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 static 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 #endif 72 73 #ifndef find_next_bit 74 /* 75 * Find the next set bit in a memory region. 76 */ 77 unsigned long find_next_bit(const unsigned long *addr, unsigned long size, 78 unsigned long offset) 79 { 80 return _find_next_bit(addr, NULL, size, offset, 0UL, 0); 81 } 82 EXPORT_SYMBOL(find_next_bit); 83 #endif 84 85 #ifndef find_next_zero_bit 86 unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size, 87 unsigned long offset) 88 { 89 return _find_next_bit(addr, NULL, size, offset, ~0UL, 0); 90 } 91 EXPORT_SYMBOL(find_next_zero_bit); 92 #endif 93 94 #if !defined(find_next_and_bit) 95 unsigned long find_next_and_bit(const unsigned long *addr1, 96 const unsigned long *addr2, unsigned long size, 97 unsigned long offset) 98 { 99 return _find_next_bit(addr1, addr2, size, offset, 0UL, 0); 100 } 101 EXPORT_SYMBOL(find_next_and_bit); 102 #endif 103 104 #ifndef find_first_bit 105 /* 106 * Find the first set bit in a memory region. 107 */ 108 unsigned long find_first_bit(const unsigned long *addr, unsigned long size) 109 { 110 unsigned long idx; 111 112 for (idx = 0; idx * BITS_PER_LONG < size; idx++) { 113 if (addr[idx]) 114 return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size); 115 } 116 117 return size; 118 } 119 EXPORT_SYMBOL(find_first_bit); 120 #endif 121 122 #ifndef find_first_zero_bit 123 /* 124 * Find the first cleared bit in a memory region. 125 */ 126 unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size) 127 { 128 unsigned long idx; 129 130 for (idx = 0; idx * BITS_PER_LONG < size; idx++) { 131 if (addr[idx] != ~0UL) 132 return min(idx * BITS_PER_LONG + ffz(addr[idx]), size); 133 } 134 135 return size; 136 } 137 EXPORT_SYMBOL(find_first_zero_bit); 138 #endif 139 140 #ifndef find_last_bit 141 unsigned long find_last_bit(const unsigned long *addr, unsigned long size) 142 { 143 if (size) { 144 unsigned long val = BITMAP_LAST_WORD_MASK(size); 145 unsigned long idx = (size-1) / BITS_PER_LONG; 146 147 do { 148 val &= addr[idx]; 149 if (val) 150 return idx * BITS_PER_LONG + __fls(val); 151 152 val = ~0ul; 153 } while (idx--); 154 } 155 return size; 156 } 157 EXPORT_SYMBOL(find_last_bit); 158 #endif 159 160 #ifdef __BIG_ENDIAN 161 162 #ifndef find_next_zero_bit_le 163 unsigned long find_next_zero_bit_le(const void *addr, unsigned 164 long size, unsigned long offset) 165 { 166 return _find_next_bit(addr, NULL, size, offset, ~0UL, 1); 167 } 168 EXPORT_SYMBOL(find_next_zero_bit_le); 169 #endif 170 171 #ifndef find_next_bit_le 172 unsigned long find_next_bit_le(const void *addr, unsigned 173 long size, unsigned long offset) 174 { 175 return _find_next_bit(addr, NULL, size, offset, 0UL, 1); 176 } 177 EXPORT_SYMBOL(find_next_bit_le); 178 #endif 179 180 #endif /* __BIG_ENDIAN */ 181 182 unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr, 183 unsigned long size, unsigned long offset) 184 { 185 offset = find_next_bit(addr, size, offset); 186 if (offset == size) 187 return size; 188 189 offset = round_down(offset, 8); 190 *clump = bitmap_get_value8(addr, offset); 191 192 return offset; 193 } 194 EXPORT_SYMBOL(find_next_clump8); 195