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/math.h>
  19 #include <linux/minmax.h>
  20 #include <linux/swab.h>
  21
  22 /*
  23  * Common helper for find_bit() function family
  24  * @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
  25  * @MUNGE: The expression that post-processes a word containing found bit (may be empty)
  26  * @size: The bitmap size in bits
  27  */
  28 #define FIND_FIRST_BIT(FETCH, MUNGE, size)                                      \
  29 ({                                                                              \
  30         unsigned long idx, val, sz = (size);                                    \
  31                                                                                 \
  32         for (idx = 0; idx * BITS_PER_LONG < sz; idx++) {                        \
  33                 val = (FETCH);                                                  \
  34                 if (val) {                                                      \
  35                         sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(val)), sz);  \
  36                         break;                                                  \
  37                 }                                                               \
  38         }                                                                       \
  39                                                                                 \
  40         sz;                                                                     \
  41 })
  42
  43 /*
  44  * Common helper for find_next_bit() function family
  45  * @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
  46  * @MUNGE: The expression that post-processes a word containing found bit (may be empty)
  47  * @size: The bitmap size in bits
  48  * @start: The bitnumber to start searching at
  49  */
  50 #define FIND_NEXT_BIT(FETCH, MUNGE, size, start)                                \
  51 ({                                                                              \
  52         unsigned long mask, idx, tmp, sz = (size), __start = (start);           \
  53                                                                                 \
  54         if (unlikely(__start >= sz))                                            \
  55                 goto out;                                                       \
  56                                                                                 \
  57         mask = MUNGE(BITMAP_FIRST_WORD_MASK(__start));                          \
  58         idx = __start / BITS_PER_LONG;                                          \
  59                                                                                 \
  60         for (tmp = (FETCH) & mask; !tmp; tmp = (FETCH)) {                       \
  61                 if ((idx + 1) * BITS_PER_LONG >= sz)                            \
  62                         goto out;                                               \
  63                 idx++;                                                          \
  64         }                                                                       \
  65                                                                                 \
  66         sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(tmp)), sz);                  \
  67 out:                                                                            \
  68         sz;                                                                     \
  69 })
  70
  71 #define FIND_NTH_BIT(FETCH, size, num)                                          \
  72 ({                                                                              \
  73         unsigned long sz = (size), nr = (num), idx, w, tmp;                     \
  74                                                                                 \
  75         for (idx = 0; (idx + 1) * BITS_PER_LONG <= sz; idx++) {                 \
  76                 if (idx * BITS_PER_LONG + nr >= sz)                             \
  77                         goto out;                                               \
  78                                                                                 \
  79                 tmp = (FETCH);                                                  \
  80                 w = hweight_long(tmp);                                          \
  81                 if (w > nr)                                                     \
  82                         goto found;                                             \
  83                                                                                 \
  84                 nr -= w;                                                        \
  85         }                                                                       \
  86                                                                                 \
  87         if (sz % BITS_PER_LONG)                                                 \
  88                 tmp = (FETCH) & BITMAP_LAST_WORD_MASK(sz);                      \
  89 found:                                                                          \
  90         sz = min(idx * BITS_PER_LONG + fns(tmp, nr), sz);                       \
  91 out:                                                                            \
  92         sz;                                                                     \
  93 })
  94
  95 #ifndef find_first_bit
  96 /*
  97  * Find the first set bit in a memory region.
  98  */
  99 unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)
 100 {
 101         return FIND_FIRST_BIT(addr[idx], /* nop */, size);
 102 }
 103 EXPORT_SYMBOL(_find_first_bit);
 104 #endif
 105
 106 #ifndef find_first_and_bit
 107 /*
 108  * Find the first set bit in two memory regions.
 109  */
 110 unsigned long _find_first_and_bit(const unsigned long *addr1,
 111                                   const unsigned long *addr2,
 112                                   unsigned long size)
 113 {
 114         return FIND_FIRST_BIT(addr1[idx] & addr2[idx], /* nop */, size);
 115 }
 116 EXPORT_SYMBOL(_find_first_and_bit);
 117 #endif
 118
 119 #ifndef find_first_zero_bit
 120 /*
 121  * Find the first cleared bit in a memory region.
