiguel Ojeda /// assert_eq!(rebuilt, [4, 5, 6]); 541753dece8SMiguel Ojeda /// } 542753dece8SMiguel Ojeda /// ``` 543753dece8SMiguel Ojeda #[inline] 544753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 545753dece8SMiguel Ojeda pub unsafe fn from_raw_parts(ptr: *mut T, length: usize, capacity: usize) -> Self { 546753dece8SMiguel Ojeda unsafe { Self::from_raw_parts_in(ptr, length, capacity, Global) } 547753dece8SMiguel Ojeda } 548753dece8SMiguel Ojeda } 549753dece8SMiguel Ojeda 550753dece8SMiguel Ojeda impl<T, A: Allocator> Vec<T, A> { 551753dece8SMiguel Ojeda /// Constructs a new, empty `Vec<T, A>`. 552753dece8SMiguel Ojeda /// 553753dece8SMiguel Ojeda /// The vector will not allocate until elements are pushed onto it. 554753dece8SMiguel Ojeda /// 555753dece8SMiguel Ojeda /// # Examples 556753dece8SMiguel Ojeda /// 557753dece8SMiguel Ojeda /// ``` 558753dece8SMiguel Ojeda /// #![feature(allocator_api)] 559753dece8SMiguel Ojeda /// 560753dece8SMiguel Ojeda /// use std::alloc::System; 561753dece8SMiguel Ojeda /// 562753dece8SMiguel Ojeda /// # #[allow(unused_mut)] 563753dece8SMiguel Ojeda /// let mut vec: Vec<i32, _> = Vec::new_in(System); 564753dece8SMiguel Ojeda /// ``` 565753dece8SMiguel Ojeda #[inline] 566753dece8SMiguel Ojeda #[unstable(feature = "allocator_api", issue = "32838")] 567753dece8SMiguel Ojeda pub const fn new_in(alloc: A) -> Self { 568753dece8SMiguel Ojeda Vec { buf: RawVec::new_in(alloc), len: 0 } 569753dece8SMiguel Ojeda } 570753dece8SMiguel Ojeda 571753dece8SMiguel Ojeda /// Constructs a new, empty `Vec<T, A>` with the specified capacity with the provided 572753dece8SMiguel Ojeda /// allocator. 573753dece8SMiguel Ojeda /// 574753dece8SMiguel Ojeda /// The vector will be able to hold exactly `capacity` elements without 575753dece8SMiguel Ojeda /// reallocating. If `capacity` is 0, the vector will not allocate. 576753dece8SMiguel Ojeda /// 577753dece8SMiguel Ojeda /// It is important to note that although the returned vector has the 578753dece8SMiguel Ojeda /// *capacity* specified, the vector will have a zero *length*. For an 579753dece8SMiguel Ojeda /// explanation of the difference between length and capacity, see 580753dece8SMiguel Ojeda /// *[Capacity and reallocation]*. 581753dece8SMiguel Ojeda /// 582753dece8SMiguel Ojeda /// [Capacity and reallocation]: #capacity-and-reallocation 583753dece8SMiguel Ojeda /// 584753dece8SMiguel Ojeda /// # Panics 585753dece8SMiguel Ojeda /// 586753dece8SMiguel Ojeda /// Panics if the new capacity exceeds `isize::MAX` bytes. 587753dece8SMiguel Ojeda /// 588753dece8SMiguel Ojeda /// # Examples 589753dece8SMiguel Ojeda /// 590753dece8SMiguel Ojeda /// ``` 591753dece8SMiguel Ojeda /// #![feature(allocator_api)] 592753dece8SMiguel Ojeda /// 593753dece8SMiguel Ojeda /// use std::alloc::System; 594753dece8SMiguel Ojeda /// 595753dece8SMiguel Ojeda /// let mut vec = Vec::with_capacity_in(10, System); 596753dece8SMiguel Ojeda /// 597753dece8SMiguel Ojeda /// // The vector contains no items, even though it has capacity for more 598753dece8SMiguel Ojeda /// assert_eq!(vec.len(), 0); 599753dece8SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 600753dece8SMiguel Ojeda /// 601753dece8SMiguel Ojeda /// // These are all done without reallocating... 602753dece8SMiguel Ojeda /// for i in 0..10 { 603753dece8SMiguel Ojeda /// vec.push(i); 604753dece8SMiguel Ojeda /// } 605753dece8SMiguel Ojeda /// assert_eq!(vec.len(), 10); 606753dece8SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 607753dece8SMiguel Ojeda /// 608753dece8SMiguel Ojeda /// // ...but this may make the vector reallocate 609753dece8SMiguel Ojeda /// vec.push(11); 610753dece8SMiguel Ojeda /// assert_eq!(vec.len(), 11); 611753dece8SMiguel Ojeda /// assert!(vec.capacity() >= 11); 612753dece8SMiguel Ojeda /// ``` 613753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 614753dece8SMiguel Ojeda #[inline] 615753dece8SMiguel Ojeda #[unstable(feature = "allocator_api", issue = "32838")] 616753dece8SMiguel Ojeda pub fn with_capacity_in(capacity: usize, alloc: A) -> Self { 617753dece8SMiguel Ojeda Vec { buf: RawVec::with_capacity_in(capacity, alloc), len: 0 } 618753dece8SMiguel Ojeda } 619753dece8SMiguel Ojeda 620753dece8SMiguel Ojeda /// Creates a `Vec<T, A>` directly from the raw components of another vector. 621753dece8SMiguel Ojeda /// 622753dece8SMiguel Ojeda /// # Safety 623753dece8SMiguel Ojeda /// 624753dece8SMiguel Ojeda /// This is highly unsafe, due to the number of invariants that aren't 625753dece8SMiguel Ojeda /// checked: 626753dece8SMiguel Ojeda /// 627753dece8SMiguel Ojeda /// * `ptr` needs to have been previously allocated via [`String`]/`Vec<T>` 628753dece8SMiguel Ojeda /// (at least, it's highly likely to be incorrect if it wasn't). 629753dece8SMiguel Ojeda /// * `T` needs to have the same size and alignment as what `ptr` was allocated with. 630753dece8SMiguel Ojeda /// (`T` having a less strict alignment is not sufficient, the alignment really 631753dece8SMiguel Ojeda /// needs to be equal to satisfy the [`dealloc`] requirement that memory must be 632753dece8SMiguel Ojeda /// allocated and deallocated with the same layout.) 633753dece8SMiguel Ojeda /// * `length` needs to be less than or equal to `capacity`. 634753dece8SMiguel Ojeda /// * `capacity` needs to be the capacity that the pointer was allocated with. 635753dece8SMiguel Ojeda /// 636753dece8SMiguel Ojeda /// Violating these may cause problems like corrupting the allocator's 637753dece8SMiguel Ojeda /// internal data structures. For example it is **not** safe 638753dece8SMiguel Ojeda /// to build a `Vec<u8>` from a pointer to a C `char` array with length `size_t`. 639753dece8SMiguel Ojeda /// It's also not safe to build one from a `Vec<u16>` and its length, because 640753dece8SMiguel Ojeda /// the allocator cares about the alignment, and these two types have different 641753dece8SMiguel Ojeda /// alignments. The buffer was allocated with alignment 2 (for `u16`), but after 642753dece8SMiguel Ojeda /// turning it into a `Vec<u8>` it'll be deallocated with alignment 1. 643753dece8SMiguel Ojeda /// 644753dece8SMiguel Ojeda /// The ownership of `ptr` is effectively transferred to the 645753dece8SMiguel Ojeda /// `Vec<T>` which may then deallocate, reallocate or change the 646753dece8SMiguel Ojeda /// contents of memory pointed to by the pointer at will. Ensure 647753dece8SMiguel Ojeda /// that nothing else uses the pointer after calling this 648753dece8SMiguel Ojeda /// function. 649753dece8SMiguel Ojeda /// 650753dece8SMiguel Ojeda /// [`String`]: crate::string::String 651753dece8SMiguel Ojeda /// [`dealloc`]: crate::alloc::GlobalAlloc::dealloc 652753dece8SMiguel Ojeda /// 653753dece8SMiguel Ojeda /// # Examples 654753dece8SMiguel Ojeda /// 655753dece8SMiguel Ojeda /// ``` 656753dece8SMiguel Ojeda /// #![feature(allocator_api)] 657753dece8SMiguel Ojeda /// 658753dece8SMiguel Ojeda /// use std::alloc::System; 659753dece8SMiguel Ojeda /// 660753dece8SMiguel Ojeda /// use std::ptr; 661753dece8SMiguel Ojeda /// use std::mem; 662753dece8SMiguel Ojeda /// 663753dece8SMiguel Ojeda /// let mut v = Vec::with_capacity_in(3, System); 664753dece8SMiguel Ojeda /// v.push(1); 665753dece8SMiguel Ojeda /// v.push(2); 666753dece8SMiguel Ojeda /// v.push(3); 667753dece8SMiguel Ojeda /// 668753dece8SMiguel Ojeda // FIXME Update this when vec_into_raw_parts is stabilized 669753dece8SMiguel Ojeda /// // Prevent running `v`'s destructor so we are in complete control 670753dece8SMiguel Ojeda /// // of the allocation. 671753dece8SMiguel Ojeda /// let mut v = mem::ManuallyDrop::new(v); 672753dece8SMiguel Ojeda /// 673753dece8SMiguel Ojeda /// // Pull out the various important pieces of information about `v` 674753dece8SMiguel Ojeda /// let p = v.as_mut_ptr(); 675753dece8SMiguel Ojeda /// let len = v.len(); 676753dece8SMiguel Ojeda /// let cap = v.capacity(); 677753dece8SMiguel Ojeda /// let alloc = v.allocator(); 678753dece8SMiguel Ojeda /// 679753dece8SMiguel Ojeda /// unsafe { 680753dece8SMiguel Ojeda /// // Overwrite memory with 4, 5, 6 681753dece8SMiguel Ojeda /// for i in 0..len as isize { 682753dece8SMiguel Ojeda /// ptr::write(p.offset(i), 4 + i); 683753dece8SMiguel Ojeda /// } 684753dece8SMiguel Ojeda /// 685753dece8SMiguel Ojeda /// // Put everything back together into a Vec 686753dece8SMiguel Ojeda /// let rebuilt = Vec::from_raw_parts_in(p, len, cap, alloc.clone()); 687753dece8SMiguel Ojeda /// assert_eq!(rebuilt, [4, 5, 6]); 688753dece8SMiguel Ojeda /// } 689753dece8SMiguel Ojeda /// ``` 690753dece8SMiguel Ojeda #[inline] 691753dece8SMiguel Ojeda #[unstable(feature = "allocator_api", issue = "32838")] 692753dece8SMiguel Ojeda pub unsafe fn from_raw_parts_in(ptr: *mut T, length: usize, capacity: usize, alloc: A) -> Self { 693753dece8SMiguel Ojeda unsafe { Vec { buf: RawVec::from_raw_parts_in(ptr, capacity, alloc), len: length } } 694753dece8SMiguel Ojeda } 695753dece8SMiguel Ojeda 696753dece8SMiguel Ojeda /// Decomposes a `Vec<T>` into its raw components. 697753dece8SMiguel Ojeda /// 698753dece8SMiguel Ojeda /// Returns the raw pointer to the underlying data, the length of 699753dece8SMiguel Ojeda /// the vector (in elements), and the allocated capacity of the 700753dece8SMiguel Ojeda /// data (in elements). These are the same arguments in the same 701753dece8SMiguel Ojeda /// order as the arguments to [`from_raw_parts`]. 702753dece8SMiguel Ojeda /// 703753dece8SMiguel Ojeda /// After calling this function, the caller is responsible for the 704753dece8SMiguel Ojeda /// memory previously managed by the `Vec`. The only way to do 705753dece8SMiguel Ojeda /// this is to convert the raw pointer, length, and capacity back 706753dece8SMiguel Ojeda /// into a `Vec` with the [`from_raw_parts`] function, allowing 707753dece8SMiguel Ojeda /// the destructor to perform the cleanup. 708753dece8SMiguel Ojeda /// 709753dece8SMiguel Ojeda /// [`from_raw_parts`]: Vec::from_raw_parts 710753dece8SMiguel Ojeda /// 711753dece8SMiguel Ojeda /// # Examples 712753dece8SMiguel Ojeda /// 713753dece8SMiguel Ojeda /// ``` 714753dece8SMiguel Ojeda /// #![feature(vec_into_raw_parts)] 715753dece8SMiguel Ojeda /// let v: Vec<i32> = vec![-1, 0, 1]; 716753dece8SMiguel Ojeda /// 717753dece8SMiguel Ojeda /// let (ptr, len, cap) = v.into_raw_parts(); 718753dece8SMiguel Ojeda /// 719753dece8SMiguel Ojeda /// let rebuilt = unsafe { 720753dece8SMiguel Ojeda /// // We can now make changes to the components, such as 721753dece8SMiguel Ojeda /// // transmuting the raw pointer to a compatible type. 722753dece8SMiguel Ojeda /// let ptr = ptr as *mut u32; 723753dece8SMiguel Ojeda /// 724753dece8SMiguel Ojeda /// Vec::from_raw_parts(ptr, len, cap) 725753dece8SMiguel Ojeda /// }; 726753dece8SMiguel Ojeda /// assert_eq!(rebuilt, [4294967295, 0, 1]); 727753dece8SMiguel Ojeda /// ``` 728753dece8SMiguel Ojeda #[unstable(feature = "vec_into_raw_parts", reason = "new API", issue = "65816")] 729753dece8SMiguel Ojeda pub fn into_raw_parts(self) -> (*mut T, usize, usize) { 730753dece8SMiguel Ojeda let mut me = ManuallyDrop::new(self); 731753dece8SMiguel Ojeda (me.as_mut_ptr(), me.len(), me.capacity()) 732753dece8SMiguel Ojeda } 733753dece8SMiguel Ojeda 734753dece8SMiguel Ojeda /// Decomposes a `Vec<T>` into its raw components. 735753dece8SMiguel Ojeda /// 736753dece8SMiguel Ojeda /// Returns the raw pointer to the underlying data, the length of the vector (in elements), 737753dece8SMiguel Ojeda /// the allocated capacity of the data (in elements), and the allocator. These are the same 738753dece8SMiguel Ojeda /// arguments in the same order as the arguments to [`from_raw_parts_in`]. 739753dece8SMiguel Ojeda /// 740753dece8SMiguel Ojeda /// After calling this function, the caller is responsible for the 741753dece8SMiguel Ojeda /// memory previously managed by the `Vec`. The only way to do 742753dece8SMiguel Ojeda /// this is to convert the raw pointer, length, and capacity back 743753dece8SMiguel Ojeda /// into a `Vec` with the [`from_raw_parts_in`] function, allowing 744753dece8SMiguel Ojeda /// the destructor to perform the cleanup. 745753dece8SMiguel Ojeda /// 746753dece8SMiguel Ojeda /// [`from_raw_parts_in`]: Vec::from_raw_parts_in 747753dece8SMiguel Ojeda /// 748753dece8SMiguel Ojeda /// # Examples 749753dece8SMiguel Ojeda /// 750753dece8SMiguel Ojeda /// ``` 751753dece8SMiguel Ojeda /// #![feature(allocator_api, vec_into_raw_parts)] 752753dece8SMiguel Ojeda /// 753753dece8SMiguel Ojeda /// use std::alloc::System; 754753dece8SMiguel Ojeda /// 755753dece8SMiguel Ojeda /// let mut v: Vec<i32, System> = Vec::new_in(System); 756753dece8SMiguel Ojeda /// v.push(-1); 757753dece8SMiguel Ojeda /// v.push(0); 758753dece8SMiguel Ojeda /// v.push(1); 759753dece8SMiguel Ojeda /// 760753dece8SMiguel Ojeda /// let (ptr, len, cap, alloc) = v.into_raw_parts_with_alloc(); 761753dece8SMiguel Ojeda /// 762753dece8SMiguel Ojeda /// let rebuilt = unsafe { 763753dece8SMiguel Ojeda /// // We can now make changes to the components, such as 764753dece8SMiguel Ojeda /// // transmuting the raw pointer to a compatible type. 765753dece8SMiguel Ojeda /// let ptr = ptr as *mut u32; 766753dece8SMiguel Ojeda /// 767753dece8SMiguel Ojeda /// Vec::from_raw_parts_in(ptr, len, cap, alloc) 768753dece8SMiguel Ojeda /// }; 769753dece8SMiguel Ojeda /// assert_eq!(rebuilt, [4294967295, 0, 1]); 770753dece8SMiguel Ojeda /// ``` 771753dece8SMiguel Ojeda #[unstable(feature = "allocator_api", issue = "32838")] 772753dece8SMiguel Ojeda // #[unstable(feature = "vec_into_raw_parts", reason = "new API", issue = "65816")] 773753dece8SMiguel Ojeda pub fn into_raw_parts_with_alloc(self) -> (*mut T, usize, usize, A) { 774753dece8SMiguel Ojeda let mut me = ManuallyDrop::new(self); 775753dece8SMiguel Ojeda let len = me.len(); 776753dece8SMiguel Ojeda let capacity = me.capacity(); 777753dece8SMiguel Ojeda let ptr = me.as_mut_ptr(); 778753dece8SMiguel Ojeda let alloc = unsafe { ptr::read(me.allocator()) }; 779753dece8SMiguel Ojeda (ptr, len, capacity, alloc) 780753dece8SMiguel Ojeda } 781753dece8SMiguel Ojeda 782753dece8SMiguel Ojeda /// Returns the number of elements the vector can hold without 783753dece8SMiguel Ojeda /// reallocating. 784753dece8SMiguel Ojeda /// 785753dece8SMiguel Ojeda /// # Examples 786753dece8SMiguel Ojeda /// 787753dece8SMiguel Ojeda /// ``` 788753dece8SMiguel Ojeda /// let vec: Vec<i32> = Vec::with_capacity(10); 789753dece8SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 790753dece8SMiguel Ojeda /// ``` 791753dece8SMiguel Ojeda #[inline] 792753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 793753dece8SMiguel Ojeda pub fn capacity(&self) -> usize { 794753dece8SMiguel Ojeda self.buf.capacity() 795753dece8SMiguel Ojeda } 796753dece8SMiguel Ojeda 797753dece8SMiguel Ojeda /// Reserves capacity for at least `additional` more elements to be inserted 798753dece8SMiguel Ojeda /// in the given `Vec<T>`. The collection may reserve more space to avoid 799753dece8SMiguel Ojeda /// frequent reallocations. After calling `reserve`, capacity will be 800753dece8SMiguel Ojeda /// greater than or equal to `self.len() + additional`. Does nothing if 801753dece8SMiguel Ojeda /// capacity is already sufficient. 802753dece8SMiguel Ojeda /// 803753dece8SMiguel Ojeda /// # Panics 804753dece8SMiguel Ojeda /// 805753dece8SMiguel Ojeda /// Panics if the new capacity exceeds `isize::MAX` bytes. 806753dece8SMiguel Ojeda /// 807753dece8SMiguel Ojeda /// # Examples 808753dece8SMiguel Ojeda /// 809753dece8SMiguel Ojeda /// ``` 810753dece8SMiguel Ojeda /// let mut vec = vec![1]; 811753dece8SMiguel Ojeda /// vec.reserve(10); 812753dece8SMiguel Ojeda /// assert!(vec.capacity() >= 11); 813753dece8SMiguel Ojeda /// ``` 814753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 815753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 816753dece8SMiguel Ojeda pub fn reserve(&mut self, additional: usize) { 817753dece8SMiguel Ojeda self.buf.reserve(self.len, additional); 818753dece8SMiguel Ojeda } 819753dece8SMiguel Ojeda 820753dece8SMiguel Ojeda /// Reserves the minimum capacity for exactly `additional` more elements to 821753dece8SMiguel Ojeda /// be inserted in the given `Vec<T>`. After calling `reserve_exact`, 822753dece8SMiguel Ojeda /// capacity will be greater than or equal to `self.len() + additional`. 823753dece8SMiguel Ojeda /// Does nothing if the capacity is already sufficient. 824753dece8SMiguel Ojeda /// 825753dece8SMiguel Ojeda /// Note that the allocator may give the collection more space than it 826753dece8SMiguel Ojeda /// requests. Therefore, capacity can not be relied upon to be precisely 827753dece8SMiguel Ojeda /// minimal. Prefer [`reserve`] if future insertions are expected. 828753dece8SMiguel Ojeda /// 829753dece8SMiguel Ojeda /// [`reserve`]: Vec::reserve 830753dece8SMiguel Ojeda /// 831753dece8SMiguel Ojeda /// # Panics 832753dece8SMiguel Ojeda /// 833753dece8SMiguel Ojeda /// Panics if the new capacity exceeds `isize::MAX` bytes. 834753dece8SMiguel Ojeda /// 835753dece8SMiguel Ojeda /// # Examples 836753dece8SMiguel Ojeda /// 837753dece8SMiguel Ojeda /// ``` 838753dece8SMiguel Ojeda /// let mut vec = vec![1]; 839753dece8SMiguel Ojeda /// vec.reserve_exact(10); 840753dece8SMiguel Ojeda /// assert!