lib/find_bit.c

   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/kernel.h>
  19
  20 #if !defined(find_next_bit) || !defined(find_next_zero_bit) || \
  21                 !defined(find_next_and_bit)
  22
  23 /*
  24  * This is a common helper function for find_next_bit, find_next_zero_bit, and
  25  * find_next_and_bit. The differences are:
  26  *  - The "invert" argument, which is XORed with each fetched word before
  27  *    searching it for one bits.
  28  *  - The optional "addr2", which is anded with "addr1" if present.
  29  */
  30 static inline unsigned long _find_next_bit(const unsigned long *addr1,
  31                 const unsigned long *addr2, unsigned long nbits,
  32                 unsigned long start, unsigned long invert)
  33 {
  34         unsigned long tmp;
  35
  36         if (unlikely(start >= nbits))
  37                 return nbits;
  38
  39         tmp = addr1[start / BITS_PER_LONG];
  40         if (addr2)
  41                 tmp &= addr2[start / BITS_PER_LONG];
  42         tmp ^= invert;
  43
  44         /* Handle 1st word. */
  45         tmp &= BITMAP_FIRST_WORD_MASK(start);
  46         start = round_down(start, BITS_PER_LONG);
  47
  48         while (!tmp) {
  49                 start += BITS_PER_LONG;
  50                 if (start >= nbits)
  51                         return nbits;
  52
  53                 tmp = addr1[start / BITS_PER_LONG];
  54                 if (addr2)
  55                         tmp &= addr2[start / BITS_PER_LONG];
  56                 tmp ^= invert;
  57         }
  58
  59         return min(start + __ffs(tmp), nbits);
  60 }
  61 #endif
  62
  63 #ifndef find_next_bit
  64 /*
  65  * Find the next set bit in a memory region.
  66  */
  67 unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
  68                             unsigned long offset)
  69 {
  70         return _find_next_bit(addr, NULL, size, offset, 0UL);
  71 }
  72 EXPORT_SYMBOL(find_next_bit);
  73 #endif
  74
  75 #ifndef find_next_zero_bit
  76 unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
  77                                  unsigned long offset)
  78 {
  79         return _find_next_bit(addr, NULL, size, offset, ~0UL);
  80 }
  81 EXPORT_SYMBOL(find_next_zero_bit);
  82 #endif
  83
  84 #if !defined(find_next_and_bit)
  85 unsigned long find_next_and_bit(const unsigned long *addr1,
  86                 const unsigned long *addr2, unsigned long size,
  87                 unsigned long offset)
  88 {
  89         return _find_next_bit(addr1, addr2, size, offset, 0UL);
  90 }
  91 EXPORT_SYMBOL(find_next_and_bit);
  92 #endif
  93
  94 #ifndef find_first_bit
  95 /*
  96  * Find the first set bit in a memory region.
  97  */
  98 unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
  99 {
 100         unsigned long idx;
 101
 102         for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
 103                 if (addr[idx])
 104                         return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
 105         }
 106
 107         return size;
 108 }
 109 EXPORT_SYMBOL(find_first_bit);
 110 #endif
 111
 112 #ifndef find_first_zero_bit
 113 /*
 114  * Find the first cleared bit in a memory region.
 115  */
 116 unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
 117 {
 118         unsigned long idx;
 119
 120         for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
 121                 if (addr[idx] != ~0UL)
 122                         return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
 123         }
 124
 125         return size;
 126 }
 127 EXPORT_SYMBOL(find_first_zero_bit);
 128 #endif
 129
 130 #ifndef find_last_bit
 131 unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
 132 {
 133         if (size) {
 134                 unsigned long val = BITMAP_LAST_WORD_MASK(size);
 135                 unsigned long idx = (size-1) / BITS_PER_LONG;
 136
 137                 do {
 138                         val &= addr[idx];
 139                         if (val)
 140                                 return idx * BITS_PER_LONG + __fls(val);
 141
 142                         val = ~0ul;
 143                 } while (idx--);
 144         }
 145         return size;
 146 }
 147 EXPORT_SYMBOL(find_last_bit);
 148 #endif
 149
 150 #ifdef __BIG_ENDIAN
 151
 152 /* include/linux/byteorder does not support "unsigned long" type */
 153 static inline unsigned long ext2_swab(const unsigned long y)
 154 {
 155 #if BITS_PER_LONG == 64
 156         return (unsigned long) __swab64((u64) y);
 157 #elif BITS_PER_LONG == 32
 158         return (unsigned long) __swab32((u32) y);
 159 #else
 160 #error BITS_PER_LONG not defined
 161 #endif
 162 }
 163
 164 #if !defined(find_next_bit_le) || !defined(find_next_zero_bit_le)
 165 static inline unsigned long _find_next_bit_le(const unsigned long *addr1,
 166                 const unsigned long *addr2, unsigned long nbits,
 167                 unsigned long start, unsigned long invert)
 168 {
 169         unsigned long tmp;
 170
 171         if (unlikely(start >= nbits))
 172                 return nbits;
 173
 174         tmp = addr1[start / BITS_PER_LONG];
 175         if (addr2)
 176                 tmp &= addr2[start / BITS_PER_LONG];
 177         tmp ^= invert;
 178
 179         /* Handle 1st word. */
 180         tmp &= ext2_swab(BITMAP_FIRST_WORD_MASK(start));
 181         start = round_down(start, BITS_PER_LONG);
 182
 183         while (!tmp) {
 184                 start += BITS_PER_LONG;
 185                 if (start >= nbits)
 186                         return nbits;
 187
 188                 tmp = addr1[start / BITS_PER_LONG];
 189                 if (addr2)
 190                         tmp &= addr2[start / BITS_PER_LONG];
 191                 tmp ^= invert;
 192         }
 193
 194         return min(start + __ffs(ext2_swab(tmp)), nbits);
 195 }
 196 #endif
 197
 198 #ifndef find_next_zero_bit_le
 199 unsigned long find_next_zero_bit_le(const void *addr, unsigned
 200                 long size, unsigned long offset)
 201 {
 202         return _find_next_bit_le(addr, NULL, size, offset, ~0UL);
 203 }
 204 EXPORT_SYMBOL(find_next_zero_bit_le);
 205 #endif
 206
 207 #ifndef find_next_bit_le
 208 unsigned long find_next_bit_le(const void *addr, unsigned
 209                 long size, unsigned long offset)
 210 {
 211         return _find_next_bit_le(addr, NULL, size, offset, 0UL);
 212 }
 213 EXPORT_SYMBOL(find_next_bit_le);
 214 #endif
 215
 216 #endif /* __BIG_ENDIAN */