util/bitmap.c

   1 /*
   2  * Bitmap Module
   3  *
   4  * Stolen from linux/src/lib/bitmap.c
   5  *
   6  * Copyright (C) 2010 Corentin Chary
   7  *
   8  * This source code is licensed under the GNU General Public License,
   9  * Version 2.
  10  */
  11
  12 #include "qemu/osdep.h"
  13 #include "qemu/bitops.h"
  14 #include "qemu/bitmap.h"
  15 #include "qemu/atomic.h"
  16
  17 /*
  18  * bitmaps provide an array of bits, implemented using an
  19  * array of unsigned longs.  The number of valid bits in a
  20  * given bitmap does _not_ need to be an exact multiple of
  21  * BITS_PER_LONG.
  22  *
  23  * The possible unused bits in the last, partially used word
  24  * of a bitmap are 'don't care'.  The implementation makes
  25  * no particular effort to keep them zero.  It ensures that
  26  * their value will not affect the results of any operation.
  27  * The bitmap operations that return Boolean (bitmap_empty,
  28  * for example) or scalar (bitmap_weight, for example) results
  29  * carefully filter out these unused bits from impacting their
  30  * results.
  31  *
  32  * These operations actually hold to a slightly stronger rule:
  33  * if you don't input any bitmaps to these ops that have some
  34  * unused bits set, then they won't output any set unused bits
  35  * in output bitmaps.
  36  *
  37  * The byte ordering of bitmaps is more natural on little
  38  * endian architectures.
  39  */
  40
  41 int slow_bitmap_empty(const unsigned long *bitmap, long bits)
  42 {
  43     long k, lim = bits/BITS_PER_LONG;
  44
  45     for (k = 0; k < lim; ++k) {
  46         if (bitmap[k]) {
  47             return 0;
  48         }
  49     }
  50     if (bits % BITS_PER_LONG) {
  51         if (bitmap[k] & BITMAP_LAST_WORD_MASK(bits)) {
  52             return 0;
  53         }
  54     }
  55
  56     return 1;
  57 }
  58
  59 int slow_bitmap_full(const unsigned long *bitmap, long bits)
  60 {
  61     long k, lim = bits/BITS_PER_LONG;
  62
  63     for (k = 0; k < lim; ++k) {
  64         if (~bitmap[k]) {
  65             return 0;
  66         }
  67     }
  68
  69     if (bits % BITS_PER_LONG) {
  70         if (~bitmap[k] & BITMAP_LAST_WORD_MASK(bits)) {
  71             return 0;
  72         }
  73     }
  74
  75     return 1;
  76 }
  77
  78 int slow_bitmap_equal(const unsigned long *bitmap1,
  79                       const unsigned long *bitmap2, long bits)
  80 {
  81     long k, lim = bits/BITS_PER_LONG;
  82
  83     for (k = 0; k < lim; ++k) {
  84         if (bitmap1[k] != bitmap2[k]) {
  85             return 0;
  86         }
  87     }
  88
  89     if (bits % BITS_PER_LONG) {
  90         if ((bitmap1[k] ^ bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits)) {
  91             return 0;
  92         }
  93     }
  94
  95     return 1;
  96 }
  97
  98 void slow_bitmap_complement(unsigned long *dst, const unsigned long *src,
  99                             long bits)
 100 {
 101     long k, lim = bits/BITS_PER_LONG;
 102
 103     for (k = 0; k < lim; ++k) {
 104         dst[k] = ~src[k];
 105     }
 106
 107     if (bits % BITS_PER_LONG) {
 108         dst[k] = ~src[k] & BITMAP_LAST_WORD_MASK(bits);
 109     }
 110 }
 111
 112 int slow_bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
 113                     const unsigned long *bitmap2, long bits)
 114 {
 115     long k;
 116     long nr = BITS_TO_LONGS(bits);
 117     unsigned long result = 0;
 118
 119     for (k = 0; k < nr; k++) {
 120         result |= (dst[k] = bitmap1[k] & bitmap2[k]);
 121     }
 122     return result != 0;
 123 }
 124
 125 void slow_bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
 126                     const unsigned long *bitmap2, long bits)
 127 {
 128     long k;
 129     long nr = BITS_TO_LONGS(bits);
 130
 131     for (k = 0; k < nr; k++) {
 132         dst[k] = bitmap1[k] | bitmap2[k];
 133     }
 134 }
 135
 136 void slow_bitmap_xor(unsigned long *dst, const unsigned long *bitmap1,
 137                      const unsigned long *bitmap2, long bits)
 138 {
 139     long k;
 140     long nr = BITS_TO_LONGS(bits);
 141
 142     for (k = 0; k < nr; k++) {
 143         dst[k] = bitmap1[k] ^ bitmap2[k];
 144     }
 145 }
 146
 147 int slow_bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
 148                        const unsigned long *bitmap2, long bits)
 149 {
 150     long k;
 151     long nr = BITS_TO_LONGS(bits);
 152     unsigned long result = 0;
 153
 154     for (k = 0; k < nr; k++) {
 155         result |= (dst[k] = bitmap1[k] & ~bitmap2[k]);
 156     }
 157     return result != 0;
 158 }
 159
 160 void bitmap_set(unsigned long *map, long start, long nr)
 161 {
 162     unsigned long *p = map + BIT_WORD(start);
 163     const long size = start + nr;
 164     int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
 165     unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
 166
 167     assert(start >= 0 && nr >= 0);
 168
 169     while (nr - bits_to_set >= 0) {
 170         *p |= mask_to_set;
 171         nr -= bits_to_set;
 172         bits_to_set = BITS_PER_LONG;
 173         mask_to_set = ~0UL;
 174         p++;
 175     }
 176     if (nr) {
 177         mask_to_set &= BITMAP_LAST_WORD_MASK(size);
 178         *p |= mask_to_set;
 179     }
 180 }
 181
 182 void bitmap_set_atomic(unsigned long *map, long start, long nr)
 183 {
 184     unsigned long *p = map + BIT_WORD(start);
 185     const long size = start + nr;
 186     int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
 187     unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
 188
 189     assert(start >= 0 && nr >= 0);
 190
 191     /* First word */
 192     if (nr - bits_to_set > 0) {
 193         atomic_or(p, mask_to_set);
 194         nr -= bits_to_set;
 195         bits_to_set = BITS_PER_LONG;
 196         mask_to_set = ~0UL;
 197         p++;
 198     }
 199
 200     /* Full words */
 201     if (bits_to_set == BITS_PER_LONG) {
 202         while (nr >= BITS_PER_LONG) {
 203             *p = ~0UL;
 204             nr -= BITS_PER_LONG;
 205             p++;
 206         }
 207     }
 208
 209     /* Last word */
 210     if (nr) {
 211         mask_to_set &= BITMAP_LAST_WORD_MASK(size);
 212         atomic_or(p, mask_to_set);
 213     } else {
 214         /* If we avoided the full barrier in atomic_or(), issue a
 215          * barrier to account for the assignments in the while loop.