(vec.capacity() >= 11); 841753dece8SMiguel Ojeda /// ``` 842753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 843753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 844753dece8SMiguel Ojeda pub fn reserve_exact(&mut self, additional: usize) { 845753dece8SMiguel Ojeda self.buf.reserve_exact(self.len, additional); 846753dece8SMiguel Ojeda } 847753dece8SMiguel Ojeda 848753dece8SMiguel Ojeda /// Tries to reserve capacity for at least `additional` more elements to be inserted 849753dece8SMiguel Ojeda /// in the given `Vec<T>`. The collection may reserve more space to avoid 850753dece8SMiguel Ojeda /// frequent reallocations. After calling `try_reserve`, capacity will be 851753dece8SMiguel Ojeda /// greater than or equal to `self.len() + additional`. Does nothing if 852753dece8SMiguel Ojeda /// capacity is already sufficient. 853753dece8SMiguel Ojeda /// 854753dece8SMiguel Ojeda /// # Errors 855753dece8SMiguel Ojeda /// 856753dece8SMiguel Ojeda /// If the capacity overflows, or the allocator reports a failure, then an error 857753dece8SMiguel Ojeda /// is returned. 858753dece8SMiguel Ojeda /// 859753dece8SMiguel Ojeda /// # Examples 860753dece8SMiguel Ojeda /// 861753dece8SMiguel Ojeda /// ``` 862753dece8SMiguel Ojeda /// use std::collections::TryReserveError; 863753dece8SMiguel Ojeda /// 864753dece8SMiguel Ojeda /// fn process_data(data: &[u32]) -> Result<Vec<u32>, TryReserveError> { 865753dece8SMiguel Ojeda /// let mut output = Vec::new(); 866753dece8SMiguel Ojeda /// 867753dece8SMiguel Ojeda /// // Pre-reserve the memory, exiting if we can't 868753dece8SMiguel Ojeda /// output.try_reserve(data.len())?; 869753dece8SMiguel Ojeda /// 870753dece8SMiguel Ojeda /// // Now we know this can't OOM in the middle of our complex work 871753dece8SMiguel Ojeda /// output.extend(data.iter().map(|&val| { 872753dece8SMiguel Ojeda /// val * 2 + 5 // very complicated 873753dece8SMiguel Ojeda /// })); 874753dece8SMiguel Ojeda /// 875753dece8SMiguel Ojeda /// Ok(output) 876753dece8SMiguel Ojeda /// } 877753dece8SMiguel Ojeda /// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?"); 878753dece8SMiguel Ojeda /// ``` 879753dece8SMiguel Ojeda #[stable(feature = "try_reserve", since = "1.57.0")] 880753dece8SMiguel Ojeda pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> { 881753dece8SMiguel Ojeda self.buf.try_reserve(self.len, additional) 882753dece8SMiguel Ojeda } 883753dece8SMiguel Ojeda 884753dece8SMiguel Ojeda /// Tries to reserve the minimum capacity for exactly `additional` 885753dece8SMiguel Ojeda /// elements to be inserted in the given `Vec<T>`. After calling 886753dece8SMiguel Ojeda /// `try_reserve_exact`, capacity will be greater than or equal to 887753dece8SMiguel Ojeda /// `self.len() + additional` if it returns `Ok(())`. 888753dece8SMiguel Ojeda /// Does nothing if the capacity is already sufficient. 889753dece8SMiguel Ojeda /// 890753dece8SMiguel Ojeda /// Note that the allocator may give the collection more space than it 891753dece8SMiguel Ojeda /// requests. Therefore, capacity can not be relied upon to be precisely 892753dece8SMiguel Ojeda /// minimal. Prefer [`try_reserve`] if future insertions are expected. 893753dece8SMiguel Ojeda /// 894753dece8SMiguel Ojeda /// [`try_reserve`]: Vec::try_reserve 895753dece8SMiguel Ojeda /// 896753dece8SMiguel Ojeda /// # Errors 897753dece8SMiguel Ojeda /// 898753dece8SMiguel Ojeda /// If the capacity overflows, or the allocator reports a failure, then an error 899753dece8SMiguel Ojeda /// is returned. 900753dece8SMiguel Ojeda /// 901753dece8SMiguel Ojeda /// # Examples 902753dece8SMiguel Ojeda /// 903753dece8SMiguel Ojeda /// ``` 904753dece8SMiguel Ojeda /// use std::collections::TryReserveError; 905753dece8SMiguel Ojeda /// 906753dece8SMiguel Ojeda /// fn process_data(data: &[u32]) -> Result<Vec<u32>, TryReserveError> { 907753dece8SMiguel Ojeda /// let mut output = Vec::new(); 908753dece8SMiguel Ojeda /// 909753dece8SMiguel Ojeda /// // Pre-reserve the memory, exiting if we can't 910753dece8SMiguel Ojeda /// output.try_reserve_exact(data.len())?; 911753dece8SMiguel Ojeda /// 912753dece8SMiguel Ojeda /// // Now we know this can't OOM in the middle of our complex work 913753dece8SMiguel Ojeda /// output.extend(data.iter().map(|&val| { 914753dece8SMiguel Ojeda /// val * 2 + 5 // very complicated 915753dece8SMiguel Ojeda /// })); 916753dece8SMiguel Ojeda /// 917753dece8SMiguel Ojeda /// Ok(output) 918753dece8SMiguel Ojeda /// } 919753dece8SMiguel Ojeda /// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?"); 920753dece8SMiguel Ojeda /// ``` 921753dece8SMiguel Ojeda #[stable(feature = "try_reserve", since = "1.57.0")] 922753dece8SMiguel Ojeda pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> { 923753dece8SMiguel Ojeda self.buf.try_reserve_exact(self.len, additional) 924753dece8SMiguel Ojeda } 925753dece8SMiguel Ojeda 926753dece8SMiguel Ojeda /// Shrinks the capacity of the vector as much as possible. 927753dece8SMiguel Ojeda /// 928753dece8SMiguel Ojeda /// It will drop down as close as possible to the length but the allocator 929753dece8SMiguel Ojeda /// may still inform the vector that there is space for a few more elements. 930753dece8SMiguel Ojeda /// 931753dece8SMiguel Ojeda /// # Examples 932753dece8SMiguel Ojeda /// 933753dece8SMiguel Ojeda /// ``` 934753dece8SMiguel Ojeda /// let mut vec = Vec::with_capacity(10); 935753dece8SMiguel Ojeda /// vec.extend([1, 2, 3]); 936753dece8SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 937753dece8SMiguel Ojeda /// vec.shrink_to_fit(); 938753dece8SMiguel Ojeda /// assert!(vec.capacity() >= 3); 939753dece8SMiguel Ojeda /// ``` 940753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 941753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 942753dece8SMiguel Ojeda pub fn shrink_to_fit(&mut self) { 943753dece8SMiguel Ojeda // The capacity is never less than the length, and there's nothing to do when 944753dece8SMiguel Ojeda // they are equal, so we can avoid the panic case in `RawVec::shrink_to_fit` 945753dece8SMiguel Ojeda // by only calling it with a greater capacity. 946753dece8SMiguel Ojeda if self.capacity() > self.len { 947753dece8SMiguel Ojeda self.buf.shrink_to_fit(self.len); 948753dece8SMiguel Ojeda } 949753dece8SMiguel Ojeda } 950753dece8SMiguel Ojeda 951753dece8SMiguel Ojeda /// Shrinks the capacity of the vector with a lower bound. 952753dece8SMiguel Ojeda /// 953753dece8SMiguel Ojeda /// The capacity will remain at least as large as both the length 954753dece8SMiguel Ojeda /// and the supplied value. 955753dece8SMiguel Ojeda /// 956753dece8SMiguel Ojeda /// If the current capacity is less than the lower limit, this is a no-op. 957753dece8SMiguel Ojeda /// 958753dece8SMiguel Ojeda /// # Examples 959753dece8SMiguel Ojeda /// 960753dece8SMiguel Ojeda /// ``` 961753dece8SMiguel Ojeda /// let mut vec = Vec::with_capacity(10); 962753dece8SMiguel Ojeda /// vec.extend([1, 2, 3]); 963753dece8SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 964753dece8SMiguel Ojeda /// vec.shrink_to(4); 965753dece8SMiguel Ojeda /// assert!(vec.capacity() >= 4); 966753dece8SMiguel Ojeda /// vec.shrink_to(0); 967753dece8SMiguel Ojeda /// assert!(vec.capacity() >= 3); 968753dece8SMiguel Ojeda /// ``` 969753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 970753dece8SMiguel Ojeda #[stable(feature = "shrink_to", since = "1.56.0")] 971753dece8SMiguel Ojeda pub fn shrink_to(&mut self, min_capacity: usize) { 972753dece8SMiguel Ojeda if self.capacity() > min_capacity { 973753dece8SMiguel Ojeda self.buf.shrink_to_fit(cmp::max(self.len, min_capacity)); 974753dece8SMiguel Ojeda } 975753dece8SMiguel Ojeda } 976753dece8SMiguel Ojeda 977753dece8SMiguel Ojeda /// Converts the vector into [`Box<[T]>`][owned slice]. 978753dece8SMiguel Ojeda /// 979753dece8SMiguel Ojeda /// Note that this will drop any excess capacity. 980753dece8SMiguel Ojeda /// 981753dece8SMiguel Ojeda /// [owned slice]: Box 982753dece8SMiguel Ojeda /// 983753dece8SMiguel Ojeda /// # Examples 984753dece8SMiguel Ojeda /// 985753dece8SMiguel Ojeda /// ``` 986753dece8SMiguel Ojeda /// let v = vec![1, 2, 3]; 987753dece8SMiguel Ojeda /// 988753dece8SMiguel Ojeda /// let slice = v.into_boxed_slice(); 989753dece8SMiguel Ojeda /// ``` 990753dece8SMiguel Ojeda /// 991753dece8SMiguel Ojeda /// Any excess capacity is removed: 992753dece8SMiguel Ojeda /// 993753dece8SMiguel Ojeda /// ``` 994753dece8SMiguel Ojeda /// let mut vec = Vec::with_capacity(10); 995753dece8SMiguel Ojeda /// vec.extend([1, 2, 3]); 996753dece8SMiguel Ojeda /// 997753dece8SMiguel Ojeda /// assert_eq!(vec.capacity(), 10); 998753dece8SMiguel Ojeda /// let slice = vec.into_boxed_slice(); 999753dece8SMiguel Ojeda /// assert_eq!(slice.into_vec().capacity(), 3); 1000753dece8SMiguel Ojeda /// ``` 1001753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 1002753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1003753dece8SMiguel Ojeda pub fn into_boxed_slice(mut self) -> Box<[T], A> { 1004753dece8SMiguel Ojeda unsafe { 1005753dece8SMiguel Ojeda self.shrink_to_fit(); 1006753dece8SMiguel Ojeda let me = ManuallyDrop::new(self); 1007753dece8SMiguel Ojeda let buf = ptr::read(&me.buf); 1008753dece8SMiguel Ojeda let len = me.len(); 1009753dece8SMiguel Ojeda buf.into_box(len).assume_init() 1010753dece8SMiguel Ojeda } 1011753dece8SMiguel Ojeda } 1012753dece8SMiguel Ojeda 1013753dece8SMiguel Ojeda /// Shortens the vector, keeping the first `len` elements and dropping 1014753dece8SMiguel Ojeda /// the rest. 1015753dece8SMiguel Ojeda /// 1016753dece8SMiguel Ojeda /// If `len` is greater than the vector's current length, this has no 1017753dece8SMiguel Ojeda /// effect. 1018753dece8SMiguel Ojeda /// 1019753dece8SMiguel Ojeda /// The [`drain`] method can emulate `truncate`, but causes the excess 1020753dece8SMiguel Ojeda /// elements to be returned instead of dropped. 1021753dece8SMiguel Ojeda /// 1022753dece8SMiguel Ojeda /// Note that this method has no effect on the allocated capacity 1023753dece8SMiguel Ojeda /// of the vector. 1024753dece8SMiguel Ojeda /// 1025753dece8SMiguel Ojeda /// # Examples 1026753dece8SMiguel Ojeda /// 1027753dece8SMiguel Ojeda /// Truncating a five element vector to two elements: 1028753dece8SMiguel Ojeda /// 1029753dece8SMiguel Ojeda /// ``` 1030753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3, 4, 5]; 1031753dece8SMiguel Ojeda /// vec.truncate(2); 1032753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2]); 1033753dece8SMiguel Ojeda /// ``` 1034753dece8SMiguel Ojeda /// 1035753dece8SMiguel Ojeda /// No truncation occurs when `len` is greater than the vector's current 1036753dece8SMiguel Ojeda /// length: 1037753dece8SMiguel Ojeda /// 1038753dece8SMiguel Ojeda /// ``` 1039753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3]; 1040753dece8SMiguel Ojeda /// vec.truncate(8); 1041753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2, 3]); 1042753dece8SMiguel Ojeda /// ``` 1043753dece8SMiguel Ojeda /// 1044753dece8SMiguel Ojeda /// Truncating when `len == 0` is equivalent to calling the [`clear`] 1045753dece8SMiguel Ojeda /// method. 1046753dece8SMiguel Ojeda /// 1047753dece8SMiguel Ojeda /// ``` 1048753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3]; 1049753dece8SMiguel Ojeda /// vec.truncate(0); 1050753dece8SMiguel Ojeda /// assert_eq!(vec, []); 1051753dece8SMiguel Ojeda /// ``` 1052753dece8SMiguel Ojeda /// 1053753dece8SMiguel Ojeda /// [`clear`]: Vec::clear 1054753dece8SMiguel Ojeda /// [`drain`]: Vec::drain 1055753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1056753dece8SMiguel Ojeda pub fn truncate(&mut self, len: usize) { 1057753dece8SMiguel Ojeda // This is safe because: 1058753dece8SMiguel Ojeda // 1059753dece8SMiguel Ojeda // * the slice passed to `drop_in_place` is valid; the `len > self.len` 1060753dece8SMiguel Ojeda // case avoids creating an invalid slice, and 1061753dece8SMiguel Ojeda // * the `len` of the vector is shrunk before calling `drop_in_place`, 1062753dece8SMiguel Ojeda // such that no value will be dropped twice in case `drop_in_place` 1063753dece8SMiguel Ojeda // were to panic once (if it panics twice, the program aborts). 1064753dece8SMiguel Ojeda unsafe { 1065753dece8SMiguel Ojeda // Note: It's intentional that this is `>` and not `>=`. 1066753dece8SMiguel Ojeda // Changing it to `>=` has negative performance 1067753dece8SMiguel Ojeda // implications in some cases. See #78884 for more. 1068753dece8SMiguel Ojeda if len > self.len { 1069753dece8SMiguel Ojeda return; 1070753dece8SMiguel Ojeda } 1071753dece8SMiguel Ojeda let remaining_len = self.len - len; 1072753dece8SMiguel Ojeda let s = ptr::slice_from_raw_parts_mut(self.as_mut_ptr().add(len), remaining_len); 1073753dece8SMiguel Ojeda self.len = len; 1074753dece8SMiguel Ojeda ptr::drop_in_place(s); 1075753dece8SMiguel Ojeda } 1076753dece8SMiguel Ojeda } 1077753dece8SMiguel Ojeda 1078753dece8SMiguel Ojeda /// Extracts a slice containing the entire vector. 1079753dece8SMiguel Ojeda /// 1080753dece8SMiguel Ojeda /// Equivalent to `&s[..]`. 1081753dece8SMiguel Ojeda /// 1082753dece8SMiguel Ojeda /// # Examples 1083753dece8SMiguel Ojeda /// 1084753dece8SMiguel Ojeda /// ``` 1085753dece8SMiguel Ojeda /// use std::io::{self, Write}; 1086753dece8SMiguel Ojeda /// let buffer = vec![1, 2, 3, 5, 8]; 1087753dece8SMiguel Ojeda /// io::sink().write(buffer.as_slice()).unwrap(); 1088753dece8SMiguel Ojeda /// ``` 1089753dece8SMiguel Ojeda #[inline] 1090753dece8SMiguel Ojeda #[stable(feature = "vec_as_slice", since = "1.7.0")] 1091753dece8SMiguel Ojeda pub fn as_slice(&self) -> &[T] { 1092753dece8SMiguel Ojeda self 1093753dece8SMiguel Ojeda } 1094753dece8SMiguel Ojeda 1095753dece8SMiguel Ojeda /// Extracts a mutable slice of the entire vector. 1096753dece8SMiguel Ojeda /// 1097753dece8SMiguel Ojeda /// Equivalent to `&mut s[..]`. 1098753dece8SMiguel Ojeda /// 1099753dece8SMiguel Ojeda /// # Examples 1100753dece8SMiguel Ojeda /// 1101753dece8SMiguel Ojeda /// ``` 1102753dece8SMiguel Ojeda /// use std::io::{self, Read}; 1103753dece8SMiguel Ojeda /// let mut buffer = vec![0; 3]; 1104753dece8SMiguel Ojeda /// io::repeat(0b101).read_exact(buffer.as_mut_slice()).unwrap(); 1105753dece8SMiguel Ojeda /// ``` 1106753dece8SMiguel Ojeda #[inline] 1107753dece8SMiguel Ojeda #[stable(feature = "vec_as_slice", since = "1.7.0")] 1108753dece8SMiguel Ojeda pub fn as_mut_slice(&mut self) -> &mut [T] { 1109753dece8SMiguel Ojeda self 1110753dece8SMiguel Ojeda } 1111753dece8SMiguel Ojeda 1112753dece8SMiguel Ojeda /// Returns a raw pointer to the vector's buffer. 1113753dece8SMiguel Ojeda /// 1114753dece8SMiguel Ojeda /// The caller must ensure that the vector outlives the pointer this 1115753dece8SMiguel Ojeda /// function returns, or else it will end up pointing to garbage. 1116753dece8SMiguel Ojeda /// Modifying the vector may cause its buffer to be reallocated, 1117753dece8SMiguel Ojeda /// which would also make any pointers to it invalid. 1118753dece8SMiguel Ojeda /// 1119753dece8SMiguel Ojeda /// The caller must also ensure that the memory the pointer (non-transitively) points to 1120753dece8SMiguel Ojeda /// is never written to (except inside an `UnsafeCell`) using this pointer or any pointer 1121753dece8SMiguel Ojeda /// derived from it. If you need to mutate the contents of the slice, use [`as_mut_ptr`]. 1122753dece8SMiguel Ojeda /// 1123753dece8SMiguel Ojeda /// # Examples 1124753dece8SMiguel Ojeda /// 1125753dece8SMiguel Ojeda /// ``` 1126753dece8SMiguel Ojeda /// let x = vec![1, 2, 4]; 1127753dece8SMiguel Ojeda /// let x_ptr = x.as_ptr(); 1128753dece8SMiguel Ojeda /// 1129753dece8SMiguel Ojeda /// unsafe { 1130753dece8SMiguel Ojeda /// for i in 0..x.len() { 1131753dece8SMiguel Ojeda /// assert_eq!(*x_ptr.add(i), 1 << i); 1132753dece8SMiguel Ojeda /// } 1133753dece8SMiguel Ojeda /// } 1134753dece8SMiguel Ojeda /// ``` 1135753dece8SMiguel Ojeda /// 1136753dece8SMiguel Ojeda /// [`as_mut_ptr`]: Vec::as_mut_ptr 1137753dece8SMiguel Ojeda #[stable(feature = "vec_as_ptr", since = "1.37.0")] 1138753dece8SMiguel Ojeda #[inline] 1139753dece8SMiguel Ojeda pub fn as_ptr(&self) -> *const T { 1140753dece8SMiguel Ojeda // We shadow the slice method of the same name to avoid going through 1141753dece8SMiguel Ojeda // `deref`, which creates an intermediate reference. 1142753dece8SMiguel Ojeda let ptr = self.buf.ptr(); 1143753dece8SMiguel Ojeda unsafe { 1144753dece8SMiguel Ojeda assume(!ptr.is_null()); 1145753dece8SMiguel Ojeda } 1146753dece8SMiguel Ojeda ptr 1147753dece8SMiguel Ojeda } 1148753dece8SMiguel Ojeda 1149753dece8SMiguel Ojeda /// Returns an unsafe mutable pointer to the vector's buffer. 1150753dece8SMiguel Ojeda /// 1151753dece8SMiguel Ojeda /// The caller must ensure that the vector outlives the pointer this 1152753dece8SMiguel Ojeda /// function returns, or else it will end up pointing to garbage. 1153753dece8SMiguel Ojeda /// Modifying the vector may cause its buffer to be reallocated, 1154753dece8SMiguel Ojeda /// which would also make any pointers to it invalid. 1155753dece8SMiguel Ojeda /// 1156753dece8SMiguel Ojeda /// # Examples 1157753dece8SMiguel Ojeda /// 1158753dece8SMiguel Ojeda /// ``` 1159753dece8SMiguel Ojeda /// // Allocate vector big enough for 4 elements. 1160753dece8SMiguel Ojeda /// let size = 4; 1161753dece8SMiguel Ojeda /// let mut x: Vec<i32> = Vec::with_capacity(size); 1162753dece8SMiguel Ojeda /// let x_ptr = x.as_mut_ptr(); 1163753dece8SMiguel Ojeda /// 1164753dece8SMiguel Ojeda /// // Initialize elements via raw pointer writes, then set length. 1165753dece8SMiguel Ojeda /// unsafe { 1166753dece8SMiguel Ojeda /// for i in 0..size { 1167753dece8SMiguel Ojeda /// *x_ptr.add(i) = i as i32; 1168753dece8SMiguel Ojeda /// } 1169753dece8SMiguel Ojeda /// x.set_len(size); 1170753dece8SMiguel Ojeda /// } 1171753dece8SMiguel Ojeda /// assert_eq!