 122  */
 123 unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)
 124 {
 125         return FIND_FIRST_BIT(~addr[idx], /* nop */, size);
 126 }
 127 EXPORT_SYMBOL(_find_first_zero_bit);
 128 #endif
 129
 130 #ifndef find_next_bit
 131 unsigned long _find_next_bit(const unsigned long *addr, unsigned long nbits, unsigned long start)
 132 {
 133         return FIND_NEXT_BIT(addr[idx], /* nop */, nbits, start);
 134 }
 135 EXPORT_SYMBOL(_find_next_bit);
 136 #endif
 137
 138 unsigned long __find_nth_bit(const unsigned long *addr, unsigned long size, unsigned long n)
 139 {
 140         return FIND_NTH_BIT(addr[idx], size, n);
 141 }
 142 EXPORT_SYMBOL(__find_nth_bit);
 143
 144 unsigned long __find_nth_and_bit(const unsigned long *addr1, const unsigned long *addr2,
 145                                  unsigned long size, unsigned long n)
 146 {
 147         return FIND_NTH_BIT(addr1[idx] & addr2[idx], size, n);
 148 }
 149 EXPORT_SYMBOL(__find_nth_and_bit);
 150
 151 unsigned long __find_nth_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
 152                                  unsigned long size, unsigned long n)
 153 {
 154         return FIND_NTH_BIT(addr1[idx] & ~addr2[idx], size, n);
 155 }
 156 EXPORT_SYMBOL(__find_nth_andnot_bit);
 157
 158 #ifndef find_next_and_bit
 159 unsigned long _find_next_and_bit(const unsigned long *addr1, const unsigned long *addr2,
 160                                         unsigned long nbits, unsigned long start)
 161 {
 162         return FIND_NEXT_BIT(addr1[idx] & addr2[idx], /* nop */, nbits, start);
 163 }
 164 EXPORT_SYMBOL(_find_next_and_bit);
 165 #endif
 166
 167 #ifndef find_next_andnot_bit
 168 unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
 169                                         unsigned long nbits, unsigned long start)
 170 {
 171         return FIND_NEXT_BIT(addr1[idx] & ~addr2[idx], /* nop */, nbits, start);
 172 }
 173 EXPORT_SYMBOL(_find_next_andnot_bit);
 174 #endif
 175
 176 #ifndef find_next_zero_bit
 177 unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits,
 178                                          unsigned long start)
 179 {
 180         return FIND_NEXT_BIT(~addr[idx], /* nop */, nbits, start);
 181 }
 182 EXPORT_SYMBOL(_find_next_zero_bit);
 183 #endif
 184
 185 #ifndef find_last_bit
 186 unsigned long _find_last_bit(const unsigned long *addr, unsigned long size)
 187 {
 188         if (size) {
 189                 unsigned long val = BITMAP_LAST_WORD_MASK(size);
 190                 unsigned long idx = (size-1) / BITS_PER_LONG;
 191
 192                 do {
 193                         val &= addr[idx];
 194                         if (val)
 195                                 return idx * BITS_PER_LONG + __fls(val);
 196
 197                         val = ~0ul;
 198                 } while (idx--);
 199         }
 200         return size;
 201 }
 202 EXPORT_SYMBOL(_find_last_bit);
 203 #endif
 204
 205 unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr,
 206                                unsigned long size, unsigned long offset)
 207 {
 208         offset = find_next_bit(addr, size, offset);
 209         if (offset == size)
 210                 return size;
 211
 212         offset = round_down(offset, 8);
 213         *clump = bitmap_get_value8(addr, offset);
 214
 215         return offset;
 216 }
 217 EXPORT_SYMBOL(find_next_clump8);
 218
 219 #ifdef __BIG_ENDIAN
 220
 221 #ifndef find_first_zero_bit_le
 222 /*
 223  * Find the first cleared bit in an LE memory region.
 224  */
 225 unsigned long _find_first_zero_bit_le(const unsigned long *addr, unsigned long size)
 226 {
 227         return FIND_FIRST_BIT(~addr[idx], swab, size);
 228 }
 229 EXPORT_SYMBOL(_find_first_zero_bit_le);
 230
 231 #endif
 232
 233 #ifndef find_next_zero_bit_le
 234 unsigned long _find_next_zero_bit_le(const unsigned long *addr,
 235                                         unsigned long size, unsigned long offset)
 236 {
 237         return FIND_NEXT_BIT(~addr[idx], swab, size, offset);
 238 }
 239 EXPORT_SYMBOL(_find_next_zero_bit_le);
 240 #endif
 241
 242 #ifndef find_next_bit_le
 243 unsigned long _find_next_bit_le(const unsigned long *addr,
 244                                 unsigned long size, unsigned long offset)
 245 {
 246         return FIND_NEXT_BIT(addr[idx], swab, size, offset);
 247 }
 248 EXPORT_SYMBOL(_find_next_bit_le);
 249
 250 #endif
 251
 252 #endif /* __BIG_ENDIAN */