 216          */
 217         smp_mb();
 218     }
 219 }
 220
 221 void bitmap_clear(unsigned long *map, long start, long nr)
 222 {
 223     unsigned long *p = map + BIT_WORD(start);
 224     const long size = start + nr;
 225     int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
 226     unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
 227
 228     assert(start >= 0 && nr >= 0);
 229
 230     while (nr - bits_to_clear >= 0) {
 231         *p &= ~mask_to_clear;
 232         nr -= bits_to_clear;
 233         bits_to_clear = BITS_PER_LONG;
 234         mask_to_clear = ~0UL;
 235         p++;
 236     }
 237     if (nr) {
 238         mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
 239         *p &= ~mask_to_clear;
 240     }
 241 }
 242
 243 bool bitmap_test_and_clear_atomic(unsigned long *map, long start, long nr)
 244 {
 245     unsigned long *p = map + BIT_WORD(start);
 246     const long size = start + nr;
 247     int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
 248     unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
 249     unsigned long dirty = 0;
 250     unsigned long old_bits;
 251
 252     assert(start >= 0 && nr >= 0);
 253
 254     /* First word */
 255     if (nr - bits_to_clear > 0) {
 256         old_bits = atomic_fetch_and(p, ~mask_to_clear);
 257         dirty |= old_bits & mask_to_clear;
 258         nr -= bits_to_clear;
 259         bits_to_clear = BITS_PER_LONG;
 260         mask_to_clear = ~0UL;
 261         p++;
 262     }
 263
 264     /* Full words */
 265     if (bits_to_clear == BITS_PER_LONG) {
 266         while (nr >= BITS_PER_LONG) {
 267             if (*p) {
 268                 old_bits = atomic_xchg(p, 0);
 269                 dirty |= old_bits;
 270             }
 271             nr -= BITS_PER_LONG;
 272             p++;
 273         }
 274     }
 275
 276     /* Last word */
 277     if (nr) {
 278         mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
 279         old_bits = atomic_fetch_and(p, ~mask_to_clear);
 280         dirty |= old_bits & mask_to_clear;
 281     } else {
 282         if (!dirty) {
 283             smp_mb();
 284         }
 285     }
 286
 287     return dirty != 0;
 288 }
 289
 290 #define ALIGN_MASK(x,mask)      (((x)+(mask))&~(mask))
 291
 292 /**
 293  * bitmap_find_next_zero_area - find a contiguous aligned zero area
 294  * @map: The address to base the search on
 295  * @size: The bitmap size in bits
 296  * @start: The bitnumber to start searching at
 297  * @nr: The number of zeroed bits we're looking for
 298  * @align_mask: Alignment mask for zero area
 299  *
 300  * The @align_mask should be one less than a power of 2; the effect is that
 301  * the bit offset of all zero areas this function finds is multiples of that
 302  * power of 2. A @align_mask of 0 means no alignment is required.
 303  */
 304 unsigned long bitmap_find_next_zero_area(unsigned long *map,
 305                                          unsigned long size,
 306                                          unsigned long start,
 307                                          unsigned long nr,
 308                                          unsigned long align_mask)
 309 {
 310     unsigned long index, end, i;
 311 again:
 312     index = find_next_zero_bit(map, size, start);
 313
 314     /* Align allocation */
 315     index = ALIGN_MASK(index, align_mask);
 316
 317     end = index + nr;
 318     if (end > size) {
 319         return end;
 320     }
 321     i = find_next_bit(map, end, index);
 322     if (i < end) {
 323         start = i + 1;
 324         goto again;
 325     }
 326     return index;
 327 }
 328
 329 int slow_bitmap_intersects(const unsigned long *bitmap1,
 330                            const unsigned long *bitmap2, long bits)
 331 {
 332     long k, lim = bits/BITS_PER_LONG;
 333
 334     for (k = 0; k < lim; ++k) {
 335         if (bitmap1[k] & bitmap2[k]) {
 336             return 1;
 337         }
 338     }
 339
 340     if (bits % BITS_PER_LONG) {
 341         if ((bitmap1[k] & bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits)) {
 342             return 1;
 343         }
 344     }
 345     return 0;
 346 }