(&*x, &[0, 1, 2, 3]); 1172753dece8SMiguel Ojeda /// ``` 1173753dece8SMiguel Ojeda #[stable(feature = "vec_as_ptr", since = "1.37.0")] 1174753dece8SMiguel Ojeda #[inline] 1175753dece8SMiguel Ojeda pub fn as_mut_ptr(&mut self) -> *mut T { 1176753dece8SMiguel Ojeda // We shadow the slice method of the same name to avoid going through 1177753dece8SMiguel Ojeda // `deref_mut`, which creates an intermediate reference. 1178753dece8SMiguel Ojeda let ptr = self.buf.ptr(); 1179753dece8SMiguel Ojeda unsafe { 1180753dece8SMiguel Ojeda assume(!ptr.is_null()); 1181753dece8SMiguel Ojeda } 1182753dece8SMiguel Ojeda ptr 1183753dece8SMiguel Ojeda } 1184753dece8SMiguel Ojeda 1185753dece8SMiguel Ojeda /// Returns a reference to the underlying allocator. 1186753dece8SMiguel Ojeda #[unstable(feature = "allocator_api", issue = "32838")] 1187753dece8SMiguel Ojeda #[inline] 1188753dece8SMiguel Ojeda pub fn allocator(&self) -> &A { 1189753dece8SMiguel Ojeda self.buf.allocator() 1190753dece8SMiguel Ojeda } 1191753dece8SMiguel Ojeda 1192753dece8SMiguel Ojeda /// Forces the length of the vector to `new_len`. 1193753dece8SMiguel Ojeda /// 1194753dece8SMiguel Ojeda /// This is a low-level operation that maintains none of the normal 1195753dece8SMiguel Ojeda /// invariants of the type. Normally changing the length of a vector 1196753dece8SMiguel Ojeda /// is done using one of the safe operations instead, such as 1197753dece8SMiguel Ojeda /// [`truncate`], [`resize`], [`extend`], or [`clear`]. 1198753dece8SMiguel Ojeda /// 1199753dece8SMiguel Ojeda /// [`truncate`]: Vec::truncate 1200753dece8SMiguel Ojeda /// [`resize`]: Vec::resize 1201753dece8SMiguel Ojeda /// [`extend`]: Extend::extend 1202753dece8SMiguel Ojeda /// [`clear`]: Vec::clear 1203753dece8SMiguel Ojeda /// 1204753dece8SMiguel Ojeda /// # Safety 1205753dece8SMiguel Ojeda /// 1206753dece8SMiguel Ojeda /// - `new_len` must be less than or equal to [`capacity()`]. 1207753dece8SMiguel Ojeda /// - The elements at `old_len..new_len` must be initialized. 1208753dece8SMiguel Ojeda /// 1209753dece8SMiguel Ojeda /// [`capacity()`]: Vec::capacity 1210753dece8SMiguel Ojeda /// 1211753dece8SMiguel Ojeda /// # Examples 1212753dece8SMiguel Ojeda /// 1213753dece8SMiguel Ojeda /// This method can be useful for situations in which the vector 1214753dece8SMiguel Ojeda /// is serving as a buffer for other code, particularly over FFI: 1215753dece8SMiguel Ojeda /// 1216753dece8SMiguel Ojeda /// ```no_run 1217753dece8SMiguel Ojeda /// # #![allow(dead_code)] 1218753dece8SMiguel Ojeda /// # // This is just a minimal skeleton for the doc example; 1219753dece8SMiguel Ojeda /// # // don't use this as a starting point for a real library. 1220753dece8SMiguel Ojeda /// # pub struct StreamWrapper { strm: *mut std::ffi::c_void } 1221753dece8SMiguel Ojeda /// # const Z_OK: i32 = 0; 1222753dece8SMiguel Ojeda /// # extern "C" { 1223753dece8SMiguel Ojeda /// # fn deflateGetDictionary( 1224753dece8SMiguel Ojeda /// # strm: *mut std::ffi::c_void, 1225753dece8SMiguel Ojeda /// # dictionary: *mut u8, 1226753dece8SMiguel Ojeda /// # dictLength: *mut usize, 1227753dece8SMiguel Ojeda /// # ) -> i32; 1228753dece8SMiguel Ojeda /// # } 1229753dece8SMiguel Ojeda /// # impl StreamWrapper { 1230753dece8SMiguel Ojeda /// pub fn get_dictionary(&self) -> Option<Vec<u8>> { 1231753dece8SMiguel Ojeda /// // Per the FFI method's docs, "32768 bytes is always enough". 1232753dece8SMiguel Ojeda /// let mut dict = Vec::with_capacity(32_768); 1233753dece8SMiguel Ojeda /// let mut dict_length = 0; 1234753dece8SMiguel Ojeda /// // SAFETY: When `deflateGetDictionary` returns `Z_OK`, it holds that: 1235753dece8SMiguel Ojeda /// // 1. `dict_length` elements were initialized. 1236753dece8SMiguel Ojeda /// // 2. `dict_length` <= the capacity (32_768) 1237753dece8SMiguel Ojeda /// // which makes `set_len` safe to call. 1238753dece8SMiguel Ojeda /// unsafe { 1239753dece8SMiguel Ojeda /// // Make the FFI call... 1240753dece8SMiguel Ojeda /// let r = deflateGetDictionary(self.strm, dict.as_mut_ptr(), &mut dict_length); 1241753dece8SMiguel Ojeda /// if r == Z_OK { 1242753dece8SMiguel Ojeda /// // ...and update the length to what was initialized. 1243753dece8SMiguel Ojeda /// dict.set_len(dict_length); 1244753dece8SMiguel Ojeda /// Some(dict) 1245753dece8SMiguel Ojeda /// } else { 1246753dece8SMiguel Ojeda /// None 1247753dece8SMiguel Ojeda /// } 1248753dece8SMiguel Ojeda /// } 1249753dece8SMiguel Ojeda /// } 1250753dece8SMiguel Ojeda /// # } 1251753dece8SMiguel Ojeda /// ``` 1252753dece8SMiguel Ojeda /// 1253753dece8SMiguel Ojeda /// While the following example is sound, there is a memory leak since 1254753dece8SMiguel Ojeda /// the inner vectors were not freed prior to the `set_len` call: 1255753dece8SMiguel Ojeda /// 1256753dece8SMiguel Ojeda /// ``` 1257753dece8SMiguel Ojeda /// let mut vec = vec![vec![1, 0, 0], 1258753dece8SMiguel Ojeda /// vec![0, 1, 0], 1259753dece8SMiguel Ojeda /// vec![0, 0, 1]]; 1260753dece8SMiguel Ojeda /// // SAFETY: 1261753dece8SMiguel Ojeda /// // 1. `old_len..0` is empty so no elements need to be initialized. 1262753dece8SMiguel Ojeda /// // 2. `0 <= capacity` always holds whatever `capacity` is. 1263753dece8SMiguel Ojeda /// unsafe { 1264753dece8SMiguel Ojeda /// vec.set_len(0); 1265753dece8SMiguel Ojeda /// } 1266753dece8SMiguel Ojeda /// ``` 1267753dece8SMiguel Ojeda /// 1268753dece8SMiguel Ojeda /// Normally, here, one would use [`clear`] instead to correctly drop 1269753dece8SMiguel Ojeda /// the contents and thus not leak memory. 1270753dece8SMiguel Ojeda #[inline] 1271753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1272753dece8SMiguel Ojeda pub unsafe fn set_len(&mut self, new_len: usize) { 1273753dece8SMiguel Ojeda debug_assert!(new_len <= self.capacity()); 1274753dece8SMiguel Ojeda 1275753dece8SMiguel Ojeda self.len = new_len; 1276753dece8SMiguel Ojeda } 1277753dece8SMiguel Ojeda 1278753dece8SMiguel Ojeda /// Removes an element from the vector and returns it. 1279753dece8SMiguel Ojeda /// 1280753dece8SMiguel Ojeda /// The removed element is replaced by the last element of the vector. 1281753dece8SMiguel Ojeda /// 1282753dece8SMiguel Ojeda /// This does not preserve ordering, but is *O*(1). 1283753dece8SMiguel Ojeda /// If you need to preserve the element order, use [`remove`] instead. 1284753dece8SMiguel Ojeda /// 1285753dece8SMiguel Ojeda /// [`remove`]: Vec::remove 1286753dece8SMiguel Ojeda /// 1287753dece8SMiguel Ojeda /// # Panics 1288753dece8SMiguel Ojeda /// 1289753dece8SMiguel Ojeda /// Panics if `index` is out of bounds. 1290753dece8SMiguel Ojeda /// 1291753dece8SMiguel Ojeda /// # Examples 1292753dece8SMiguel Ojeda /// 1293753dece8SMiguel Ojeda /// ``` 1294753dece8SMiguel Ojeda /// let mut v = vec!["foo", "bar", "baz", "qux"]; 1295753dece8SMiguel Ojeda /// 1296753dece8SMiguel Ojeda /// assert_eq!(v.swap_remove(1), "bar"); 1297753dece8SMiguel Ojeda /// assert_eq!(v, ["foo", "qux", "baz"]); 1298753dece8SMiguel Ojeda /// 1299753dece8SMiguel Ojeda /// assert_eq!(v.swap_remove(0), "foo"); 1300753dece8SMiguel Ojeda /// assert_eq!(v, ["baz", "qux"]); 1301753dece8SMiguel Ojeda /// ``` 1302753dece8SMiguel Ojeda #[inline] 1303753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1304753dece8SMiguel Ojeda pub fn swap_remove(&mut self, index: usize) -> T { 1305753dece8SMiguel Ojeda #[cold] 1306753dece8SMiguel Ojeda #[inline(never)] 1307753dece8SMiguel Ojeda fn assert_failed(index: usize, len: usize) -> ! { 1308753dece8SMiguel Ojeda panic!("swap_remove index (is {index}) should be < len (is {len})"); 1309753dece8SMiguel Ojeda } 1310753dece8SMiguel Ojeda 1311753dece8SMiguel Ojeda let len = self.len(); 1312753dece8SMiguel Ojeda if index >= len { 1313753dece8SMiguel Ojeda assert_failed(index, len); 1314753dece8SMiguel Ojeda } 1315753dece8SMiguel Ojeda unsafe { 1316753dece8SMiguel Ojeda // We replace self[index] with the last element. Note that if the 1317753dece8SMiguel Ojeda // bounds check above succeeds there must be a last element (which 1318753dece8SMiguel Ojeda // can be self[index] itself). 1319753dece8SMiguel Ojeda let value = ptr::read(self.as_ptr().add(index)); 1320753dece8SMiguel Ojeda let base_ptr = self.as_mut_ptr(); 1321753dece8SMiguel Ojeda ptr::copy(base_ptr.add(len - 1), base_ptr.add(index), 1); 1322753dece8SMiguel Ojeda self.set_len(len - 1); 1323753dece8SMiguel Ojeda value 1324753dece8SMiguel Ojeda } 1325753dece8SMiguel Ojeda } 1326753dece8SMiguel Ojeda 1327753dece8SMiguel Ojeda /// Inserts an element at position `index` within the vector, shifting all 1328753dece8SMiguel Ojeda /// elements after it to the right. 1329753dece8SMiguel Ojeda /// 1330753dece8SMiguel Ojeda /// # Panics 1331753dece8SMiguel Ojeda /// 1332753dece8SMiguel Ojeda /// Panics if `index > len`. 1333753dece8SMiguel Ojeda /// 1334753dece8SMiguel Ojeda /// # Examples 1335753dece8SMiguel Ojeda /// 1336753dece8SMiguel Ojeda /// ``` 1337753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3]; 1338753dece8SMiguel Ojeda /// vec.insert(1, 4); 1339753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 4, 2, 3]); 1340753dece8SMiguel Ojeda /// vec.insert(4, 5); 1341753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 4, 2, 3, 5]); 1342753dece8SMiguel Ojeda /// ``` 1343753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 1344753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1345753dece8SMiguel Ojeda pub fn insert(&mut self, index: usize, element: T) { 1346753dece8SMiguel Ojeda #[cold] 1347753dece8SMiguel Ojeda #[inline(never)] 1348753dece8SMiguel Ojeda fn assert_failed(index: usize, len: usize) -> ! { 1349753dece8SMiguel Ojeda panic!("insertion index (is {index}) should be <= len (is {len})"); 1350753dece8SMiguel Ojeda } 1351753dece8SMiguel Ojeda 1352753dece8SMiguel Ojeda let len = self.len(); 1353753dece8SMiguel Ojeda if index > len { 1354753dece8SMiguel Ojeda assert_failed(index, len); 1355753dece8SMiguel Ojeda } 1356753dece8SMiguel Ojeda 1357753dece8SMiguel Ojeda // space for the new element 1358753dece8SMiguel Ojeda if len == self.buf.capacity() { 1359753dece8SMiguel Ojeda self.reserve(1); 1360753dece8SMiguel Ojeda } 1361753dece8SMiguel Ojeda 1362753dece8SMiguel Ojeda unsafe { 1363753dece8SMiguel Ojeda // infallible 1364753dece8SMiguel Ojeda // The spot to put the new value 1365753dece8SMiguel Ojeda { 1366753dece8SMiguel Ojeda let p = self.as_mut_ptr().add(index); 1367753dece8SMiguel Ojeda // Shift everything over to make space. (Duplicating the 1368753dece8SMiguel Ojeda // `index`th element into two consecutive places.) 1369753dece8SMiguel Ojeda ptr::copy(p, p.offset(1), len - index); 1370753dece8SMiguel Ojeda // Write it in, overwriting the first copy of the `index`th 1371753dece8SMiguel Ojeda // element. 1372753dece8SMiguel Ojeda ptr::write(p, element); 1373753dece8SMiguel Ojeda } 1374753dece8SMiguel Ojeda self.set_len(len + 1); 1375753dece8SMiguel Ojeda } 1376753dece8SMiguel Ojeda } 1377753dece8SMiguel Ojeda 1378753dece8SMiguel Ojeda /// Removes and returns the element at position `index` within the vector, 1379753dece8SMiguel Ojeda /// shifting all elements after it to the left. 1380753dece8SMiguel Ojeda /// 1381753dece8SMiguel Ojeda /// Note: Because this shifts over the remaining elements, it has a 1382753dece8SMiguel Ojeda /// worst-case performance of *O*(*n*). If you don't need the order of elements 1383753dece8SMiguel Ojeda /// to be preserved, use [`swap_remove`] instead. If you'd like to remove 1384753dece8SMiguel Ojeda /// elements from the beginning of the `Vec`, consider using 1385753dece8SMiguel Ojeda /// [`VecDeque::pop_front`] instead. 1386753dece8SMiguel Ojeda /// 1387753dece8SMiguel Ojeda /// [`swap_remove`]: Vec::swap_remove 1388753dece8SMiguel Ojeda /// [`VecDeque::pop_front`]: crate::collections::VecDeque::pop_front 1389753dece8SMiguel Ojeda /// 1390753dece8SMiguel Ojeda /// # Panics 1391753dece8SMiguel Ojeda /// 1392753dece8SMiguel Ojeda /// Panics if `index` is out of bounds. 1393753dece8SMiguel Ojeda /// 1394753dece8SMiguel Ojeda /// # Examples 1395753dece8SMiguel Ojeda /// 1396753dece8SMiguel Ojeda /// ``` 1397753dece8SMiguel Ojeda /// let mut v = vec![1, 2, 3]; 1398753dece8SMiguel Ojeda /// assert_eq!(v.remove(1), 2); 1399753dece8SMiguel Ojeda /// assert_eq!(v, [1, 3]); 1400753dece8SMiguel Ojeda /// ``` 1401753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1402753dece8SMiguel Ojeda #[track_caller] 1403753dece8SMiguel Ojeda pub fn remove(&mut self, index: usize) -> T { 1404753dece8SMiguel Ojeda #[cold] 1405753dece8SMiguel Ojeda #[inline(never)] 1406753dece8SMiguel Ojeda #[track_caller] 1407753dece8SMiguel Ojeda fn assert_failed(index: usize, len: usize) -> ! { 1408753dece8SMiguel Ojeda panic!("removal index (is {index}) should be < len (is {len})"); 1409753dece8SMiguel Ojeda } 1410753dece8SMiguel Ojeda 1411753dece8SMiguel Ojeda let len = self.len(); 1412753dece8SMiguel Ojeda if index >= len { 1413753dece8SMiguel Ojeda assert_failed(index, len); 1414753dece8SMiguel Ojeda } 1415753dece8SMiguel Ojeda unsafe { 1416753dece8SMiguel Ojeda // infallible 1417753dece8SMiguel Ojeda let ret; 1418753dece8SMiguel Ojeda { 1419753dece8SMiguel Ojeda // the place we are taking from. 1420753dece8SMiguel Ojeda let ptr = self.as_mut_ptr().add(index); 1421753dece8SMiguel Ojeda // copy it out, unsafely having a copy of the value on 1422753dece8SMiguel Ojeda // the stack and in the vector at the same time. 1423753dece8SMiguel Ojeda ret = ptr::read(ptr); 1424753dece8SMiguel Ojeda 1425753dece8SMiguel Ojeda // Shift everything down to fill in that spot. 1426753dece8SMiguel Ojeda ptr::copy(ptr.offset(1), ptr, len - index - 1); 1427753dece8SMiguel Ojeda } 1428753dece8SMiguel Ojeda self.set_len(len - 1); 1429753dece8SMiguel Ojeda ret 1430753dece8SMiguel Ojeda } 1431753dece8SMiguel Ojeda } 1432753dece8SMiguel Ojeda 1433753dece8SMiguel Ojeda /// Retains only the elements specified by the predicate. 1434753dece8SMiguel Ojeda /// 1435753dece8SMiguel Ojeda /// In other words, remove all elements `e` for which `f(&e)` returns `false`. 1436753dece8SMiguel Ojeda /// This method operates in place, visiting each element exactly once in the 1437753dece8SMiguel Ojeda /// original order, and preserves the order of the retained elements. 1438753dece8SMiguel Ojeda /// 1439753dece8SMiguel Ojeda /// # Examples 1440753dece8SMiguel Ojeda /// 1441753dece8SMiguel Ojeda /// ``` 1442753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3, 4]; 1443753dece8SMiguel Ojeda /// vec.retain(|&x| x % 2 == 0); 1444753dece8SMiguel Ojeda /// assert_eq!(vec, [2, 4]); 1445753dece8SMiguel Ojeda /// ``` 1446753dece8SMiguel Ojeda /// 1447753dece8SMiguel Ojeda /// Because the elements are visited exactly once in the original order, 1448753dece8SMiguel Ojeda /// external state may be used to decide which elements to keep. 1449753dece8SMiguel Ojeda /// 1450753dece8SMiguel Ojeda /// ``` 1451753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3, 4, 5]; 1452753dece8SMiguel Ojeda /// let keep = [false, true, true, false, true]; 1453753dece8SMiguel Ojeda /// let mut iter = keep.iter(); 1454753dece8SMiguel Ojeda /// vec.retain(|_| *iter.next().unwrap()); 1455753dece8SMiguel Ojeda /// assert_eq!(vec, [2, 3, 5]); 1456753dece8SMiguel Ojeda /// ``` 1457753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1458753dece8SMiguel Ojeda pub fn retain<F>(&mut self, mut f: F) 1459753dece8SMiguel Ojeda where 1460753dece8SMiguel Ojeda F: FnMut(&T) -> bool, 1461753dece8SMiguel Ojeda { 1462753dece8SMiguel Ojeda self.retain_mut(|elem| f(elem)); 1463753dece8SMiguel Ojeda } 1464753dece8SMiguel Ojeda 1465753dece8SMiguel Ojeda /// Retains only the elements specified by the predicate, passing a mutable reference to it. 1466753dece8SMiguel Ojeda /// 1467753dece8SMiguel Ojeda /// In other words, remove all elements `e` such that `f(&mut e)` returns `false`. 1468753dece8SMiguel Ojeda /// This method operates in place, visiting each element exactly once in the 1469753dece8SMiguel Ojeda /// original order, and preserves the order of the retained elements. 1470753dece8SMiguel Ojeda /// 1471753dece8SMiguel Ojeda /// # Examples 1472753dece8SMiguel Ojeda /// 1473753dece8SMiguel Ojeda /// ``` 1474753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3, 4]; 1475753dece8SMiguel Ojeda /// vec.retain_mut(|x| if *x > 3 { 1476753dece8SMiguel Ojeda /// false 1477753dece8SMiguel Ojeda /// } else { 1478753dece8SMiguel Ojeda /// *x += 1; 1479753dece8SMiguel Ojeda /// true 1480753dece8SMiguel Ojeda /// }); 1481753dece8SMiguel Ojeda /// assert_eq!(vec, [2, 3, 4]); 1482753dece8SMiguel Ojeda /// ``` 1483753dece8SMiguel Ojeda #[stable(feature = "vec_retain_mut", since = "1.61.0")] 1484753dece8SMiguel Ojeda pub fn retain_mut<F>(&mut self, mut f: F) 1485753dece8SMiguel Ojeda where 1486753dece8SMiguel Ojeda F: FnMut(&mut T) -> bool, 1487753dece8SMiguel Ojeda { 1488753dece8SMiguel Ojeda let original_len = self.len(); 1489753dece8SMiguel Ojeda // Avoid double drop if the drop guard is not executed, 1490753dece8SMiguel Ojeda // since we may make some holes during the process. 1491753dece8SMiguel Ojeda unsafe { self.set_len(0) }; 1492753dece8SMiguel Ojeda 1493753dece8SMiguel Ojeda // Vec: [Kept, Kept, Hole, Hole, Hole, Hole, Unchecked, Unchecked] 1494753dece8SMiguel Ojeda // |<- processed len ->| ^- next to check 1495753dece8SMiguel Ojeda // |<- deleted cnt ->| 1496753dece8SMiguel Ojeda // |<- original_len ->| 1497753dece8SMiguel Ojeda // Kept: Elements which predicate returns true on. 1498753dece8SMiguel Ojeda // Hole: Moved or dropped element slot. 1499753dece8SMiguel Ojeda // Unchecked: Unchecked valid elements. 1500753dece8SMiguel Ojeda // 1501753dece8SMiguel Ojeda // This drop guard will be invoked when predicate or `drop` of element panicked. 1502753dece8SMiguel Ojeda // It shifts unchecked elements to cover holes and `set_len` to the correct length. 