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 = idx * BITS_PER_LONG + fns(tmp, nr);                                \
  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 /*
 120  * Find the first set bit in three memory regions.
 121  */
 122 unsigned long _find_first_and_and_bit(const unsigned long *addr1,
 123                                       const unsigned long *addr2,
 124                                       const unsigned long *addr3,
 125                                       unsigned long size)
 126 {
 127         return FIND_FIRST_BIT(addr1[idx] & addr2[idx] & addr3[idx], /* nop */, size);
 128 }
 129 EXPORT_SYMBOL(_find_first_and_and_bit);
 130
 131 #ifndef find_first_zero_bit
 132 /*
 133  * Find the first cleared bit in a memory region.
 134  */
 135 unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)
 136 {
 137         return FIND_FIRST_BIT(~addr[idx], /* nop */, size);
 138 }
 139 EXPORT_SYMBOL(_find_first_zero_bit);
 140 #endif
 141
 142 #ifndef find_next_bit
 143 unsigned long _find_next_bit(const unsigned long *addr, unsigned long nbits, unsigned long start)
 144 {
 145         return FIND_NEXT_BIT(addr[idx], /* nop */, nbits, start);
 146 }
 147 EXPORT_SYMBOL(_find_next_bit);
 148 #endif
 149
 150 unsigned long __find_nth_bit(const unsigned long *addr, unsigned long size, unsigned long n)
 151 {
 152         return FIND_NTH_BIT(addr[idx], size, n);
 153 }
 154 EXPORT_SYMBOL(__find_nth_bit);
 155
 156 unsigned long __find_nth_and_bit(const unsigned long *addr1, const unsigned long *addr2,
 157                                  unsigned long size, unsigned long n)
 158 {
 159         return FIND_NTH_BIT(addr1[idx] & addr2[idx], size, n);
 160 }
 161 EXPORT_SYMBOL(__find_nth_and_bit);
 162
 163 unsigned long __find_nth_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
 164                                  unsigned long size, unsigned long n)
 165 {
 166         return FIND_NTH_BIT(addr1[idx] & ~addr2[idx], size, n);
 167 }
 168 EXPORT_SYMBOL(__find_nth_andnot_bit);
 169
 170 unsigned long __find_nth_and_andnot_bit(const unsigned long *addr1,
 171                                         const unsigned long *addr2,
 172                                         const unsigned long *addr3,
 173                                         unsigned long size, unsigned long n)
 174 {
 175         return FIND_NTH_BIT(addr1[idx] & addr2[idx] & ~addr3[idx], size, n);
 176 }
 177 EXPORT_SYMBOL(__find_nth_and_andnot_bit);
 178
 179 #ifndef find_next_and_bit
 180 unsigned long _find_next_and_bit(const unsigned long *addr1, const unsigned long *addr2,
 181                                         unsigned long nbits, unsigned long start)
 182 {
 183         return FIND_NEXT_BIT(addr1[idx] & addr2[idx], /* nop */, nbits, start);
 184 }
 185 EXPORT_SYMBOL(_find_next_and_bit);
 186 #endif
 187
 188 #ifndef find_next_andnot_bit
 189 unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
 190                                         unsigned long nbits, unsigned long start)
 191 {
 192         return FIND_NEXT_BIT(addr1[idx] & ~addr2[idx], /* nop */, nbits, start);
 193 }
 194 EXPORT_SYMBOL(_find_next_andnot_bit);
 195 #endif
 196
 197 #ifndef find_next_or_bit
 198 unsigned long _find_next_or_bit(const unsigned long *addr1, const unsigned long *addr2,
 199                                         unsigned long nbits, unsigned long start)
 200 {
 201         return FIND_NEXT_BIT(addr1[idx] | addr2[idx], /* nop */, nbits, start);
 202 }
 203 EXPORT_SYMBOL(_find_next_or_bit);
 204 #endif
 205
 206 #ifndef find_next_zero_bit
 207 unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits,
 208                                          unsigned long start)
 209 {
 210         return FIND_NEXT_BIT(~addr[idx], /* nop */, nbits, start);
 211 }
 212 EXPORT_SYMBOL(_find_next_zero_bit);
 213 #endif
 214
 215 #ifndef find_last_bit
 216 unsigned long _find_last_bit(const unsigned long *addr, unsigned long size)
 217 {
 218         if (size) {
 219                 unsigned long val = BITMAP_LAST_WORD_MASK(size);
 220                 unsigned long idx = (size-1) / BITS_PER_LONG;
 221
 222                 do {
 223                         val &= addr[idx];
 224                         if (val)
 225                                 return idx * BITS_PER_LONG + __fls(val);
 226
 227                         val = ~0ul;
 228                 } while (idx--);
 229         }
 230         return size;
 231 }
 232 EXPORT_SYMBOL(_find_last_bit);
 233 #endif
 234
 235 unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr,
 236                                unsigned long size, unsigned long offset)
 237 {
 238         offset = find_next_bit(addr, size, offset);
 239         if (offset == size)
 240                 return size;
 241
 242         offset = round_down(offset, 8);
 243         *clump = bitmap_get_value8(addr, offset);
 244
 245         return offset;
 246 }
 247 EXPORT_SYMBOL(find_next_clump8);
 248
 249 #ifdef __BIG_ENDIAN
 250
 251 #ifndef find_first_zero_bit_le
 252 /*
 253  * Find the first cleared bit in an LE memory region.
 254  */
 255 unsigned long _find_first_zero_bit_le(const unsigned long *addr, unsigned long size)
 256 {
 257         return FIND_FIRST_BIT(~addr[idx], swab, size);
 258 }
 259 EXPORT_SYMBOL(_find_first_zero_bit_le);
 260
 261 #endif
 262
 263 #ifndef find_next_zero_bit_le
 264 unsigned long _find_next_zero_bit_le(const unsigned long *addr,
 265                                         unsigned long size, unsigned long offset)
 266 {
 267         return FIND_NEXT_BIT(~addr[idx], swab, size, offset);
 268 }
 269 EXPORT_SYMBOL(_find_next_zero_bit_le);
 270 #endif
 271
 272 #ifndef find_next_bit_le
 273 unsigned long _find_next_bit_le(const unsigned long *addr,
 274                                 unsigned long size, unsigned long offset)
 275 {
 276         return FIND_NEXT_BIT(addr[idx], swab, size, offset);
 277 }
 278 EXPORT_SYMBOL(_find_next_bit_le);
 279
 280 #endif
 281
 282 #endif /* __BIG_ENDIAN */