1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* bit search implementation 3 * 4 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved. 5 * Written by David Howells (dhowells@redhat.com) 6 * 7 * Copyright (C) 2008 IBM Corporation 8 * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au> 9 * (Inspired by David Howell's find_next_bit implementation) 10 * 11 * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease 12 * size and improve performance, 2015. 13 */ 14 15 #include <linux/bitops.h> 16 #include <linux/bitmap.h> 17 #include <linux/export.h> 18 #include <linux/math.h> 19 #include <linux/minmax.h> 20 #include <linux/swab.h> 21 22 #if !defined(find_next_bit) || !defined(find_next_zero_bit) || \ 23 !defined(find_next_bit_le) || !defined(find_next_zero_bit_le) || \ 24 !defined(find_next_and_bit) 25 /* 26 * This is a common helper function for find_next_bit, find_next_zero_bit, and 27 * find_next_and_bit. The differences are: 28 * - The "invert" argument, which is XORed with each fetched word before 29 * searching it for one bits. 30 * - The optional "addr2", which is anded with "addr1" if present. 31 */ 32 unsigned long _find_next_bit(const unsigned long *addr1, 33 const unsigned long *addr2, unsigned long nbits, 34 unsigned long start, unsigned long invert, unsigned long le) 35 { 36 unsigned long tmp, mask; 37 38 if (unlikely(start >= nbits)) 39 return nbits; 40 41 tmp = addr1[start / BITS_PER_LONG]; 42 if (addr2) 43 tmp &= addr2[start / BITS_PER_LONG]; 44 tmp ^= invert; 45 46 /* Handle 1st word. */ 47 mask = BITMAP_FIRST_WORD_MASK(start); 48 if (le) 49 mask = swab(mask); 50 51 tmp &= mask; 52 53 start = round_down(start, BITS_PER_LONG); 54 55 while (!tmp) { 56 start += BITS_PER_LONG; 57 if (start >= nbits) 58 return nbits; 59 60 tmp = addr1[start / BITS_PER_LONG]; 61 if (addr2) 62 tmp &= addr2[start / BITS_PER_LONG]; 63 tmp ^= invert; 64 } 65 66 if (le) 67 tmp = swab(tmp); 68 69 return min(start + __ffs(tmp), nbits); 70 } 71 EXPORT_SYMBOL(_find_next_bit); 72 #endif 73 74 #ifndef find_first_bit 75 /* 76 * Find the first set bit in a memory region. 77 */ 78 unsigned long _find_first_bit(const unsigned long *addr, unsigned long size) 79 { 80 unsigned long idx; 81 82 for (idx = 0; idx * BITS_PER_LONG < size; idx++) { 83 if (addr[idx]) 84 return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size); 85 } 86 87 return size; 88 } 89 EXPORT_SYMBOL(_find_first_bit); 90 #endif 91 92 #ifndef find_first_and_bit 93 /* 94 * Find the first set bit in two memory regions. 95 */ 96 unsigned long _find_first_and_bit(const unsigned long *addr1, 97 const unsigned long *addr2, 98 unsigned long size) 99 { 100 unsigned long idx, val; 101 102 for (idx = 0; idx * BITS_PER_LONG < size; idx++) { 103 val = addr1[idx] & addr2[idx]; 104 if (val) 105 return min(idx * BITS_PER_LONG + __ffs(val), size); 106 } 107 108 return size; 109 } 110 EXPORT_SYMBOL(_find_first_and_bit); 111 #endif 112 113 #ifndef find_first_zero_bit 114 /* 115 * Find the first cleared bit in a memory region. 116 */ 117 unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size) 118 { 119 unsigned long idx; 120 121 for (idx = 0; idx * BITS_PER_LONG < size; idx++) { 122 if (addr[idx] != ~0UL) 123 return min(idx * BITS_PER_LONG + ffz(addr[idx]), size); 124 } 125 126 return size; 127 } 128 EXPORT_SYMBOL(_find_first_zero_bit); 129 #endif 130 131 #ifndef find_last_bit 132 unsigned long _find_last_bit(const unsigned long *addr, unsigned long size) 133 { 134 if (size) { 135 unsigned long val = BITMAP_LAST_WORD_MASK(size); 136 unsigned long idx = (size-1) / BITS_PER_LONG; 137 138 do { 139 val &= addr[idx]; 140 if (val) 141 return idx * BITS_PER_LONG + __fls(val); 142 143 val = ~0ul; 144 } while (idx--); 145 } 146 return size; 147 } 148 EXPORT_SYMBOL(_find_last_bit); 149 #endif 150 151 unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr, 152 unsigned long size, unsigned long offset) 153 { 154 offset = find_next_bit(addr, size, offset); 155 if (offset == size) 156 return size; 157 158 offset = round_down(offset, 8); 159 *clump = bitmap_get_value8(addr, offset); 160 161 return offset; 162 } 163 EXPORT_SYMBOL(find_next_clump8); 164