1503753dece8SMiguel Ojeda // In cases when predicate and `drop` never panick, it will be optimized out. 1504753dece8SMiguel Ojeda struct BackshiftOnDrop<'a, T, A: Allocator> { 1505753dece8SMiguel Ojeda v: &'a mut Vec<T, A>, 1506753dece8SMiguel Ojeda processed_len: usize, 1507753dece8SMiguel Ojeda deleted_cnt: usize, 1508753dece8SMiguel Ojeda original_len: usize, 1509753dece8SMiguel Ojeda } 1510753dece8SMiguel Ojeda 1511753dece8SMiguel Ojeda impl<T, A: Allocator> Drop for BackshiftOnDrop<'_, T, A> { 1512753dece8SMiguel Ojeda fn drop(&mut self) { 1513753dece8SMiguel Ojeda if self.deleted_cnt > 0 { 1514753dece8SMiguel Ojeda // SAFETY: Trailing unchecked items must be valid since we never touch them. 1515753dece8SMiguel Ojeda unsafe { 1516753dece8SMiguel Ojeda ptr::copy( 1517753dece8SMiguel Ojeda self.v.as_ptr().add(self.processed_len), 1518753dece8SMiguel Ojeda self.v.as_mut_ptr().add(self.processed_len - self.deleted_cnt), 1519753dece8SMiguel Ojeda self.original_len - self.processed_len, 1520753dece8SMiguel Ojeda ); 1521753dece8SMiguel Ojeda } 1522753dece8SMiguel Ojeda } 1523753dece8SMiguel Ojeda // SAFETY: After filling holes, all items are in contiguous memory. 1524753dece8SMiguel Ojeda unsafe { 1525753dece8SMiguel Ojeda self.v.set_len(self.original_len - self.deleted_cnt); 1526753dece8SMiguel Ojeda } 1527753dece8SMiguel Ojeda } 1528753dece8SMiguel Ojeda } 1529753dece8SMiguel Ojeda 1530753dece8SMiguel Ojeda let mut g = BackshiftOnDrop { v: self, processed_len: 0, deleted_cnt: 0, original_len }; 1531753dece8SMiguel Ojeda 1532753dece8SMiguel Ojeda fn process_loop<F, T, A: Allocator, const DELETED: bool>( 1533753dece8SMiguel Ojeda original_len: usize, 1534753dece8SMiguel Ojeda f: &mut F, 1535753dece8SMiguel Ojeda g: &mut BackshiftOnDrop<'_, T, A>, 1536753dece8SMiguel Ojeda ) where 1537753dece8SMiguel Ojeda F: FnMut(&mut T) -> bool, 1538753dece8SMiguel Ojeda { 1539753dece8SMiguel Ojeda while g.processed_len != original_len { 1540753dece8SMiguel Ojeda // SAFETY: Unchecked element must be valid. 1541753dece8SMiguel Ojeda let cur = unsafe { &mut *g.v.as_mut_ptr().add(g.processed_len) }; 1542753dece8SMiguel Ojeda if !f(cur) { 1543753dece8SMiguel Ojeda // Advance early to avoid double drop if `drop_in_place` panicked. 1544753dece8SMiguel Ojeda g.processed_len += 1; 1545753dece8SMiguel Ojeda g.deleted_cnt += 1; 1546753dece8SMiguel Ojeda // SAFETY: We never touch this element again after dropped. 1547753dece8SMiguel Ojeda unsafe { ptr::drop_in_place(cur) }; 1548753dece8SMiguel Ojeda // We already advanced the counter. 1549753dece8SMiguel Ojeda if DELETED { 1550753dece8SMiguel Ojeda continue; 1551753dece8SMiguel Ojeda } else { 1552753dece8SMiguel Ojeda break; 1553753dece8SMiguel Ojeda } 1554753dece8SMiguel Ojeda } 1555753dece8SMiguel Ojeda if DELETED { 1556753dece8SMiguel Ojeda // SAFETY: `deleted_cnt` > 0, so the hole slot must not overlap with current element. 1557753dece8SMiguel Ojeda // We use copy for move, and never touch this element again. 1558753dece8SMiguel Ojeda unsafe { 1559753dece8SMiguel Ojeda let hole_slot = g.v.as_mut_ptr().add(g.processed_len - g.deleted_cnt); 1560753dece8SMiguel Ojeda ptr::copy_nonoverlapping(cur, hole_slot, 1); 1561753dece8SMiguel Ojeda } 1562753dece8SMiguel Ojeda } 1563753dece8SMiguel Ojeda g.processed_len += 1; 1564753dece8SMiguel Ojeda } 1565753dece8SMiguel Ojeda } 1566753dece8SMiguel Ojeda 1567753dece8SMiguel Ojeda // Stage 1: Nothing was deleted. 1568753dece8SMiguel Ojeda process_loop::<F, T, A, false>(original_len, &mut f, &mut g); 1569753dece8SMiguel Ojeda 1570753dece8SMiguel Ojeda // Stage 2: Some elements were deleted. 1571753dece8SMiguel Ojeda process_loop::<F, T, A, true>(original_len, &mut f, &mut g); 1572753dece8SMiguel Ojeda 1573753dece8SMiguel Ojeda // All item are processed. This can be optimized to `set_len` by LLVM. 1574753dece8SMiguel Ojeda drop(g); 1575753dece8SMiguel Ojeda } 1576753dece8SMiguel Ojeda 1577753dece8SMiguel Ojeda /// Removes all but the first of consecutive elements in the vector that resolve to the same 1578753dece8SMiguel Ojeda /// key. 1579753dece8SMiguel Ojeda /// 1580753dece8SMiguel Ojeda /// If the vector is sorted, this removes all duplicates. 1581753dece8SMiguel Ojeda /// 1582753dece8SMiguel Ojeda /// # Examples 1583753dece8SMiguel Ojeda /// 1584753dece8SMiguel Ojeda /// ``` 1585753dece8SMiguel Ojeda /// let mut vec = vec![10, 20, 21, 30, 20]; 1586753dece8SMiguel Ojeda /// 1587753dece8SMiguel Ojeda /// vec.dedup_by_key(|i| *i / 10); 1588753dece8SMiguel Ojeda /// 1589753dece8SMiguel Ojeda /// assert_eq!(vec, [10, 20, 30, 20]); 1590753dece8SMiguel Ojeda /// ``` 1591753dece8SMiguel Ojeda #[stable(feature = "dedup_by", since = "1.16.0")] 1592753dece8SMiguel Ojeda #[inline] 1593753dece8SMiguel Ojeda pub fn dedup_by_key<F, K>(&mut self, mut key: F) 1594753dece8SMiguel Ojeda where 1595753dece8SMiguel Ojeda F: FnMut(&mut T) -> K, 1596753dece8SMiguel Ojeda K: PartialEq, 1597753dece8SMiguel Ojeda { 1598753dece8SMiguel Ojeda self.dedup_by(|a, b| key(a) == key(b)) 1599753dece8SMiguel Ojeda } 1600753dece8SMiguel Ojeda 1601753dece8SMiguel Ojeda /// Removes all but the first of consecutive elements in the vector satisfying a given equality 1602753dece8SMiguel Ojeda /// relation. 1603753dece8SMiguel Ojeda /// 1604753dece8SMiguel Ojeda /// The `same_bucket` function is passed references to two elements from the vector and 1605753dece8SMiguel Ojeda /// must determine if the elements compare equal. The elements are passed in opposite order 1606753dece8SMiguel Ojeda /// from their order in the slice, so if `same_bucket(a, b)` returns `true`, `a` is removed. 1607753dece8SMiguel Ojeda /// 1608753dece8SMiguel Ojeda /// If the vector is sorted, this removes all duplicates. 1609753dece8SMiguel Ojeda /// 1610753dece8SMiguel Ojeda /// # Examples 1611753dece8SMiguel Ojeda /// 1612753dece8SMiguel Ojeda /// ``` 1613753dece8SMiguel Ojeda /// let mut vec = vec!["foo", "bar", "Bar", "baz", "bar"]; 1614753dece8SMiguel Ojeda /// 1615753dece8SMiguel Ojeda /// vec.dedup_by(|a, b| a.eq_ignore_ascii_case(b)); 1616753dece8SMiguel Ojeda /// 1617753dece8SMiguel Ojeda /// assert_eq!(vec, ["foo", "bar", "baz", "bar"]); 1618753dece8SMiguel Ojeda /// ``` 1619753dece8SMiguel Ojeda #[stable(feature = "dedup_by", since = "1.16.0")] 1620753dece8SMiguel Ojeda pub fn dedup_by<F>(&mut self, mut same_bucket: F) 1621753dece8SMiguel Ojeda where 1622753dece8SMiguel Ojeda F: FnMut(&mut T, &mut T) -> bool, 1623753dece8SMiguel Ojeda { 1624753dece8SMiguel Ojeda let len = self.len(); 1625753dece8SMiguel Ojeda if len <= 1 { 1626753dece8SMiguel Ojeda return; 1627753dece8SMiguel Ojeda } 1628753dece8SMiguel Ojeda 1629753dece8SMiguel Ojeda /* INVARIANT: vec.len() > read >= write > write-1 >= 0 */ 1630753dece8SMiguel Ojeda struct FillGapOnDrop<'a, T, A: core::alloc::Allocator> { 1631753dece8SMiguel Ojeda /* Offset of the element we want to check if it is duplicate */ 1632753dece8SMiguel Ojeda read: usize, 1633753dece8SMiguel Ojeda 1634753dece8SMiguel Ojeda /* Offset of the place where we want to place the non-duplicate 1635753dece8SMiguel Ojeda * when we find it. */ 1636753dece8SMiguel Ojeda write: usize, 1637753dece8SMiguel Ojeda 1638753dece8SMiguel Ojeda /* The Vec that would need correction if `same_bucket` panicked */ 1639753dece8SMiguel Ojeda vec: &'a mut Vec<T, A>, 1640753dece8SMiguel Ojeda } 1641753dece8SMiguel Ojeda 1642753dece8SMiguel Ojeda impl<'a, T, A: core::alloc::Allocator> Drop for FillGapOnDrop<'a, T, A> { 1643753dece8SMiguel Ojeda fn drop(&mut self) { 1644753dece8SMiguel Ojeda /* This code gets executed when `same_bucket` panics */ 1645753dece8SMiguel Ojeda 1646753dece8SMiguel Ojeda /* SAFETY: invariant guarantees that `read - write` 1647753dece8SMiguel Ojeda * and `len - read` never overflow and that the copy is always 1648753dece8SMiguel Ojeda * in-bounds. */ 1649753dece8SMiguel Ojeda unsafe { 1650753dece8SMiguel Ojeda let ptr = self.vec.as_mut_ptr(); 1651753dece8SMiguel Ojeda let len = self.vec.len(); 1652753dece8SMiguel Ojeda 1653753dece8SMiguel Ojeda /* How many items were left when `same_bucket` panicked. 1654753dece8SMiguel Ojeda * Basically vec[read..].len() */ 1655753dece8SMiguel Ojeda let items_left = len.wrapping_sub(self.read); 1656753dece8SMiguel Ojeda 1657753dece8SMiguel Ojeda /* Pointer to first item in vec[write..write+items_left] slice */ 1658753dece8SMiguel Ojeda let dropped_ptr = ptr.add(self.write); 1659753dece8SMiguel Ojeda /* Pointer to first item in vec[read..] slice */ 1660753dece8SMiguel Ojeda let valid_ptr = ptr.add(self.read); 1661753dece8SMiguel Ojeda 1662753dece8SMiguel Ojeda /* Copy `vec[read..]` to `vec[write..write+items_left]`. 1663753dece8SMiguel Ojeda * The slices can overlap, so `copy_nonoverlapping` cannot be used */ 1664753dece8SMiguel Ojeda ptr::copy(valid_ptr, dropped_ptr, items_left); 1665753dece8SMiguel Ojeda 1666753dece8SMiguel Ojeda /* How many items have been already dropped 1667753dece8SMiguel Ojeda * Basically vec[read..write].len() */ 1668753dece8SMiguel Ojeda let dropped = self.read.wrapping_sub(self.write); 1669753dece8SMiguel Ojeda 1670753dece8SMiguel Ojeda self.vec.set_len(len - dropped); 1671753dece8SMiguel Ojeda } 1672753dece8SMiguel Ojeda } 1673753dece8SMiguel Ojeda } 1674753dece8SMiguel Ojeda 1675753dece8SMiguel Ojeda let mut gap = FillGapOnDrop { read: 1, write: 1, vec: self }; 1676753dece8SMiguel Ojeda let ptr = gap.vec.as_mut_ptr(); 1677753dece8SMiguel Ojeda 1678753dece8SMiguel Ojeda /* Drop items while going through Vec, it should be more efficient than 1679753dece8SMiguel Ojeda * doing slice partition_dedup + truncate */ 1680753dece8SMiguel Ojeda 1681753dece8SMiguel Ojeda /* SAFETY: Because of the invariant, read_ptr, prev_ptr and write_ptr 1682753dece8SMiguel Ojeda * are always in-bounds and read_ptr never aliases prev_ptr */ 1683753dece8SMiguel Ojeda unsafe { 1684753dece8SMiguel Ojeda while gap.read < len { 1685753dece8SMiguel Ojeda let read_ptr = ptr.add(gap.read); 1686753dece8SMiguel Ojeda let prev_ptr = ptr.add(gap.write.wrapping_sub(1)); 1687753dece8SMiguel Ojeda 1688753dece8SMiguel Ojeda if same_bucket(&mut *read_ptr, &mut *prev_ptr) { 1689753dece8SMiguel Ojeda // Increase `gap.read` now since the drop may panic. 1690753dece8SMiguel Ojeda gap.read += 1; 1691753dece8SMiguel Ojeda /* We have found duplicate, drop it in-place */ 1692753dece8SMiguel Ojeda ptr::drop_in_place(read_ptr); 1693753dece8SMiguel Ojeda } else { 1694753dece8SMiguel Ojeda let write_ptr = ptr.add(gap.write); 1695753dece8SMiguel Ojeda 1696753dece8SMiguel Ojeda /* Because `read_ptr` can be equal to `write_ptr`, we either 1697753dece8SMiguel Ojeda * have to use `copy` or conditional `copy_nonoverlapping`. 1698753dece8SMiguel Ojeda * Looks like the first option is faster. */ 1699753dece8SMiguel Ojeda ptr::copy(read_ptr, write_ptr, 1); 1700753dece8SMiguel Ojeda 1701753dece8SMiguel Ojeda /* We have filled that place, so go further */ 1702753dece8SMiguel Ojeda gap.write += 1; 1703753dece8SMiguel Ojeda gap.read += 1; 1704753dece8SMiguel Ojeda } 1705753dece8SMiguel Ojeda } 1706753dece8SMiguel Ojeda 1707753dece8SMiguel Ojeda /* Technically we could let `gap` clean up with its Drop, but 1708753dece8SMiguel Ojeda * when `same_bucket` is guaranteed to not panic, this bloats a little 1709753dece8SMiguel Ojeda * the codegen, so we just do it manually */ 1710753dece8SMiguel Ojeda gap.vec.set_len(gap.write); 1711753dece8SMiguel Ojeda mem::forget(gap); 1712753dece8SMiguel Ojeda } 1713753dece8SMiguel Ojeda } 1714753dece8SMiguel Ojeda 1715753dece8SMiguel Ojeda /// Appends an element to the back of a collection. 1716753dece8SMiguel Ojeda /// 1717753dece8SMiguel Ojeda /// # Panics 1718753dece8SMiguel Ojeda /// 1719753dece8SMiguel Ojeda /// Panics if the new capacity exceeds `isize::MAX` bytes. 1720753dece8SMiguel Ojeda /// 1721753dece8SMiguel Ojeda /// # Examples 1722753dece8SMiguel Ojeda /// 1723753dece8SMiguel Ojeda /// ``` 1724753dece8SMiguel Ojeda /// let mut vec = vec![1, 2]; 1725753dece8SMiguel Ojeda /// vec.push(3); 1726753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2, 3]); 1727753dece8SMiguel Ojeda /// ``` 1728753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 1729753dece8SMiguel Ojeda #[inline] 1730753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1731753dece8SMiguel Ojeda pub fn push(&mut self, value: T) { 1732753dece8SMiguel Ojeda // This will panic or abort if we would allocate > isize::MAX bytes 1733753dece8SMiguel Ojeda // or if the length increment would overflow for zero-sized types. 1734753dece8SMiguel Ojeda if self.len == self.buf.capacity() { 1735753dece8SMiguel Ojeda self.buf.reserve_for_push(self.len); 1736753dece8SMiguel Ojeda } 1737753dece8SMiguel Ojeda unsafe { 1738753dece8SMiguel Ojeda let end = self.as_mut_ptr().add(self.len); 1739753dece8SMiguel Ojeda ptr::write(end, value); 1740753dece8SMiguel Ojeda self.len += 1; 1741753dece8SMiguel Ojeda } 1742753dece8SMiguel Ojeda } 1743753dece8SMiguel Ojeda 1744*057b8d25SMiguel Ojeda /// Tries to append an element to the back of a collection. 1745*057b8d25SMiguel Ojeda /// 1746*057b8d25SMiguel Ojeda /// # Examples 1747*057b8d25SMiguel Ojeda /// 1748*057b8d25SMiguel Ojeda /// ``` 1749*057b8d25SMiguel Ojeda /// let mut vec = vec![1, 2]; 1750*057b8d25SMiguel Ojeda /// vec.try_push(3).unwrap(); 1751*057b8d25SMiguel Ojeda /// assert_eq!(vec, [1, 2, 3]); 1752*057b8d25SMiguel Ojeda /// ``` 1753*057b8d25SMiguel Ojeda #[inline] 1754*057b8d25SMiguel Ojeda #[stable(feature = "kernel", since = "1.0.0")] 1755*057b8d25SMiguel Ojeda pub fn try_push(&mut self, value: T) -> Result<(), TryReserveError> { 1756*057b8d25SMiguel Ojeda if self.len == self.buf.capacity() { 1757*057b8d25SMiguel Ojeda self.buf.try_reserve_for_push(self.len)?; 1758*057b8d25SMiguel Ojeda } 1759*057b8d25SMiguel Ojeda unsafe { 1760*057b8d25SMiguel Ojeda let end = self.as_mut_ptr().add(self.len); 1761*057b8d25SMiguel Ojeda ptr::write(end, value); 1762*057b8d25SMiguel Ojeda self.len += 1; 1763*057b8d25SMiguel Ojeda } 1764*057b8d25SMiguel Ojeda Ok(()) 1765*057b8d25SMiguel Ojeda } 1766*057b8d25SMiguel Ojeda 1767753dece8SMiguel Ojeda /// Removes the last element from a vector and returns it, or [`None`] if it 1768753dece8SMiguel Ojeda /// is empty. 1769753dece8SMiguel Ojeda /// 1770753dece8SMiguel Ojeda /// If you'd like to pop the first element, consider using 1771753dece8SMiguel Ojeda /// [`VecDeque::pop_front`] instead. 1772753dece8SMiguel Ojeda /// 1773753dece8SMiguel Ojeda /// [`VecDeque::pop_front`]: crate::collections::VecDeque::pop_front 1774753dece8SMiguel Ojeda /// 1775753dece8SMiguel Ojeda /// # Examples 1776753dece8SMiguel Ojeda /// 1777753dece8SMiguel Ojeda /// ``` 1778753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3]; 1779753dece8SMiguel Ojeda /// assert_eq!(vec.pop(), Some(3)); 1780753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2]); 1781753dece8SMiguel Ojeda /// ``` 1782753dece8SMiguel Ojeda #[inline] 1783753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1784753dece8SMiguel Ojeda pub fn pop(&mut self) -> Option<T> { 1785753dece8SMiguel Ojeda if self.len == 0 { 1786753dece8SMiguel Ojeda None 1787753dece8SMiguel Ojeda } else { 1788753dece8SMiguel Ojeda unsafe { 1789753dece8SMiguel Ojeda self.len -= 1; 1790753dece8SMiguel Ojeda Some(ptr::read(self.as_ptr().add(self.len()))) 1791753dece8SMiguel Ojeda } 1792753dece8SMiguel Ojeda } 1793753dece8SMiguel Ojeda } 1794753dece8SMiguel Ojeda 1795753dece8SMiguel Ojeda /// Moves all the elements of `other` into `self`, leaving `other` empty. 1796753dece8SMiguel Ojeda /// 1797753dece8SMiguel Ojeda /// # Panics 1798753dece8SMiguel Ojeda /// 1799753dece8SMiguel Ojeda /// Panics if the number of elements in the vector overflows a `usize`. 1800753dece8SMiguel Ojeda /// 1801753dece8SMiguel Ojeda /// # Examples 1802753dece8SMiguel Ojeda /// 1803753dece8SMiguel Ojeda /// ``` 1804753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3]; 1805753dece8SMiguel Ojeda /// let mut vec2 = vec![4, 5, 6]; 1806753dece8SMiguel Ojeda /// vec.append(&mut vec2); 1807753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2, 3, 4, 5, 6]); 1808753dece8SMiguel Ojeda /// assert_eq!(vec2, []); 1809753dece8SMiguel Ojeda /// ``` 1810753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 1811753dece8SMiguel Ojeda #[inline] 1812753dece8SMiguel Ojeda #[stable(feature = "append", since = "1.4.0")] 1813753dece8SMiguel Ojeda pub fn append(&mut self, other: &mut Self) { 1814753dece8SMiguel Ojeda unsafe { 1815753dece8SMiguel Ojeda self.append_elements(other.as_slice() as _); 1816753dece8SMiguel Ojeda other.set_len(0); 1817753dece8SMiguel Ojeda } 1818753dece8SMiguel Ojeda } 1819753dece8SMiguel Ojeda 1820753dece8SMiguel Ojeda /// Appends elements to `self` from other buffer. 1821753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 1822753dece8SMiguel Ojeda #[inline] 1823753dece8SMiguel Ojeda unsafe fn append_elements(&mut self, other: *const [T]) { 1824753dece8SMiguel Ojeda let count = unsafe { (*other).len() }; 1825753dece8SMiguel Ojeda self.reserve(count); 1826753dece8SMiguel Ojeda let len = self.len(); 1827753dece8SMiguel Ojeda unsafe { ptr::copy_nonoverlapping(other as *const T, self.as_mut_ptr().add(len), count) }; 1828753dece8SMiguel Ojeda self.len += count; 1829753dece8SMiguel Ojeda } 1830753dece8SMiguel Ojeda 1831753dece8SMiguel Ojeda /// Removes the specified range from the vector in bulk, returning all 1832753dece8SMiguel Ojeda /// removed elements as an iterator. If the iterator is dropped before 1833753dece8SMiguel Ojeda /// being fully consumed, it drops the remaining removed elements. 1834753dece8SMiguel Ojeda /// 1835753dece8SMiguel Ojeda /// The returned iterator keeps a mutable borrow on the vector to optimize 1836753dece8SMiguel Ojeda /// its implementation. 1837753dece8SMiguel Ojeda /// 1838753dece8SMiguel Ojeda /// # Panics 1839753dece8SMiguel Ojeda /// 1840753dece8SMiguel Ojeda /// Panics if the starting point is greater than the end point or if 1841753dece8SMiguel Ojeda /// the end point is greater than the length of the vector. 1842753dece8SMiguel Ojeda /// 1843753dece8SMiguel Ojeda /// # Leaking 1844753dece8SMiguel Ojeda /// 1845753dece8SMiguel Ojeda /// If the returned iterator goes out of scope without being dropped (due to 1846753dece8SMiguel Ojeda /// [`mem::forget`], for example), the vector may have lost and leaked 1847753dece8SMiguel Ojeda /// elements arbitrarily, including elements outside the range. 1848753dece8SMiguel Ojeda /// 1849753dece8SMiguel Ojeda /// # Examples 1850753dece8SMiguel Ojeda /// 1851753dece8SMiguel Ojeda /// ``` 1852753dece8SMiguel Ojeda /// let mut v = vec![1, 2, 3]; 1853753dece8SMiguel Ojeda /// let u: Vec<_> = v.drain(1..).collect(); 1854753dece8SMiguel Ojeda /// assert_eq!(v, &[1]); 1855753dece8SMiguel Ojeda /// assert_eq!(u, &[2, 3]); 1856753dece8SMiguel Ojeda /// 1857753dece8SMiguel Ojeda /// // A full range clears the vector, like `clear()` does 1858753dece8SMiguel Ojeda /// v.drain(..); 1859753dece8SMiguel Ojeda /// assert_eq!(v, &[]); 1860753dece8SMiguel Ojeda /// ``` 1861753dece8SMiguel Ojeda #[stable(feature = "drain", since = "1.6.0")] 1862753dece8SMiguel Ojeda pub fn drain<R>(&mut self, range: R) -> Drain<'_, T, A> 1863753dece8SMiguel Ojeda where 1864753dece8SMiguel Ojeda R: RangeBounds<usize>, 1865753dece8SMiguel Ojeda { 1866753dece8SMiguel Ojeda // Memory safety 1867753dece8SMiguel Ojeda // 1868753dece8SMiguel Ojeda // When the Drain is first created, it shortens the length of 1869753dece8SMiguel Ojeda // the source vector to make sure no uninitialized or moved-from elements 1870753dece8SMiguel Ojeda // are accessible at all if the Drain's destructor never gets to run. 1871753dece8SMiguel Ojeda // 1872753dece8SMiguel Ojeda // Drain will ptr::read out the values to remove. 1873753dece8SMiguel Ojeda // When finished, remaining tail of the vec is copied back to cover 1874753dece8SMiguel Ojeda // the hole, and the vector length is restored to the new length. 1875753dece8SMiguel Ojeda // 1876753dece8SMiguel Ojeda let len = self.len(); 1877753dece8SMiguel Ojeda let Range { start, end } = slice::range(range, ..len); 1878753dece8SMiguel Ojeda 1879753dece8SMiguel Ojeda unsafe { 1880753dece8SMiguel Ojeda // set self.vec length's to start, to be safe in case Drain is leaked 1881753dece8SMiguel Ojeda self.set_len(start); 1882753dece8SMiguel Ojeda // Use the borrow in the IterMut to indicate borrowing behavior of the 1883753dece8SMiguel Ojeda // whole Drain iterator (like &mut T). 1884753dece8SMiguel Ojeda let range_slice = slice::from_raw_parts_mut(self.as_mut_ptr().add(start), end - start); 1885753dece8SMiguel Ojeda Drain { 1886753dece8SMiguel Ojeda tail_start: end, 1887753dece8SMiguel Ojeda tail_len: len - end, 1888753dece8SMiguel Ojeda iter: range_slice.iter(), 1889753dece8SMiguel Ojeda vec: NonNull::from(self), 1890753dece8SMiguel Ojeda } 1891753dece8SMiguel Ojeda } 1892753dece8SMiguel Ojeda } 1893753dece8SMiguel Ojeda 1894753dece8SMiguel Ojeda /// Clears the vector, removing all values. 1895753dece8SMiguel Ojeda /// 1896753dece8SMiguel Ojeda /// Note that this method has no effect on the allocated capacity 1897753dece8SMiguel Ojeda /// of the vector. 1898753dece8SMiguel Ojeda /// 1899753dece8SMiguel Ojeda /// # Examples 1900753dece8SMiguel Ojeda /// 1901753dece8SMiguel Ojeda /// ``` 1902753dece8SMiguel Ojeda /// let mut v = vec![1, 2, 3]; 1903753dece8SMiguel Ojeda /// 1904753dece8SMiguel Ojeda /// v.clear(); 1905753dece8SMiguel Ojeda /// 1906753dece8SMiguel Ojeda /// assert!(v.is_empty()); 1907753dece8SMiguel Ojeda /// ``` 1908753dece8SMiguel Ojeda #[inline] 1909753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1910753dece8SMiguel Ojeda pub fn clear(&mut self) { 1911753dece8SMiguel Ojeda let elems: *mut [T] = self.as_mut_slice(); 1912753dece8SMiguel Ojeda 1913753dece8SMiguel Ojeda // SAFETY: 1914753dece8SMiguel Ojeda // - `elems` comes directly from `as_mut_slice` and is therefore valid. 1915753dece8SMiguel Ojeda // - Setting `self.len` before calling `drop_in_place` means that, 1916753dece8SMiguel Ojeda // if an element's `Drop` impl panics, the vector's `Drop` impl will 1917753dece8SMiguel Ojeda // do nothing (leaking the rest of the elements) instead of dropping 1918753dece8SMiguel Ojeda // some twice. 1919753dece8SMiguel Ojeda unsafe { 1920753dece8SMiguel Ojeda self.len = 0; 1921753dece8SMiguel Ojeda ptr::drop_in_place(elems); 1922753dece8SMiguel Ojeda } 1923753dece8SMiguel Ojeda } 1924753dece8SMiguel Ojeda 1925753dece8SMiguel Ojeda /// Returns the number of elements in the vector, also referred to 1926753dece8SMiguel Ojeda /// as its 'length'. 1927753dece8SMiguel Ojeda /// 1928753dece8SMiguel Ojeda /// # Examples 1929753dece8SMiguel Ojeda /// 1930753dece8SMiguel Ojeda /// ``` 1931753dece8SMiguel Ojeda /// let a = vec![1, 2, 3]; 1932753dece8SMiguel Ojeda /// assert_eq!(a.len(), 3); 1933753dece8SMiguel Ojeda /// ``` 1934753dece8SMiguel Ojeda #[inline] 1935753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1936753dece8SMiguel Ojeda pub fn len(&self) -> usize { 1937753dece8SMiguel Ojeda self.len 1938753dece8SMiguel Ojeda } 1939753dece8SMiguel Ojeda 1940753dece8SMiguel Ojeda /// Returns `true` if the vector contains no elements. 1941753dece8SMiguel Ojeda /// 1942753dece8SMiguel Ojeda /// # Examples 1943753dece8SMiguel Ojeda /// 1944753dece8SMiguel Ojeda /// ``` 1945753dece8SMiguel Ojeda /// let mut v = Vec::new(); 1946753dece8SMiguel Ojeda /// assert!(v.is_empty()); 1947753dece8SMiguel Ojeda /// 1948753dece8SMiguel Ojeda /// v.push(1); 1949753dece8SMiguel Ojeda /// assert!(!v.is_empty()); 1950753dece8SMiguel Ojeda /// ``` 1951753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 1952753dece8SMiguel Ojeda pub fn is_empty(&self) -> bool { 1953753dece8SMiguel Ojeda self.len() == 0 1954753dece8SMiguel Ojeda } 1955753dece8SMiguel Ojeda 1956753dece8SMiguel Ojeda /// Splits the collection into two at the given index. 1957753dece8SMiguel Ojeda /// 1958753dece8SMiguel Ojeda /// Returns a newly allocated vector containing the elements in the range 1959753dece8SMiguel Ojeda /// `[at, len)`. After the call, the original vector will be left containing 1960753dece8SMiguel Ojeda /// the elements `[0, at)` with its previous capacity unchanged. 1961753dece8SMiguel Ojeda /// 1962753dece8SMiguel Ojeda /// # Panics 1963753dece8SMiguel Ojeda /// 1964753dece8SMiguel Ojeda /// Panics if `at > len`. 1965753dece8SMiguel Ojeda /// 1966753dece8SMiguel Ojeda /// # Examples 1967753dece8SMiguel Ojeda /// 1968753dece8SMiguel Ojeda /// ``` 1969753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3]; 1970753dece8SMiguel Ojeda /// let vec2 = vec.split_off(1); 1971753dece8SMiguel Ojeda /// assert_eq!(vec, [1]); 1972753dece8SMiguel Ojeda /// assert_eq!(vec2, [2, 3]); 1973753dece8SMiguel Ojeda /// ``` 1974753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 1975753dece8SMiguel Ojeda #[inline] 1976753dece8SMiguel Ojeda #[must_use = "use `.truncate()` if you don't need the other half"] 1977753dece8SMiguel Ojeda #[stable(feature = "split_off", since = "1.4.0")] 1978753dece8SMiguel Ojeda pub fn split_off(&mut self, at: usize) -> Self 1979753dece8SMiguel Ojeda where 1980753dece8SMiguel Ojeda A: Clone, 1981753dece8SMiguel Ojeda { 1982753dece8SMiguel Ojeda #[cold] 1983753dece8SMiguel Ojeda #[inline(never)] 1984753dece8SMiguel Ojeda fn assert_failed(at: usize, len: usize) -> ! { 1985753dece8SMiguel Ojeda panic!("`at` split index (is {at}) should be <= len (is {len})"); 1986753dece8SMiguel Ojeda } 1987753dece8SMiguel Ojeda 1988753dece8SMiguel Ojeda if at > self.len() { 1989753dece8SMiguel Ojeda assert_failed(at, self.len()); 1990753dece8SMiguel Ojeda } 1991753dece8SMiguel Ojeda 1992753dece8SMiguel Ojeda if at == 0 { 1993753dece8SMiguel Ojeda // the new vector can take over the original buffer and avoid the copy 1994753dece8SMiguel Ojeda return mem::replace( 1995753dece8SMiguel Ojeda self, 1996753dece8SMiguel Ojeda Vec::with_capacity_in(self.capacity(), self.allocator().clone()), 1997753dece8SMiguel Ojeda ); 1998753dece8SMiguel Ojeda } 1999753dece8SMiguel Ojeda 2000753dece8SMiguel Ojeda let other_len = self.len - at; 2001753dece8SMiguel Ojeda let mut other = Vec::with_capacity_in(other_len, self.allocator().clone()); 2002753dece8SMiguel Ojeda 2003753dece8SMiguel Ojeda // Unsafely `set_len` and copy items to `other`. 2004753dece8SMiguel Ojeda unsafe { 2005753dece8SMiguel Ojeda self.set_len(at); 2006753dece8SMiguel Ojeda other.set_len(other_len); 2007753dece8SMiguel Ojeda 2008753dece8SMiguel Ojeda ptr::copy_nonoverlapping(self.as_ptr().add(at), other.as_mut_ptr(), other.len()); 2009753dece8SMiguel Ojeda } 2010753dece8SMiguel Ojeda other 2011753dece8SMiguel Ojeda } 2012753dece8SMiguel Ojeda 2013753dece8SMiguel Ojeda /// Resizes the `Vec` in-place so that `len` is equal to `new_len`. 2014753dece8SMiguel Ojeda /// 2015753dece8SMiguel Ojeda /// If `new_len` is greater than `len`, the `Vec` is extended by the 2016753dece8SMiguel Ojeda /// difference, with each additional slot filled with the result of 2017753dece8SMiguel Ojeda /// calling the closure `f`. The return values from `f` will end up 2018753dece8SMiguel Ojeda /// in the `Vec` in the order they have been generated. 2019753dece8SMiguel Ojeda /// 2020753dece8SMiguel Ojeda /// If `new_len` is less than `len`, the `Vec` is simply truncated. 2021753dece8SMiguel Ojeda /// 2022753dece8SMiguel Ojeda /// This method uses a closure to create new values on every push. If 2023753dece8SMiguel Ojeda /// you'd rather [`Clone`] a given value, use [`Vec::resize`]. If you 2024753dece8SMiguel Ojeda /// want to use the [`Default`] trait to generate values, you can 2025753dece8SMiguel Ojeda /// pass [`Default::default`] as the second argument. 2026753dece8SMiguel Ojeda /// 2027753dece8SMiguel Ojeda /// # Examples 2028753dece8SMiguel Ojeda /// 2029753dece8SMiguel Ojeda /// ``` 2030753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3]; 2031753dece8SMiguel Ojeda /// vec.resize_with(5, Default::default); 2032753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2, 3, 0, 0]); 2033753dece8SMiguel Ojeda /// 2034753dece8SMiguel Ojeda /// let mut vec = vec![]; 2035753dece8SMiguel Ojeda /// let mut p = 1; 2036753dece8SMiguel Ojeda /// vec.resize_with(4, || { p *= 2; p }); 2037753dece8SMiguel Ojeda /// assert_eq!(vec, [2, 4, 8, 16]); 2038753dece8SMiguel Ojeda /// ``` 2039753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2040753dece8SMiguel Ojeda #[stable(feature = "vec_resize_with", since = "1.33.0")] 2041753dece8SMiguel Ojeda pub fn resize_with<F>(&mut self, new_len: usize, f: F) 2042753dece8SMiguel Ojeda where 2043753dece8SMiguel Ojeda F: FnMut() -> T, 2044753dece8SMiguel Ojeda { 2045753dece8SMiguel Ojeda let len = self.len(); 2046753dece8SMiguel Ojeda if new_len > len { 2047753dece8SMiguel Ojeda self.extend_with(new_len - len, ExtendFunc(f)); 2048753dece8SMiguel Ojeda } else { 2049753dece8SMiguel Ojeda self.truncate(new_len); 2050753dece8SMiguel Ojeda } 2051753dece8SMiguel Ojeda } 2052753dece8SMiguel Ojeda 2053753dece8SMiguel Ojeda /// Consumes and leaks the `Vec`, returning a mutable reference to the contents, 2054753dece8SMiguel Ojeda /// `&'a mut [T]`. Note that the type `T` must outlive the chosen lifetime 2055753dece8SMiguel Ojeda /// `'a`. If the type has only static references, or none at all, then this 2056753dece8SMiguel Ojeda /// may be chosen to be `'static`. 2057753dece8SMiguel Ojeda /// 2058753dece8SMiguel Ojeda /// As of Rust 1.57, this method does not reallocate or shrink the `Vec`, 2059753dece8SMiguel Ojeda /// so the leaked allocation may include unused capacity that is not part 2060753dece8SMiguel Ojeda /// of the returned slice. 2061753dece8SMiguel Ojeda /// 2062753dece8SMiguel Ojeda /// This function is mainly useful for data that lives for the remainder of 2063753dece8SMiguel Ojeda /// the program's life. Dropping the returned reference will cause a memory 2064753dece8SMiguel Ojeda /// leak. 2065753dece8SMiguel Ojeda /// 2066753dece8SMiguel Ojeda /// # Examples 2067753dece8SMiguel Ojeda /// 2068753dece8SMiguel Ojeda /// Simple usage: 2069753dece8SMiguel Ojeda /// 2070753dece8SMiguel Ojeda /// ``` 2071753dece8SMiguel Ojeda /// let x = vec![1, 2, 3]; 2072753dece8SMiguel Ojeda /// let static_ref: &'static mut [usize] = x.leak(); 2073753dece8SMiguel Ojeda /// static_ref[0] += 1; 2074753dece8SMiguel Ojeda /// assert_eq!(static_ref, &[2, 2, 3]); 2075753dece8SMiguel Ojeda /// ``` 2076753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2077753dece8SMiguel Ojeda #[stable(feature = "vec_leak", since = "1.47.0")] 2078753dece8SMiguel Ojeda #[inline] 2079753dece8SMiguel Ojeda pub fn leak<'a>(self) -> &'a mut [T] 2080753dece8SMiguel Ojeda where 2081753dece8SMiguel Ojeda A: 'a, 2082753dece8SMiguel Ojeda { 2083753dece8SMiguel Ojeda let mut me = ManuallyDrop::new(self); 2084753dece8SMiguel Ojeda unsafe { slice::from_raw_parts_mut(me.as_mut_ptr(), me.len) } 2085753dece8SMiguel Ojeda } 2086753dece8SMiguel Ojeda 2087753dece8SMiguel Ojeda /// Returns the remaining spare capacity of the vector as a slice of 2088753dece8SMiguel Ojeda /// `MaybeUninit<T>`. 2089753dece8SMiguel Ojeda /// 2090753dece8SMiguel Ojeda /// The returned slice can be used to fill the vector with data (e.g. by 2091753dece8SMiguel Ojeda /// reading from a file) before marking the data as initialized using the 2092753dece8SMiguel Ojeda /// [`set_len`] method. 2093753dece8SMiguel Ojeda /// 2094753dece8SMiguel Ojeda /// [`set_len`]: Vec::set_len 2095753dece8SMiguel Ojeda /// 2096753dece8SMiguel Ojeda /// # Examples 2097753dece8SMiguel Ojeda /// 2098753dece8SMiguel Ojeda /// ``` 2099753dece8SMiguel Ojeda /// // Allocate vector big enough for 10 elements. 2100753dece8SMiguel Ojeda /// let mut v = Vec::with_capacity(10); 2101753dece8SMiguel Ojeda /// 2102753dece8SMiguel Ojeda /// // Fill in the first 3 elements. 2103753dece8SMiguel Ojeda /// let uninit = v.spare_capacity_mut(); 2104753dece8SMiguel Ojeda /// uninit[0].write(0); 2105753dece8SMiguel Ojeda /// uninit[1].write(1); 2106753dece8SMiguel Ojeda /// uninit[2].write(2); 2107753dece8SMiguel Ojeda /// 2108753dece8SMiguel Ojeda /// // Mark the first 3 elements of the vector as being initialized. 2109753dece8SMiguel Ojeda /// unsafe { 2110753dece8SMiguel Ojeda /// v.set_len(3); 2111753dece8SMiguel Ojeda /// } 2112753dece8SMiguel Ojeda /// 2113753dece8SMiguel Ojeda /// assert_eq!(&v, &[0, 1, 2]); 2114753dece8SMiguel Ojeda /// ``` 2115753dece8SMiguel Ojeda #[stable(feature = "vec_spare_capacity", since = "1.60.0")] 2116753dece8SMiguel Ojeda #[inline] 2117753dece8SMiguel Ojeda pub fn spare_capacity_mut(&mut self) -> &mut [MaybeUninit<T>] { 2118753dece8SMiguel Ojeda // Note: 2119753dece8SMiguel Ojeda // This method is not implemented in terms of `split_at_spare_mut`, 2120753dece8SMiguel Ojeda // to prevent invalidation of pointers to the buffer. 2121753dece8SMiguel Ojeda unsafe { 2122753dece8SMiguel Ojeda slice::from_raw_parts_mut( 2123753dece8SMiguel Ojeda self.as_mut_ptr().add(self.len) as *mut MaybeUninit<T>, 2124753dece8SMiguel Ojeda self.buf.capacity() - self.len, 2125753dece8SMiguel Ojeda ) 2126753dece8SMiguel Ojeda } 2127753dece8SMiguel Ojeda } 2128753dece8SMiguel Ojeda 2129753dece8SMiguel Ojeda /// Returns vector content as a slice of `T`, along with the remaining spare 2130753dece8SMiguel Ojeda /// capacity of the vector as a slice of `MaybeUninit<T>`. 2131753dece8SMiguel Ojeda /// 2132753dece8SMiguel Ojeda /// The returned spare capacity slice can be used to fill the vector with data 2133753dece8SMiguel Ojeda /// (e.g. by reading from a file) before marking the data as initialized using 2134753dece8SMiguel Ojeda /// the [`set_len`] method. 2135753dece8SMiguel Ojeda /// 2136753dece8SMiguel Ojeda /// [`set_len`]: Vec::set_len 2137753dece8SMiguel Ojeda /// 2138753dece8SMiguel Ojeda /// Note that this is a low-level API, which should be used with care for 2139753dece8SMiguel Ojeda /// optimization purposes. If you need to append data to a `Vec` 2140753dece8SMiguel Ojeda /// you can use [`push`], [`extend`], [`extend_from_slice`], 2141753dece8SMiguel Ojeda /// [`extend_from_within`], [`insert`], [`append`], [`resize`] or 2142753dece8SMiguel Ojeda /// [`resize_with`], depending on your exact needs. 2143753dece8SMiguel Ojeda /// 2144753dece8SMiguel Ojeda /// [`push`]: Vec::push 2145753dece8SMiguel Ojeda /// [`extend`]: Vec::extend 2146753dece8SMiguel Ojeda /// [`extend_from_slice`]: Vec::extend_from_slice 2147753dece8SMiguel Ojeda /// [`extend_from_within`]: Vec::extend_from_within 2148753dece8SMiguel Ojeda /// [`insert`]: Vec::insert 2149753dece8SMiguel Ojeda /// [`append`]: Vec::append 2150753dece8SMiguel Ojeda /// [`resize`]: Vec::resize 2151753dece8SMiguel Ojeda /// [`resize_with`]: Vec::resize_with 2152753dece8SMiguel Ojeda /// 2153753dece8SMiguel Ojeda /// # Examples 2154753dece8SMiguel Ojeda /// 2155753dece8SMiguel Ojeda /// ``` 2156753dece8SMiguel Ojeda /// #![feature(vec_split_at_spare)] 2157753dece8SMiguel Ojeda /// 2158753dece8SMiguel Ojeda /// let mut v = vec![1, 1, 2]; 2159753dece8SMiguel Ojeda /// 2160753dece8SMiguel Ojeda /// // Reserve additional space big enough for 10 elements. 2161753dece8SMiguel Ojeda /// v.reserve(10); 2162753dece8SMiguel Ojeda /// 2163753dece8SMiguel Ojeda /// let (init, uninit) = v.split_at_spare_mut(); 2164753dece8SMiguel Ojeda /// let sum = init.iter().copied().sum::<u32>(); 2165753dece8SMiguel Ojeda /// 2166753dece8SMiguel Ojeda /// // Fill in the next 4 elements. 2167753dece8SMiguel Ojeda /// uninit[0].write(sum); 2168753dece8SMiguel Ojeda /// uninit[1].write(sum * 2); 2169753dece8SMiguel Ojeda /// uninit[2].write(sum * 3); 2170753dece8SMiguel Ojeda /// uninit[3].write(sum * 4); 2171753dece8SMiguel Ojeda /// 2172753dece8SMiguel Ojeda /// // Mark the 4 elements of the vector as being initialized. 2173753dece8SMiguel Ojeda /// unsafe { 2174753dece8SMiguel Ojeda /// let len = v.len(); 2175753dece8SMiguel Ojeda /// v.set_len(len + 4); 2176753dece8SMiguel Ojeda /// } 2177753dece8SMiguel Ojeda /// 2178753dece8SMiguel Ojeda /// assert_eq!(&v, &[1, 1, 2, 4, 8, 12, 16]); 2179753dece8SMiguel Ojeda /// ``` 2180753dece8SMiguel Ojeda #[unstable(feature = "vec_split_at_spare", issue = "81944")] 2181753dece8SMiguel Ojeda #[inline] 2182753dece8SMiguel Ojeda pub fn split_at_spare_mut(&mut self) -> (&mut [T], &mut [MaybeUninit<T>]) { 2183753dece8SMiguel Ojeda // SAFETY: 2184753dece8SMiguel Ojeda // - len is ignored and so never changed 2185753dece8SMiguel Ojeda let (init, spare, _) = unsafe { self.split_at_spare_mut_with_len() }; 2186753dece8SMiguel Ojeda (init, spare) 2187753dece8SMiguel Ojeda } 2188753dece8SMiguel Ojeda 2189753dece8SMiguel Ojeda /// Safety: changing returned .2 (&mut usize) is considered the same as calling `.set_len(_)`. 2190753dece8SMiguel Ojeda /// 2191753dece8SMiguel Ojeda /// This method provides unique access to all vec parts at once in `extend_from_within`. 2192753dece8SMiguel Ojeda unsafe fn split_at_spare_mut_with_len( 2193753dece8SMiguel Ojeda &mut self, 2194753dece8SMiguel Ojeda ) -> (&mut [T], &mut [MaybeUninit<T>], &mut usize) { 2195753dece8SMiguel Ojeda let ptr = self.as_mut_ptr(); 2196753dece8SMiguel Ojeda // SAFETY: 2197753dece8SMiguel Ojeda // - `ptr` is guaranteed to be valid for `self.len` elements 2198753dece8SMiguel Ojeda // - but the allocation extends out to `self.buf.capacity()` elements, possibly 2199753dece8SMiguel Ojeda // uninitialized 2200753dece8SMiguel Ojeda let spare_ptr = unsafe { ptr.add(self.len) }; 2201753dece8SMiguel Ojeda let spare_ptr = spare_ptr.cast::<MaybeUninit<T>>(); 2202753dece8SMiguel Ojeda let spare_len = self.buf.capacity() - self.len; 2203753dece8SMiguel Ojeda 2204753dece8SMiguel Ojeda // SAFETY: 2205753dece8SMiguel Ojeda // - `ptr` is guaranteed to be valid for `self.len` elements 2206753dece8SMiguel Ojeda // - `spare_ptr` is pointing one element past the buffer, so it doesn't overlap with `initialized` 2207753dece8SMiguel Ojeda unsafe { 2208753dece8SMiguel Ojeda let initialized = slice::from_raw_parts_mut(ptr, self.len); 2209753dece8SMiguel Ojeda let spare = slice::from_raw_parts_mut(spare_ptr, spare_len); 2210753dece8SMiguel Ojeda 2211753dece8SMiguel Ojeda (initialized, spare, &mut self.len) 2212753dece8SMiguel Ojeda } 2213753dece8SMiguel Ojeda } 2214753dece8SMiguel Ojeda } 2215753dece8SMiguel Ojeda 2216753dece8SMiguel Ojeda impl<T: Clone, A: Allocator> Vec<T, A> { 2217753dece8SMiguel Ojeda /// Resizes the `Vec` in-place so that `len` is equal to `new_len`. 2218753dece8SMiguel Ojeda /// 2219753dece8SMiguel Ojeda /// If `new_len` is greater than `len`, the `Vec` is extended by the 2220753dece8SMiguel Ojeda /// difference, with each additional slot filled with `value`. 2221753dece8SMiguel Ojeda /// If `new_len` is less than `len`, the `Vec` is simply truncated. 2222753dece8SMiguel Ojeda /// 2223753dece8SMiguel Ojeda /// This method requires `T` to implement [`Clone`], 2224753dece8SMiguel Ojeda /// in order to be able to clone the passed value. 2225753dece8SMiguel Ojeda /// If you need more flexibility (or want to rely on [`Default`] instead of 2226753dece8SMiguel Ojeda /// [`Clone`]), use [`Vec::resize_with`]. 2227753dece8SMiguel Ojeda /// If you only need to resize to a smaller size, use [`Vec::truncate`]. 2228753dece8SMiguel Ojeda /// 2229753dece8SMiguel Ojeda /// # Examples 2230753dece8SMiguel Ojeda /// 2231753dece8SMiguel Ojeda /// ``` 2232753dece8SMiguel Ojeda /// let mut vec = vec!["hello"]; 2233753dece8SMiguel Ojeda /// vec.resize(3, "world"); 2234753dece8SMiguel Ojeda /// assert_eq!(vec, ["hello", "world", "world"]); 2235753dece8SMiguel Ojeda /// 2236753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 3, 4]; 2237753dece8SMiguel Ojeda /// vec.resize(2, 0); 2238753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2]); 2239753dece8SMiguel Ojeda /// ``` 2240753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2241753dece8SMiguel Ojeda #[stable(feature = "vec_resize", since = "1.5.0")] 2242753dece8SMiguel Ojeda pub fn resize(&mut self, new_len: usize, value: T) { 2243753dece8SMiguel Ojeda let len = self.len(); 2244753dece8SMiguel Ojeda 2245753dece8SMiguel Ojeda if new_len > len { 2246753dece8SMiguel Ojeda self.extend_with(new_len - len, ExtendElement(value)) 2247753dece8SMiguel Ojeda } else { 2248753dece8SMiguel Ojeda self.truncate(new_len); 2249753dece8SMiguel Ojeda } 2250753dece8SMiguel Ojeda } 2251753dece8SMiguel Ojeda 2252753dece8SMiguel Ojeda /// Clones and appends all elements in a slice to the `Vec`. 2253753dece8SMiguel Ojeda /// 2254753dece8SMiguel Ojeda /// Iterates over the slice `other`, clones each element, and then appends 2255753dece8SMiguel Ojeda /// it to this `Vec`. The `other` slice is traversed in-order. 2256753dece8SMiguel Ojeda /// 2257753dece8SMiguel Ojeda /// Note that this function is same as [`extend`] except that it is 2258753dece8SMiguel Ojeda /// specialized to work with slices instead. If and when Rust gets 2259753dece8SMiguel Ojeda /// specialization this function will likely be deprecated (but still 2260753dece8SMiguel Ojeda /// available). 2261753dece8SMiguel Ojeda /// 2262753dece8SMiguel Ojeda /// # Examples 2263753dece8SMiguel Ojeda /// 2264753dece8SMiguel Ojeda /// ``` 2265753dece8SMiguel Ojeda /// let mut vec = vec![1]; 2266753dece8SMiguel Ojeda /// vec.extend_from_slice(&[2, 3, 4]); 2267753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2, 3, 4]); 2268753dece8SMiguel Ojeda /// ``` 2269753dece8SMiguel Ojeda /// 2270753dece8SMiguel Ojeda /// [`extend`]: Vec::extend 2271753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2272753dece8SMiguel Ojeda #[stable(feature = "vec_extend_from_slice", since = "1.6.0")] 2273753dece8SMiguel Ojeda pub fn extend_from_slice(&mut self, other: &[T]) { 2274753dece8SMiguel Ojeda self.spec_extend(other.iter()) 2275753dece8SMiguel Ojeda } 2276753dece8SMiguel Ojeda 2277753dece8SMiguel Ojeda /// Copies elements from `src` range to the end of the vector. 2278753dece8SMiguel Ojeda /// 2279753dece8SMiguel Ojeda /// # Panics 2280753dece8SMiguel Ojeda /// 2281753dece8SMiguel Ojeda /// Panics if the starting point is greater than the end point or if 2282753dece8SMiguel Ojeda /// the end point is greater than the length of the vector. 2283753dece8SMiguel Ojeda /// 2284753dece8SMiguel Ojeda /// # Examples 2285753dece8SMiguel Ojeda /// 2286753dece8SMiguel Ojeda /// ``` 2287753dece8SMiguel Ojeda /// let mut vec = vec![0, 1, 2, 3, 4]; 2288753dece8SMiguel Ojeda /// 2289753dece8SMiguel Ojeda /// vec.extend_from_within(2..); 2290753dece8SMiguel Ojeda /// assert_eq!(vec, [0, 1, 2, 3, 4, 2, 3, 4]); 2291753dece8SMiguel Ojeda /// 2292753dece8SMiguel Ojeda /// vec.extend_from_within(..2); 2293753dece8SMiguel Ojeda /// assert_eq!(vec, [0, 1, 2, 3, 4, 2, 3, 4, 0, 1]); 2294753dece8SMiguel Ojeda /// 2295753dece8SMiguel Ojeda /// vec.extend_from_within(4..8); 2296753dece8SMiguel Ojeda /// assert_eq!(vec, [0, 1, 2, 3, 4, 2, 3, 4, 0, 1, 4, 2, 3, 4]); 2297753dece8SMiguel Ojeda /// ``` 2298753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2299753dece8SMiguel Ojeda #[stable(feature = "vec_extend_from_within", since = "1.53.0")] 2300753dece8SMiguel Ojeda pub fn extend_from_within<R>(&mut self, src: R) 2301753dece8SMiguel Ojeda where 2302753dece8SMiguel Ojeda R: RangeBounds<usize>, 2303753dece8SMiguel Ojeda { 2304753dece8SMiguel Ojeda let range = slice::range(src, ..self.len()); 2305753dece8SMiguel Ojeda self.reserve(range.len()); 2306753dece8SMiguel Ojeda 2307753dece8SMiguel Ojeda // SAFETY: 2308753dece8SMiguel Ojeda // - `slice::range` guarantees that the given range is valid for indexing self 2309753dece8SMiguel Ojeda unsafe { 2310753dece8SMiguel Ojeda self.spec_extend_from_within(range); 2311753dece8SMiguel Ojeda } 2312753dece8SMiguel Ojeda } 2313753dece8SMiguel Ojeda } 2314753dece8SMiguel Ojeda 2315753dece8SMiguel Ojeda impl<T, A: Allocator, const N: usize> Vec<[T; N], A> { 2316753dece8SMiguel Ojeda /// Takes a `Vec<[T; N]>` and flattens it into a `Vec<T>`. 2317753dece8SMiguel Ojeda /// 2318753dece8SMiguel Ojeda /// # Panics 2319753dece8SMiguel Ojeda /// 2320753dece8SMiguel Ojeda /// Panics if the length of the resulting vector would overflow a `usize`. 2321753dece8SMiguel Ojeda /// 2322753dece8SMiguel Ojeda /// This is only possible when flattening a vector of arrays of zero-sized 2323753dece8SMiguel Ojeda /// types, and thus tends to be irrelevant in practice. If 2324753dece8SMiguel Ojeda /// `size_of::<T>() > 0`, this will never panic. 2325753dece8SMiguel Ojeda /// 2326753dece8SMiguel Ojeda /// # Examples 2327753dece8SMiguel Ojeda /// 2328753dece8SMiguel Ojeda /// ``` 2329753dece8SMiguel Ojeda /// #![feature(slice_flatten)] 2330753dece8SMiguel Ojeda /// 2331753dece8SMiguel Ojeda /// let mut vec = vec![[1, 2, 3], [4, 5, 6], [7, 8, 9]]; 2332753dece8SMiguel Ojeda /// assert_eq!(vec.pop(), Some([7, 8, 9])); 2333753dece8SMiguel Ojeda /// 2334753dece8SMiguel Ojeda /// let mut flattened = vec.into_flattened(); 2335753dece8SMiguel Ojeda /// assert_eq!(flattened.pop(), Some(6)); 2336753dece8SMiguel Ojeda /// ``` 2337753dece8SMiguel Ojeda #[unstable(feature = "slice_flatten", issue = "95629")] 2338753dece8SMiguel Ojeda pub fn into_flattened(self) -> Vec<T, A> { 2339753dece8SMiguel Ojeda let (ptr, len, cap, alloc) = self.into_raw_parts_with_alloc(); 2340753dece8SMiguel Ojeda let (new_len, new_cap) = if mem::size_of::<T>() == 0 { 2341753dece8SMiguel Ojeda (len.checked_mul(N).expect("vec len overflow"), usize::MAX) 2342753dece8SMiguel Ojeda } else { 2343753dece8SMiguel Ojeda // SAFETY: 2344753dece8SMiguel Ojeda // - `cap * N` cannot overflow because the allocation is already in 2345753dece8SMiguel Ojeda // the address space. 2346753dece8SMiguel Ojeda // - Each `[T; N]` has `N` valid elements, so there are `len * N` 2347753dece8SMiguel Ojeda // valid elements in the allocation. 2348753dece8SMiguel Ojeda unsafe { (len.unchecked_mul(N), cap.unchecked_mul(N)) } 2349753dece8SMiguel Ojeda }; 2350753dece8SMiguel Ojeda // SAFETY: 2351753dece8SMiguel Ojeda // - `ptr` was allocated by `self` 2352753dece8SMiguel Ojeda // - `ptr` is well-aligned because `[T; N]` has the same alignment as `T`. 2353753dece8SMiguel Ojeda // - `new_cap` refers to the same sized allocation as `cap` because 2354753dece8SMiguel Ojeda // `new_cap * size_of::<T>()` == `cap * size_of::<[T; N]>()` 2355753dece8SMiguel Ojeda // - `len` <= `cap`, so `len * N` <= `cap * N`. 2356753dece8SMiguel Ojeda unsafe { Vec::<T, A>::from_raw_parts_in(ptr.cast(), new_len, new_cap, alloc) } 2357753dece8SMiguel Ojeda } 2358753dece8SMiguel Ojeda } 2359753dece8SMiguel Ojeda 2360753dece8SMiguel Ojeda // This code generalizes `extend_with_{element,default}`. 2361753dece8SMiguel Ojeda trait ExtendWith<T> { 2362753dece8SMiguel Ojeda fn next(&mut self) -> T; 2363753dece8SMiguel Ojeda fn last(self) -> T; 2364753dece8SMiguel Ojeda } 2365753dece8SMiguel Ojeda 2366753dece8SMiguel Ojeda struct ExtendElement<T>(T); 2367753dece8SMiguel Ojeda impl<T: Clone> ExtendWith<T> for ExtendElement<T> { 2368753dece8SMiguel Ojeda fn next(&mut self) -> T { 2369753dece8SMiguel Ojeda self.0.clone() 2370753dece8SMiguel Ojeda } 2371753dece8SMiguel Ojeda fn last(self) -> T { 2372753dece8SMiguel Ojeda self.0 2373753dece8SMiguel Ojeda } 2374753dece8SMiguel Ojeda } 2375753dece8SMiguel Ojeda 2376753dece8SMiguel Ojeda struct ExtendFunc<F>(F); 2377753dece8SMiguel Ojeda impl<T, F: FnMut() -> T> ExtendWith<T> for ExtendFunc<F> { 2378753dece8SMiguel Ojeda fn next(&mut self) -> T { 2379753dece8SMiguel Ojeda (self.0)() 2380753dece8SMiguel Ojeda } 2381753dece8SMiguel Ojeda fn last(mut self) -> T { 2382753dece8SMiguel Ojeda (self.0)() 2383753dece8SMiguel Ojeda } 2384753dece8SMiguel Ojeda } 2385753dece8SMiguel Ojeda 2386753dece8SMiguel Ojeda impl<T, A: Allocator> Vec<T, A> { 2387753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2388753dece8SMiguel Ojeda /// Extend the vector by `n` values, using the given generator. 2389753dece8SMiguel Ojeda fn extend_with<E: ExtendWith<T>>(&mut self, n: usize, mut value: E) { 2390753dece8SMiguel Ojeda self.reserve(n); 2391753dece8SMiguel Ojeda 2392753dece8SMiguel Ojeda unsafe { 2393753dece8SMiguel Ojeda let mut ptr = self.as_mut_ptr().add(self.len()); 2394753dece8SMiguel Ojeda // Use SetLenOnDrop to work around bug where compiler 2395753dece8SMiguel Ojeda // might not realize the store through `ptr` through self.set_len() 2396753dece8SMiguel Ojeda // don't alias. 2397753dece8SMiguel Ojeda let mut local_len = SetLenOnDrop::new(&mut self.len); 2398753dece8SMiguel Ojeda 2399753dece8SMiguel Ojeda // Write all elements except the last one 2400753dece8SMiguel Ojeda for _ in 1..n { 2401753dece8SMiguel Ojeda ptr::write(ptr, value.next()); 2402753dece8SMiguel Ojeda ptr = ptr.offset(1); 2403753dece8SMiguel Ojeda // Increment the length in every step in case next() panics 2404753dece8SMiguel Ojeda local_len.increment_len(1); 2405753dece8SMiguel Ojeda } 2406753dece8SMiguel Ojeda 2407753dece8SMiguel Ojeda if n > 0 { 2408753dece8SMiguel Ojeda // We can write the last element directly without cloning needlessly 2409753dece8SMiguel Ojeda ptr::write(ptr, value.last()); 2410753dece8SMiguel Ojeda local_len.increment_len(1); 2411753dece8SMiguel Ojeda } 2412753dece8SMiguel Ojeda 2413753dece8SMiguel Ojeda // len set by scope guard 2414753dece8SMiguel Ojeda } 2415753dece8SMiguel Ojeda } 2416753dece8SMiguel Ojeda } 2417753dece8SMiguel Ojeda 2418753dece8SMiguel Ojeda impl<T: PartialEq, A: Allocator> Vec<T, A> { 2419753dece8SMiguel Ojeda /// Removes consecutive repeated elements in the vector according to the 2420753dece8SMiguel Ojeda /// [`PartialEq`] trait implementation. 2421753dece8SMiguel Ojeda /// 2422753dece8SMiguel Ojeda /// If the vector is sorted, this removes all duplicates. 2423753dece8SMiguel Ojeda /// 2424753dece8SMiguel Ojeda /// # Examples 2425753dece8SMiguel Ojeda /// 2426753dece8SMiguel Ojeda /// ``` 2427753dece8SMiguel Ojeda /// let mut vec = vec![1, 2, 2, 3, 2]; 2428753dece8SMiguel Ojeda /// 2429753dece8SMiguel Ojeda /// vec.dedup(); 2430753dece8SMiguel Ojeda /// 2431753dece8SMiguel Ojeda /// assert_eq!(vec, [1, 2, 3, 2]); 2432753dece8SMiguel Ojeda /// ``` 2433753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2434753dece8SMiguel Ojeda #[inline] 2435753dece8SMiguel Ojeda pub fn dedup(&mut self) { 2436753dece8SMiguel Ojeda self.dedup_by(|a, b| a == b) 2437753dece8SMiguel Ojeda } 2438753dece8SMiguel Ojeda } 2439753dece8SMiguel Ojeda 2440753dece8SMiguel Ojeda //////////////////////////////////////////////////////////////////////////////// 2441753dece8SMiguel Ojeda // Internal methods and functions 2442753dece8SMiguel Ojeda //////////////////////////////////////////////////////////////////////////////// 2443753dece8SMiguel Ojeda 2444753dece8SMiguel Ojeda #[doc(hidden)] 2445753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2446753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2447753dece8SMiguel Ojeda pub fn from_elem<T: Clone>(elem: T, n: usize) -> Vec<T> { 2448753dece8SMiguel Ojeda <T as SpecFromElem>::from_elem(elem, n, Global) 2449753dece8SMiguel Ojeda } 2450753dece8SMiguel Ojeda 2451753dece8SMiguel Ojeda #[doc(hidden)] 2452753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2453753dece8SMiguel Ojeda #[unstable(feature = "allocator_api", issue = "32838")] 2454753dece8SMiguel Ojeda pub fn from_elem_in<T: Clone, A: Allocator>(elem: T, n: usize, alloc: A) -> Vec<T, A> { 2455753dece8SMiguel Ojeda <T as SpecFromElem>::from_elem(elem, n, alloc) 2456753dece8SMiguel Ojeda } 2457753dece8SMiguel Ojeda 2458753dece8SMiguel Ojeda trait ExtendFromWithinSpec { 2459753dece8SMiguel Ojeda /// # Safety 2460753dece8SMiguel Ojeda /// 2461753dece8SMiguel Ojeda /// - `src` needs to be valid index 2462753dece8SMiguel Ojeda /// - `self.capacity() - self.len()` must be `>= src.len()` 2463753dece8SMiguel Ojeda unsafe fn spec_extend_from_within(&mut self, src: Range<usize>); 2464753dece8SMiguel Ojeda } 2465753dece8SMiguel Ojeda 2466753dece8SMiguel Ojeda impl<T: Clone, A: Allocator> ExtendFromWithinSpec for Vec<T, A> { 2467753dece8SMiguel Ojeda default unsafe fn spec_extend_from_within(&mut self, src: Range<usize>) { 2468753dece8SMiguel Ojeda // SAFETY: 2469753dece8SMiguel Ojeda // - len is increased only after initializing elements 2470753dece8SMiguel Ojeda let (this, spare, len) = unsafe { self.split_at_spare_mut_with_len() }; 2471753dece8SMiguel Ojeda 2472753dece8SMiguel Ojeda // SAFETY: 2473753dece8SMiguel Ojeda // - caller guaratees that src is a valid index 2474753dece8SMiguel Ojeda let to_clone = unsafe { this.get_unchecked(src) }; 2475753dece8SMiguel Ojeda 2476753dece8SMiguel Ojeda iter::zip(to_clone, spare) 2477753dece8SMiguel Ojeda .map(|(src, dst)| dst.write(src.clone())) 2478753dece8SMiguel Ojeda // Note: 2479753dece8SMiguel Ojeda // - Element was just initialized with `MaybeUninit::write`, so it's ok to increase len 2480753dece8SMiguel Ojeda // - len is increased after each element to prevent leaks (see issue #82533) 2481753dece8SMiguel Ojeda .for_each(|_| *len += 1); 2482753dece8SMiguel Ojeda } 2483753dece8SMiguel Ojeda } 2484753dece8SMiguel Ojeda 2485753dece8SMiguel Ojeda impl<T: Copy, A: Allocator> ExtendFromWithinSpec for Vec<T, A> { 2486753dece8SMiguel Ojeda unsafe fn spec_extend_from_within(&mut self, src: Range<usize>) { 2487753dece8SMiguel Ojeda let count = src.len(); 2488753dece8SMiguel Ojeda { 2489753dece8SMiguel Ojeda let (init, spare) = self.split_at_spare_mut(); 2490753dece8SMiguel Ojeda 2491753dece8SMiguel Ojeda // SAFETY: 2492753dece8SMiguel Ojeda // - caller guaratees that `src` is a valid index 2493753dece8SMiguel Ojeda let source = unsafe { init.get_unchecked(src) }; 2494753dece8SMiguel Ojeda 2495753dece8SMiguel Ojeda // SAFETY: 2496753dece8SMiguel Ojeda // - Both pointers are created from unique slice references (`&mut [_]`) 2497753dece8SMiguel Ojeda // so they are valid and do not overlap. 2498753dece8SMiguel Ojeda // - Elements are :Copy so it's OK to to copy them, without doing 2499753dece8SMiguel Ojeda // anything with the original values 2500753dece8SMiguel Ojeda // - `count` is equal to the len of `source`, so source is valid for 2501753dece8SMiguel Ojeda // `count` reads 2502753dece8SMiguel Ojeda // - `.reserve(count)` guarantees that `spare.len() >= count` so spare 2503753dece8SMiguel Ojeda // is valid for `count` writes 2504753dece8SMiguel Ojeda unsafe { ptr::copy_nonoverlapping(source.as_ptr(), spare.as_mut_ptr() as _, count) }; 2505753dece8SMiguel Ojeda } 2506753dece8SMiguel Ojeda 2507753dece8SMiguel Ojeda // SAFETY: 2508753dece8SMiguel Ojeda // - The elements were just initialized by `copy_nonoverlapping` 2509753dece8SMiguel Ojeda self.len += count; 2510753dece8SMiguel Ojeda } 2511753dece8SMiguel Ojeda } 2512753dece8SMiguel Ojeda 2513753dece8SMiguel Ojeda //////////////////////////////////////////////////////////////////////////////// 2514753dece8SMiguel Ojeda // Common trait implementations for Vec 2515753dece8SMiguel Ojeda //////////////////////////////////////////////////////////////////////////////// 2516753dece8SMiguel Ojeda 2517753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2518753dece8SMiguel Ojeda impl<T, A: Allocator> ops::Deref for Vec<T, A> { 2519753dece8SMiguel Ojeda type Target = [T]; 2520753dece8SMiguel Ojeda 2521753dece8SMiguel Ojeda fn deref(&self) -> &[T] { 2522753dece8SMiguel Ojeda unsafe { slice::from_raw_parts(self.as_ptr(), self.len) } 2523753dece8SMiguel Ojeda } 2524753dece8SMiguel Ojeda } 2525753dece8SMiguel Ojeda 2526753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2527753dece8SMiguel Ojeda impl<T, A: Allocator> ops::DerefMut for Vec<T, A> { 2528753dece8SMiguel Ojeda fn deref_mut(&mut self) -> &mut [T] { 2529753dece8SMiguel Ojeda unsafe { slice::from_raw_parts_mut(self.as_mut_ptr(), self.len) } 2530753dece8SMiguel Ojeda } 2531753dece8SMiguel Ojeda } 2532753dece8SMiguel Ojeda 2533753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2534753dece8SMiguel Ojeda trait SpecCloneFrom { 2535753dece8SMiguel Ojeda fn clone_from(this: &mut Self, other: &Self); 2536753dece8SMiguel Ojeda } 2537753dece8SMiguel Ojeda 2538753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2539753dece8SMiguel Ojeda impl<T: Clone, A: Allocator> SpecCloneFrom for Vec<T, A> { 2540753dece8SMiguel Ojeda default fn clone_from(this: &mut Self, other: &Self) { 2541753dece8SMiguel Ojeda // drop anything that will not be overwritten 2542753dece8SMiguel Ojeda this.truncate(other.len()); 2543753dece8SMiguel Ojeda 2544753dece8SMiguel Ojeda // self.len <= other.len due to the truncate above, so the 2545753dece8SMiguel Ojeda // slices here are always in-bounds. 2546753dece8SMiguel Ojeda let (init, tail) = other.split_at(this.len()); 2547753dece8SMiguel Ojeda 2548753dece8SMiguel Ojeda // reuse the contained values' allocations/resources. 2549753dece8SMiguel Ojeda this.clone_from_slice(init); 2550753dece8SMiguel Ojeda this.extend_from_slice(tail); 2551753dece8SMiguel Ojeda } 2552753dece8SMiguel Ojeda } 2553753dece8SMiguel Ojeda 2554753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2555753dece8SMiguel Ojeda impl<T: Copy, A: Allocator> SpecCloneFrom for Vec<T, A> { 2556753dece8SMiguel Ojeda fn clone_from(this: &mut Self, other: &Self) { 2557753dece8SMiguel Ojeda this.clear(); 2558753dece8SMiguel Ojeda this.extend_from_slice(other); 2559753dece8SMiguel Ojeda } 2560753dece8SMiguel Ojeda } 2561753dece8SMiguel Ojeda 2562753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2563753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2564753dece8SMiguel Ojeda impl<T: Clone, A: Allocator + Clone> Clone for Vec<T, A> { 2565753dece8SMiguel Ojeda #[cfg(not(test))] 2566753dece8SMiguel Ojeda fn clone(&self) -> Self { 2567753dece8SMiguel Ojeda let alloc = self.allocator().clone(); 2568753dece8SMiguel Ojeda <[T]>::to_vec_in(&**self, alloc) 2569753dece8SMiguel Ojeda } 2570753dece8SMiguel Ojeda 2571753dece8SMiguel Ojeda // HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is 2572753dece8SMiguel Ojeda // required for this method definition, is not available. Instead use the 2573753dece8SMiguel Ojeda // `slice::to_vec` function which is only available with cfg(test) 2574753dece8SMiguel Ojeda // NB see the slice::hack module in slice.rs for more information 2575753dece8SMiguel Ojeda #[cfg(test)] 2576753dece8SMiguel Ojeda fn clone(&self) -> Self { 2577753dece8SMiguel Ojeda let alloc = self.allocator().clone(); 2578753dece8SMiguel Ojeda crate::slice::to_vec(&**self, alloc) 2579753dece8SMiguel Ojeda } 2580753dece8SMiguel Ojeda 2581753dece8SMiguel Ojeda fn clone_from(&mut self, other: &Self) { 2582753dece8SMiguel Ojeda SpecCloneFrom::clone_from(self, other) 2583753dece8SMiguel Ojeda } 2584753dece8SMiguel Ojeda } 2585753dece8SMiguel Ojeda 2586753dece8SMiguel Ojeda /// The hash of a vector is the same as that of the corresponding slice, 2587753dece8SMiguel Ojeda /// as required by the `core::borrow::Borrow` implementation. 2588753dece8SMiguel Ojeda /// 2589753dece8SMiguel Ojeda /// ``` 2590753dece8SMiguel Ojeda /// #![feature(build_hasher_simple_hash_one)] 2591753dece8SMiguel Ojeda /// use std::hash::BuildHasher; 2592753dece8SMiguel Ojeda /// 2593753dece8SMiguel Ojeda /// let b = std::collections::hash_map::RandomState::new(); 2594753dece8SMiguel Ojeda /// let v: Vec<u8> = vec![0xa8, 0x3c, 0x09]; 2595753dece8SMiguel Ojeda /// let s: &[u8] = &[0xa8, 0x3c, 0x09]; 2596753dece8SMiguel Ojeda /// assert_eq!(b.hash_one(v), b.hash_one(s)); 2597753dece8SMiguel Ojeda /// ``` 2598753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2599753dece8SMiguel Ojeda impl<T: Hash, A: Allocator> Hash for Vec<T, A> { 2600753dece8SMiguel Ojeda #[inline] 2601753dece8SMiguel Ojeda fn hash<H: Hasher>(&self, state: &mut H) { 2602753dece8SMiguel Ojeda Hash::hash(&**self, state) 2603753dece8SMiguel Ojeda } 2604753dece8SMiguel Ojeda } 2605753dece8SMiguel Ojeda 2606753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2607753dece8SMiguel Ojeda #[rustc_on_unimplemented( 2608753dece8SMiguel Ojeda message = "vector indices are of type `usize` or ranges of `usize`", 2609753dece8SMiguel Ojeda label = "vector indices are of type `usize` or ranges of `usize`" 2610753dece8SMiguel Ojeda )] 2611753dece8SMiguel Ojeda impl<T, I: SliceIndex<[T]>, A: Allocator> Index<I> for Vec<T, A> { 2612753dece8SMiguel Ojeda type Output = I::Output; 2613753dece8SMiguel Ojeda 2614753dece8SMiguel Ojeda #[inline] 2615753dece8SMiguel Ojeda fn index(&self, index: I) -> &Self::Output { 2616753dece8SMiguel Ojeda Index::index(&**self, index) 2617753dece8SMiguel Ojeda } 2618753dece8SMiguel Ojeda } 2619753dece8SMiguel Ojeda 2620753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2621753dece8SMiguel Ojeda #[rustc_on_unimplemented( 2622753dece8SMiguel Ojeda message = "vector indices are of type `usize` or ranges of `usize`", 2623753dece8SMiguel Ojeda label = "vector indices are of type `usize` or ranges of `usize`" 2624753dece8SMiguel Ojeda )] 2625753dece8SMiguel Ojeda impl<T, I: SliceIndex<[T]>, A: Allocator> IndexMut<I> for Vec<T, A> { 2626753dece8SMiguel Ojeda #[inline] 2627753dece8SMiguel Ojeda fn index_mut(&mut self, index: I) -> &mut Self::Output { 2628753dece8SMiguel Ojeda IndexMut::index_mut(&mut **self, index) 2629753dece8SMiguel Ojeda } 2630753dece8SMiguel Ojeda } 2631753dece8SMiguel Ojeda 2632753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2633753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2634753dece8SMiguel Ojeda impl<T> FromIterator<T> for Vec<T> { 2635753dece8SMiguel Ojeda #[inline] 2636753dece8SMiguel Ojeda fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Vec<T> { 2637753dece8SMiguel Ojeda <Self as SpecFromIter<T, I::IntoIter>>::from_iter(iter.into_iter()) 2638753dece8SMiguel Ojeda } 2639753dece8SMiguel Ojeda } 2640753dece8SMiguel Ojeda 2641753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2642753dece8SMiguel Ojeda impl<T, A: Allocator> IntoIterator for Vec<T, A> { 2643753dece8SMiguel Ojeda type Item = T; 2644753dece8SMiguel Ojeda type IntoIter = IntoIter<T, A>; 2645753dece8SMiguel Ojeda 2646753dece8SMiguel Ojeda /// Creates a consuming iterator, that is, one that moves each value out of 2647753dece8SMiguel Ojeda /// the vector (from start to end). The vector cannot be used after calling 2648753dece8SMiguel Ojeda /// this. 2649753dece8SMiguel Ojeda /// 2650753dece8SMiguel Ojeda /// # Examples 2651753dece8SMiguel Ojeda /// 2652753dece8SMiguel Ojeda /// ``` 2653753dece8SMiguel Ojeda /// let v = vec!["a".to_string(), "b".to_string()]; 2654753dece8SMiguel Ojeda /// for s in v.into_iter() { 2655753dece8SMiguel Ojeda /// // s has type String, not &String 2656753dece8SMiguel Ojeda /// println!("{s}"); 2657753dece8SMiguel Ojeda /// } 2658753dece8SMiguel Ojeda /// ``` 2659753dece8SMiguel Ojeda #[inline] 2660753dece8SMiguel Ojeda fn into_iter(self) -> IntoIter<T, A> { 2661753dece8SMiguel Ojeda unsafe { 2662753dece8SMiguel Ojeda let mut me = ManuallyDrop::new(self); 2663753dece8SMiguel Ojeda let alloc = ManuallyDrop::new(ptr::read(me.allocator())); 2664753dece8SMiguel Ojeda let begin = me.as_mut_ptr(); 2665753dece8SMiguel Ojeda let end = if mem::size_of::<T>() == 0 { 2666753dece8SMiguel Ojeda arith_offset(begin as *const i8, me.len() as isize) as *const T 2667753dece8SMiguel Ojeda } else { 2668753dece8SMiguel Ojeda begin.add(me.len()) as *const T 2669753dece8SMiguel Ojeda }; 2670753dece8SMiguel Ojeda let cap = me.buf.capacity(); 2671753dece8SMiguel Ojeda IntoIter { 2672753dece8SMiguel Ojeda buf: NonNull::new_unchecked(begin), 2673753dece8SMiguel Ojeda phantom: PhantomData, 2674753dece8SMiguel Ojeda cap, 2675753dece8SMiguel Ojeda alloc, 2676753dece8SMiguel Ojeda ptr: begin, 2677753dece8SMiguel Ojeda end, 2678753dece8SMiguel Ojeda } 2679753dece8SMiguel Ojeda } 2680753dece8SMiguel Ojeda } 2681753dece8SMiguel Ojeda } 2682753dece8SMiguel Ojeda 2683753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2684753dece8SMiguel Ojeda impl<'a, T, A: Allocator> IntoIterator for &'a Vec<T, A> { 2685753dece8SMiguel Ojeda type Item = &'a T; 2686753dece8SMiguel Ojeda type IntoIter = slice::Iter<'a, T>; 2687753dece8SMiguel Ojeda 2688753dece8SMiguel Ojeda fn into_iter(self) -> slice::Iter<'a, T> { 2689753dece8SMiguel Ojeda self.iter() 2690753dece8SMiguel Ojeda } 2691753dece8SMiguel Ojeda } 2692753dece8SMiguel Ojeda 2693753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2694753dece8SMiguel Ojeda impl<'a, T, A: Allocator> IntoIterator for &'a mut Vec<T, A> { 2695753dece8SMiguel Ojeda type Item = &'a mut T; 2696753dece8SMiguel Ojeda type IntoIter = slice::IterMut<'a, T>; 2697753dece8SMiguel Ojeda 2698753dece8SMiguel Ojeda fn into_iter(self) -> slice::IterMut<'a, T> { 2699753dece8SMiguel Ojeda self.iter_mut() 2700753dece8SMiguel Ojeda } 2701753dece8SMiguel Ojeda } 2702753dece8SMiguel Ojeda 2703753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2704753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2705753dece8SMiguel Ojeda impl<T, A: Allocator> Extend<T> for Vec<T, A> { 2706753dece8SMiguel Ojeda #[inline] 2707753dece8SMiguel Ojeda fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) { 2708753dece8SMiguel Ojeda <Self as SpecExtend<T, I::IntoIter>>::spec_extend(self, iter.into_iter()) 2709753dece8SMiguel Ojeda } 2710753dece8SMiguel Ojeda 2711753dece8SMiguel Ojeda #[inline] 2712753dece8SMiguel Ojeda fn extend_one(&mut self, item: T) { 2713753dece8SMiguel Ojeda self.push(item); 2714753dece8SMiguel Ojeda } 2715753dece8SMiguel Ojeda 2716753dece8SMiguel Ojeda #[inline] 2717753dece8SMiguel Ojeda fn extend_reserve(&mut self, additional: usize) { 2718753dece8SMiguel Ojeda self.reserve(additional); 2719753dece8SMiguel Ojeda } 2720753dece8SMiguel Ojeda } 2721753dece8SMiguel Ojeda 2722753dece8SMiguel Ojeda impl<T, A: Allocator> Vec<T, A> { 2723753dece8SMiguel Ojeda // leaf method to which various SpecFrom/SpecExtend implementations delegate when 2724753dece8SMiguel Ojeda // they have no further optimizations to apply 2725753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2726753dece8SMiguel Ojeda fn extend_desugared<I: Iterator<Item = T>>(&mut self, mut iterator: I) { 2727753dece8SMiguel Ojeda // This is the case for a general iterator. 2728753dece8SMiguel Ojeda // 2729753dece8SMiguel Ojeda // This function should be the moral equivalent of: 2730753dece8SMiguel Ojeda // 2731753dece8SMiguel Ojeda // for item in iterator { 2732753dece8SMiguel Ojeda // self.push(item); 2733753dece8SMiguel Ojeda // } 2734753dece8SMiguel Ojeda while let Some(element) = iterator.next() { 2735753dece8SMiguel Ojeda let len = self.len(); 2736753dece8SMiguel Ojeda if len == self.capacity() { 2737753dece8SMiguel Ojeda let (lower, _) = iterator.size_hint(); 2738753dece8SMiguel Ojeda self.reserve(lower.saturating_add(1)); 2739753dece8SMiguel Ojeda } 2740753dece8SMiguel Ojeda unsafe { 2741753dece8SMiguel Ojeda ptr::write(self.as_mut_ptr().add(len), element); 2742753dece8SMiguel Ojeda // Since next() executes user code which can panic we have to bump the length 2743753dece8SMiguel Ojeda // after each step. 2744753dece8SMiguel Ojeda // NB can't overflow since we would have had to alloc the address space 2745753dece8SMiguel Ojeda self.set_len(len + 1); 2746753dece8SMiguel Ojeda } 2747753dece8SMiguel Ojeda } 2748753dece8SMiguel Ojeda } 2749753dece8SMiguel Ojeda 2750753dece8SMiguel Ojeda /// Creates a splicing iterator that replaces the specified range in the vector 2751753dece8SMiguel Ojeda /// with the given `replace_with` iterator and yields the removed items. 2752753dece8SMiguel Ojeda /// `replace_with` does not need to be the same length as `range`. 2753753dece8SMiguel Ojeda /// 2754753dece8SMiguel Ojeda /// `range` is removed even if the iterator is not consumed until the end. 2755753dece8SMiguel Ojeda /// 2756753dece8SMiguel Ojeda /// It is unspecified how many elements are removed from the vector 2757753dece8SMiguel Ojeda /// if the `Splice` value is leaked. 2758753dece8SMiguel Ojeda /// 2759753dece8SMiguel Ojeda /// The input iterator `replace_with` is only consumed when the `Splice` value is dropped. 2760753dece8SMiguel Ojeda /// 2761753dece8SMiguel Ojeda /// This is optimal if: 2762753dece8SMiguel Ojeda /// 2763753dece8SMiguel Ojeda /// * The tail (elements in the vector after `range`) is empty, 2764753dece8SMiguel Ojeda /// * or `replace_with` yields fewer or equal elements than `range`’s length 2765753dece8SMiguel Ojeda /// * or the lower bound of its `size_hint()` is exact. 2766753dece8SMiguel Ojeda /// 2767753dece8SMiguel Ojeda /// Otherwise, a temporary vector is allocated and the tail is moved twice. 2768753dece8SMiguel Ojeda /// 2769753dece8SMiguel Ojeda /// # Panics 2770753dece8SMiguel Ojeda /// 2771753dece8SMiguel Ojeda /// Panics if the starting point is greater than the end point or if 2772753dece8SMiguel Ojeda /// the end point is greater than the length of the vector. 2773753dece8SMiguel Ojeda /// 2774753dece8SMiguel Ojeda /// # Examples 2775753dece8SMiguel Ojeda /// 2776753dece8SMiguel Ojeda /// ``` 2777753dece8SMiguel Ojeda /// let mut v = vec![1, 2, 3, 4]; 2778753dece8SMiguel Ojeda /// let new = [7, 8, 9]; 2779753dece8SMiguel Ojeda /// let u: Vec<_> = v.splice(1..3, new).collect(); 2780753dece8SMiguel Ojeda /// assert_eq!(v, &[1, 7, 8, 9, 4]); 2781753dece8SMiguel Ojeda /// assert_eq!(u, &[2, 3]); 2782753dece8SMiguel Ojeda /// ``` 2783753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2784753dece8SMiguel Ojeda #[inline] 2785753dece8SMiguel Ojeda #[stable(feature = "vec_splice", since = "1.21.0")] 2786753dece8SMiguel Ojeda pub fn splice<R, I>(&mut self, range: R, replace_with: I) -> Splice<'_, I::IntoIter, A> 2787753dece8SMiguel Ojeda where 2788753dece8SMiguel Ojeda R: RangeBounds<usize>, 2789753dece8SMiguel Ojeda I: IntoIterator<Item = T>, 2790753dece8SMiguel Ojeda { 2791753dece8SMiguel Ojeda Splice { drain: self.drain(range), replace_with: replace_with.into_iter() } 2792753dece8SMiguel Ojeda } 2793753dece8SMiguel Ojeda 2794753dece8SMiguel Ojeda /// Creates an iterator which uses a closure to determine if an element should be removed. 2795753dece8SMiguel Ojeda /// 2796753dece8SMiguel Ojeda /// If the closure returns true, then the element is removed and yielded. 2797753dece8SMiguel Ojeda /// If the closure returns false, the element will remain in the vector and will not be yielded 2798753dece8SMiguel Ojeda /// by the iterator. 2799753dece8SMiguel Ojeda /// 2800753dece8SMiguel Ojeda /// Using this method is equivalent to the following code: 2801753dece8SMiguel Ojeda /// 2802753dece8SMiguel Ojeda /// ``` 2803753dece8SMiguel Ojeda /// # let some_predicate = |x: &mut i32| { *x == 2 || *x == 3 || *x == 6 }; 2804753dece8SMiguel Ojeda /// # let mut vec = vec![1, 2, 3, 4, 5, 6]; 2805753dece8SMiguel Ojeda /// let mut i = 0; 2806753dece8SMiguel Ojeda /// while i < vec.len() { 2807753dece8SMiguel Ojeda /// if some_predicate(&mut vec[i]) { 2808753dece8SMiguel Ojeda /// let val = vec.remove(i); 2809753dece8SMiguel Ojeda /// // your code here 2810753dece8SMiguel Ojeda /// } else { 2811753dece8SMiguel Ojeda /// i += 1; 2812753dece8SMiguel Ojeda /// } 2813753dece8SMiguel Ojeda /// } 2814753dece8SMiguel Ojeda /// 2815753dece8SMiguel Ojeda /// # assert_eq!(vec, vec![1, 4, 5]); 2816753dece8SMiguel Ojeda /// ``` 2817753dece8SMiguel Ojeda /// 2818753dece8SMiguel Ojeda /// But `drain_filter` is easier to use. `drain_filter` is also more efficient, 2819753dece8SMiguel Ojeda /// because it can backshift the elements of the array in bulk. 2820753dece8SMiguel Ojeda /// 2821753dece8SMiguel Ojeda /// Note that `drain_filter` also lets you mutate every element in the filter closure, 2822753dece8SMiguel Ojeda /// regardless of whether you choose to keep or remove it. 2823753dece8SMiguel Ojeda /// 2824753dece8SMiguel Ojeda /// # Examples 2825753dece8SMiguel Ojeda /// 2826753dece8SMiguel Ojeda /// Splitting an array into evens and odds, reusing the original allocation: 2827753dece8SMiguel Ojeda /// 2828753dece8SMiguel Ojeda /// ``` 2829753dece8SMiguel Ojeda /// #![feature(drain_filter)] 2830753dece8SMiguel Ojeda /// let mut numbers = vec![1, 2, 3, 4, 5, 6, 8, 9, 11, 13, 14, 15]; 2831753dece8SMiguel Ojeda /// 2832753dece8SMiguel Ojeda /// let evens = numbers.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>(); 2833753dece8SMiguel Ojeda /// let odds = numbers; 2834753dece8SMiguel Ojeda /// 2835753dece8SMiguel Ojeda /// assert_eq!(evens, vec![2, 4, 6, 8, 14]); 2836753dece8SMiguel Ojeda /// assert_eq!(odds, vec![1, 3, 5, 9, 11, 13, 15]); 2837753dece8SMiguel Ojeda /// ``` 2838753dece8SMiguel Ojeda #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")] 2839753dece8SMiguel Ojeda pub fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<'_, T, F, A> 2840753dece8SMiguel Ojeda where 2841753dece8SMiguel Ojeda F: FnMut(&mut T) -> bool, 2842753dece8SMiguel Ojeda { 2843753dece8SMiguel Ojeda let old_len = self.len(); 2844753dece8SMiguel Ojeda 2845753dece8SMiguel Ojeda // Guard against us getting leaked (leak amplification) 2846753dece8SMiguel Ojeda unsafe { 2847753dece8SMiguel Ojeda self.set_len(0); 2848753dece8SMiguel Ojeda } 2849753dece8SMiguel Ojeda 2850753dece8SMiguel Ojeda DrainFilter { vec: self, idx: 0, del: 0, old_len, pred: filter, panic_flag: false } 2851753dece8SMiguel Ojeda } 2852753dece8SMiguel Ojeda } 2853753dece8SMiguel Ojeda 2854753dece8SMiguel Ojeda /// Extend implementation that copies elements out of references before pushing them onto the Vec. 2855753dece8SMiguel Ojeda /// 2856753dece8SMiguel Ojeda /// This implementation is specialized for slice iterators, where it uses [`copy_from_slice`] to 2857753dece8SMiguel Ojeda /// append the entire slice at once. 2858753dece8SMiguel Ojeda /// 2859753dece8SMiguel Ojeda /// [`copy_from_slice`]: slice::copy_from_slice 2860753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2861753dece8SMiguel Ojeda #[stable(feature = "extend_ref", since = "1.2.0")] 2862753dece8SMiguel Ojeda impl<'a, T: Copy + 'a, A: Allocator + 'a> Extend<&'a T> for Vec<T, A> { 2863753dece8SMiguel Ojeda fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) { 2864753dece8SMiguel Ojeda self.spec_extend(iter.into_iter()) 2865753dece8SMiguel Ojeda } 2866753dece8SMiguel Ojeda 2867753dece8SMiguel Ojeda #[inline] 2868753dece8SMiguel Ojeda fn extend_one(&mut self, &item: &'a T) { 2869753dece8SMiguel Ojeda self.push(item); 2870753dece8SMiguel Ojeda } 2871753dece8SMiguel Ojeda 2872753dece8SMiguel Ojeda #[inline] 2873753dece8SMiguel Ojeda fn extend_reserve(&mut self, additional: usize) { 2874753dece8SMiguel Ojeda self.reserve(additional); 2875753dece8SMiguel Ojeda } 2876753dece8SMiguel Ojeda } 2877753dece8SMiguel Ojeda 2878753dece8SMiguel Ojeda /// Implements comparison of vectors, [lexicographically](core::cmp::Ord#lexicographical-comparison). 2879753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2880753dece8SMiguel Ojeda impl<T: PartialOrd, A: Allocator> PartialOrd for Vec<T, A> { 2881753dece8SMiguel Ojeda #[inline] 2882753dece8SMiguel Ojeda fn partial_cmp(&self, other: &Self) -> Option<Ordering> { 2883753dece8SMiguel Ojeda PartialOrd::partial_cmp(&**self, &**other) 2884753dece8SMiguel Ojeda } 2885753dece8SMiguel Ojeda } 2886753dece8SMiguel Ojeda 2887753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2888753dece8SMiguel Ojeda impl<T: Eq, A: Allocator> Eq for Vec<T, A> {} 2889753dece8SMiguel Ojeda 2890753dece8SMiguel Ojeda /// Implements ordering of vectors, [lexicographically](core::cmp::Ord#lexicographical-comparison). 2891753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2892753dece8SMiguel Ojeda impl<T: Ord, A: Allocator> Ord for Vec<T, A> { 2893753dece8SMiguel Ojeda #[inline] 2894753dece8SMiguel Ojeda fn cmp(&self, other: &Self) -> Ordering { 2895753dece8SMiguel Ojeda Ord::cmp(&**self, &**other) 2896753dece8SMiguel Ojeda } 2897753dece8SMiguel Ojeda } 2898753dece8SMiguel Ojeda 2899753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2900753dece8SMiguel Ojeda unsafe impl<#[may_dangle] T, A: Allocator> Drop for Vec<T, A> { 2901753dece8SMiguel Ojeda fn drop(&mut self) { 2902753dece8SMiguel Ojeda unsafe { 2903753dece8SMiguel Ojeda // use drop for [T] 2904753dece8SMiguel Ojeda // use a raw slice to refer to the elements of the vector as weakest necessary type; 2905753dece8SMiguel Ojeda // could avoid questions of validity in certain cases 2906753dece8SMiguel Ojeda ptr::drop_in_place(ptr::slice_from_raw_parts_mut(self.as_mut_ptr(), self.len)) 2907753dece8SMiguel Ojeda } 2908753dece8SMiguel Ojeda // RawVec handles deallocation 2909753dece8SMiguel Ojeda } 2910753dece8SMiguel Ojeda } 2911753dece8SMiguel Ojeda 2912753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2913753dece8SMiguel Ojeda #[rustc_const_unstable(feature = "const_default_impls", issue = "87864")] 2914753dece8SMiguel Ojeda impl<T> const Default for Vec<T> { 2915753dece8SMiguel Ojeda /// Creates an empty `Vec<T>`. 2916753dece8SMiguel Ojeda fn default() -> Vec<T> { 2917753dece8SMiguel Ojeda Vec::new() 2918753dece8SMiguel Ojeda } 2919753dece8SMiguel Ojeda } 2920753dece8SMiguel Ojeda 2921753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2922753dece8SMiguel Ojeda impl<T: fmt::Debug, A: Allocator> fmt::Debug for Vec<T, A> { 2923753dece8SMiguel Ojeda fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { 2924753dece8SMiguel Ojeda fmt::Debug::fmt(&**self, f) 2925753dece8SMiguel Ojeda } 2926753dece8SMiguel Ojeda } 2927753dece8SMiguel Ojeda 2928753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2929753dece8SMiguel Ojeda impl<T, A: Allocator> AsRef<Vec<T, A>> for Vec<T, A> { 2930753dece8SMiguel Ojeda fn as_ref(&self) -> &Vec<T, A> { 2931753dece8SMiguel Ojeda self 2932753dece8SMiguel Ojeda } 2933753dece8SMiguel Ojeda } 2934753dece8SMiguel Ojeda 2935753dece8SMiguel Ojeda #[stable(feature = "vec_as_mut", since = "1.5.0")] 2936753dece8SMiguel Ojeda impl<T, A: Allocator> AsMut<Vec<T, A>> for Vec<T, A> { 2937753dece8SMiguel Ojeda fn as_mut(&mut self) -> &mut Vec<T, A> { 2938753dece8SMiguel Ojeda self 2939753dece8SMiguel Ojeda } 2940753dece8SMiguel Ojeda } 2941753dece8SMiguel Ojeda 2942753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2943753dece8SMiguel Ojeda impl<T, A: Allocator> AsRef<[T]> for Vec<T, A> { 2944753dece8SMiguel Ojeda fn as_ref(&self) -> &[T] { 2945753dece8SMiguel Ojeda self 2946753dece8SMiguel Ojeda } 2947753dece8SMiguel Ojeda } 2948753dece8SMiguel Ojeda 2949753dece8SMiguel Ojeda #[stable(feature = "vec_as_mut", since = "1.5.0")] 2950753dece8SMiguel Ojeda impl<T, A: Allocator> AsMut<[T]> for Vec<T, A> { 2951753dece8SMiguel Ojeda fn as_mut(&mut self) -> &mut [T] { 2952753dece8SMiguel Ojeda self 2953753dece8SMiguel Ojeda } 2954753dece8SMiguel Ojeda } 2955753dece8SMiguel Ojeda 2956753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2957753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 2958753dece8SMiguel Ojeda impl<T: Clone> From<&[T]> for Vec<T> { 2959753dece8SMiguel Ojeda /// Allocate a `Vec<T>` and fill it by cloning `s`'s items. 2960753dece8SMiguel Ojeda /// 2961753dece8SMiguel Ojeda /// # Examples 2962753dece8SMiguel Ojeda /// 2963753dece8SMiguel Ojeda /// ``` 2964753dece8SMiguel Ojeda /// assert_eq!(Vec::from(&[1, 2, 3][..]), vec![1, 2, 3]); 2965753dece8SMiguel Ojeda /// ``` 2966753dece8SMiguel Ojeda #[cfg(not(test))] 2967753dece8SMiguel Ojeda fn from(s: &[T]) -> Vec<T> { 2968753dece8SMiguel Ojeda s.to_vec() 2969753dece8SMiguel Ojeda } 2970753dece8SMiguel Ojeda #[cfg(test)] 2971753dece8SMiguel Ojeda fn from(s: &[T]) -> Vec<T> { 2972753dece8SMiguel Ojeda crate::slice::to_vec(s, Global) 2973753dece8SMiguel Ojeda } 2974753dece8SMiguel Ojeda } 2975753dece8SMiguel Ojeda 2976753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2977753dece8SMiguel Ojeda #[stable(feature = "vec_from_mut", since = "1.19.0")] 2978753dece8SMiguel Ojeda impl<T: Clone> From<&mut [T]> for Vec<T> { 2979753dece8SMiguel Ojeda /// Allocate a `Vec<T>` and fill it by cloning `s`'s items. 2980753dece8SMiguel Ojeda /// 2981753dece8SMiguel Ojeda /// # Examples 2982753dece8SMiguel Ojeda /// 2983753dece8SMiguel Ojeda /// ``` 2984753dece8SMiguel Ojeda /// assert_eq!(Vec::from(&mut [1, 2, 3][..]), vec![1, 2, 3]); 2985753dece8SMiguel Ojeda /// ``` 2986753dece8SMiguel Ojeda #[cfg(not(test))] 2987753dece8SMiguel Ojeda fn from(s: &mut [T]) -> Vec<T> { 2988753dece8SMiguel Ojeda s.to_vec() 2989753dece8SMiguel Ojeda } 2990753dece8SMiguel Ojeda #[cfg(test)] 2991753dece8SMiguel Ojeda fn from(s: &mut [T]) -> Vec<T> { 2992753dece8SMiguel Ojeda crate::slice::to_vec(s, Global) 2993753dece8SMiguel Ojeda } 2994753dece8SMiguel Ojeda } 2995753dece8SMiguel Ojeda 2996753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 2997753dece8SMiguel Ojeda #[stable(feature = "vec_from_array", since = "1.44.0")] 2998753dece8SMiguel Ojeda impl<T, const N: usize> From<[T; N]> for Vec<T> { 2999753dece8SMiguel Ojeda /// Allocate a `Vec<T>` and move `s`'s items into it. 3000753dece8SMiguel Ojeda /// 3001753dece8SMiguel Ojeda /// # Examples 3002753dece8SMiguel Ojeda /// 3003753dece8SMiguel Ojeda /// ``` 3004753dece8SMiguel Ojeda /// assert_eq!(Vec::from([1, 2, 3]), vec![1, 2, 3]); 3005753dece8SMiguel Ojeda /// ``` 3006753dece8SMiguel Ojeda #[cfg(not(test))] 3007753dece8SMiguel Ojeda fn from(s: [T; N]) -> Vec<T> { 3008753dece8SMiguel Ojeda <[T]>::into_vec(box s) 3009753dece8SMiguel Ojeda } 3010753dece8SMiguel Ojeda 3011753dece8SMiguel Ojeda #[cfg(test)] 3012753dece8SMiguel Ojeda fn from(s: [T; N]) -> Vec<T> { 3013753dece8SMiguel Ojeda crate::slice::into_vec(box s) 3014753dece8SMiguel Ojeda } 3015753dece8SMiguel Ojeda } 3016753dece8SMiguel Ojeda 3017753dece8SMiguel Ojeda #[stable(feature = "vec_from_cow_slice", since = "1.14.0")] 3018753dece8SMiguel Ojeda impl<'a, T> From<Cow<'a, [T]>> for Vec<T> 3019753dece8SMiguel Ojeda where 3020753dece8SMiguel Ojeda [T]: ToOwned<Owned = Vec<T>>, 3021753dece8SMiguel Ojeda { 3022753dece8SMiguel Ojeda /// Convert a clone-on-write slice into a vector. 3023753dece8SMiguel Ojeda /// 3024753dece8SMiguel Ojeda /// If `s` already owns a `Vec<T>`, it will be returned directly. 3025753dece8SMiguel Ojeda /// If `s` is borrowing a slice, a new `Vec<T>` will be allocated and 3026753dece8SMiguel Ojeda /// filled by cloning `s`'s items into it. 3027753dece8SMiguel Ojeda /// 3028753dece8SMiguel Ojeda /// # Examples 3029753dece8SMiguel Ojeda /// 3030753dece8SMiguel Ojeda /// ``` 3031753dece8SMiguel Ojeda /// # use std::borrow::Cow; 3032753dece8SMiguel Ojeda /// let o: Cow<[i32]> = Cow::Owned(vec![1, 2, 3]); 3033753dece8SMiguel Ojeda /// let b: Cow<[i32]> = Cow::Borrowed(&[1, 2, 3]); 3034753dece8SMiguel Ojeda /// assert_eq!(Vec::from(o), Vec::from(b)); 3035753dece8SMiguel Ojeda /// ``` 3036753dece8SMiguel Ojeda fn from(s: Cow<'a, [T]>) -> Vec<T> { 3037753dece8SMiguel Ojeda s.into_owned() 3038753dece8SMiguel Ojeda } 3039753dece8SMiguel Ojeda } 3040753dece8SMiguel Ojeda 3041753dece8SMiguel Ojeda // note: test pulls in libstd, which causes errors here 3042753dece8SMiguel Ojeda #[cfg(not(test))] 3043753dece8SMiguel Ojeda #[stable(feature = "vec_from_box", since = "1.18.0")] 3044753dece8SMiguel Ojeda impl<T, A: Allocator> From<Box<[T], A>> for Vec<T, A> { 3045753dece8SMiguel Ojeda /// Convert a boxed slice into a vector by transferring ownership of 3046753dece8SMiguel Ojeda /// the existing heap allocation. 3047753dece8SMiguel Ojeda /// 3048753dece8SMiguel Ojeda /// # Examples 3049753dece8SMiguel Ojeda /// 3050753dece8SMiguel Ojeda /// ``` 3051753dece8SMiguel Ojeda /// let b: Box<[i32]> = vec![1, 2, 3].into_boxed_slice(); 3052753dece8SMiguel Ojeda /// assert_eq!(Vec::from(b), vec![1, 2, 3]); 3053753dece8SMiguel Ojeda /// ``` 3054753dece8SMiguel Ojeda fn from(s: Box<[T], A>) -> Self { 3055753dece8SMiguel Ojeda s.into_vec() 3056753dece8SMiguel Ojeda } 3057753dece8SMiguel Ojeda } 3058753dece8SMiguel Ojeda 3059753dece8SMiguel Ojeda // note: test pulls in libstd, which causes errors here 3060753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 3061753dece8SMiguel Ojeda #[cfg(not(test))] 3062753dece8SMiguel Ojeda #[stable(feature = "box_from_vec", since = "1.20.0")] 3063753dece8SMiguel Ojeda impl<T, A: Allocator> From<Vec<T, A>> for Box<[T], A> { 3064753dece8SMiguel Ojeda /// Convert a vector into a boxed slice. 3065753dece8SMiguel Ojeda /// 3066753dece8SMiguel Ojeda /// If `v` has excess capacity, its items will be moved into a 3067753dece8SMiguel Ojeda /// newly-allocated buffer with exactly the right capacity. 3068753dece8SMiguel Ojeda /// 3069753dece8SMiguel Ojeda /// # Examples 3070753dece8SMiguel Ojeda /// 3071753dece8SMiguel Ojeda /// ``` 3072753dece8SMiguel Ojeda /// assert_eq!(Box::from(vec![1, 2, 3]), vec![1, 2, 3].into_boxed_slice()); 3073753dece8SMiguel Ojeda /// ``` 3074753dece8SMiguel Ojeda fn from(v: Vec<T, A>) -> Self { 3075753dece8SMiguel Ojeda v.into_boxed_slice() 3076753dece8SMiguel Ojeda } 3077753dece8SMiguel Ojeda } 3078753dece8SMiguel Ojeda 3079753dece8SMiguel Ojeda #[cfg(not(no_global_oom_handling))] 3080753dece8SMiguel Ojeda #[stable(feature = "rust1", since = "1.0.0")] 3081753dece8SMiguel Ojeda impl From<&str> for Vec<u8> { 3082753dece8SMiguel Ojeda /// Allocate a `Vec<u8>` and fill it with a UTF-8 string. 3083753dece8SMiguel Ojeda /// 3084753dece8SMiguel Ojeda /// # Examples 3085753dece8SMiguel Ojeda /// 3086753dece8SMiguel Ojeda /// ``` 3087753dece8SMiguel Ojeda /// assert_eq!(Vec::from("123"), vec![b'1', b'2', b'3']); 3088753dece8SMiguel Ojeda /// ``` 3089753dece8SMiguel Ojeda fn from(s: &str) -> Vec<u8> { 3090753dece8SMiguel Ojeda From::from(s.as_bytes()) 3091753dece8SMiguel Ojeda } 3092753dece8SMiguel Ojeda } 3093753dece8SMiguel Ojeda 3094753dece8SMiguel Ojeda #[stable(feature = "array_try_from_vec", since = "1.48.0")] 3095753dece8SMiguel Ojeda impl<T, A: Allocator, const N: usize> TryFrom<Vec<T, A>> for [T; N] { 3096753dece8SMiguel Ojeda type Error = Vec<T, A>; 3097753dece8SMiguel Ojeda 3098753dece8SMiguel Ojeda /// Gets the entire contents of the `Vec<T>` as an array, 3099753dece8SMiguel Ojeda /// if its size exactly matches that of the requested array. 3100753dece8SMiguel Ojeda /// 3101753dece8SMiguel Ojeda /// # Examples 3102753dece8SMiguel Ojeda /// 3103753dece8SMiguel Ojeda /// ``` 3104753dece8SMiguel Ojeda /// assert_eq!(vec![1, 2, 3].try_into(), Ok([1, 2, 3])); 3105753dece8SMiguel Ojeda /// assert_eq!(<Vec<i32>>::new().try_into(), Ok([])); 3106753dece8SMiguel Ojeda /// ``` 3107753dece8SMiguel Ojeda /// 3108753dece8SMiguel Ojeda /// If the length doesn't match, the input comes back in `Err`: 3109753dece8SMiguel Ojeda /// ``` 3110753dece8SMiguel Ojeda /// let r: Result<[i32; 4], _> = (0..10).collect::<Vec<_>>().try_into(); 3111753dece8SMiguel Ojeda /// assert_eq!(r, Err(vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9])); 3112753dece8SMiguel Ojeda /// ``` 3113753dece8SMiguel Ojeda /// 3114753dece8SMiguel Ojeda /// If you're fine with just getting a prefix of the `Vec<T>`, 3115753dece8SMiguel Ojeda /// you can call [`.truncate(N)`](Vec::truncate) first. 3116753dece8SMiguel Ojeda /// ``` 3117753dece8SMiguel Ojeda /// let mut v = String::from("hello world").into_bytes(); 3118753dece8SMiguel Ojeda /// v.sort(); 3119753dece8SMiguel Ojeda /// v.truncate(2); 3120753dece8SMiguel Ojeda /// let [a, b]: [_; 2] = v.try_into().unwrap(); 3121753dece8SMiguel Ojeda /// assert_eq!(a, b' '); 3122753dece8SMiguel Ojeda /// assert_eq!(b, b'd'); 3123753dece8SMiguel Ojeda /// ``` 3124753dece8SMiguel Ojeda fn try_from(mut vec: Vec<T, A>) -> Result<[T; N], Vec<T, A>> { 3125753dece8SMiguel Ojeda if vec.len() != N { 3126753dece8SMiguel Ojeda return Err(vec); 3127753dece8SMiguel Ojeda } 3128753dece8SMiguel Ojeda 3129753dece8SMiguel Ojeda // SAFETY: `.set_len(0)` is always sound. 3130753dece8SMiguel Ojeda unsafe { vec.set_len(0) }; 3131753dece8SMiguel Ojeda 3132753dece8SMiguel Ojeda // SAFETY: A `Vec`'s pointer is always aligned properly, and 3133753dece8SMiguel Ojeda // the alignment the array needs is the same as the items. 3134753dece8SMiguel Ojeda // We checked earlier that we have sufficient items. 3135753dece8SMiguel Ojeda // The items will not double-drop as the `set_len` 3136753dece8SMiguel Ojeda // tells the `Vec` not to also drop them. 3137753dece8SMiguel Ojeda let array = unsafe { ptr::read(vec.as_ptr() as *const [T; N]) }; 3138753dece8SMiguel Ojeda Ok(array) 3139753dece8SMiguel Ojeda } 3140753dece8SMiguel Ojeda } 3141