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 "bitops.h"
  13 #include "bitmap.h"
  14
  15 /*
  16  * bitmaps provide an array of bits, implemented using an an
  17  * array of unsigned longs.  The number of valid bits in a
  18  * given bitmap does _not_ need to be an exact multiple of
  19  * BITS_PER_LONG.
  20  *
  21  * The possible unused bits in the last, partially used word
  22  * of a bitmap are 'don't care'.  The implementation makes
  23  * no particular effort to keep them zero.  It ensures that
  24  * their value will not affect the results of any operation.
  25  * The bitmap operations that return Boolean (bitmap_empty,
  26  * for example) or scalar (bitmap_weight, for example) results
  27  * carefully filter out these unused bits from impacting their
  28  * results.
  29  *
  30  * These operations actually hold to a slightly stronger rule:
  31  * if you don't input any bitmaps to these ops that have some
  32  * unused bits set, then they won't output any set unused bits
  33  * in output bitmaps.
  34  *
  35  * The byte ordering of bitmaps is more natural on little
  36  * endian architectures.
  37  */
  38
  39 int slow_bitmap_empty(const unsigned long *bitmap, int bits)
  40 {
  41     int k, lim = bits/BITS_PER_LONG;
  42
  43     for (k = 0; k < lim; ++k) {
  44         if (bitmap[k]) {
  45             return 0;
  46         }
  47     }
  48     if (bits % BITS_PER_LONG) {
  49         if (bitmap[k] & BITMAP_LAST_WORD_MASK(bits)) {
  50             return 0;
  51         }
  52     }
  53
  54     return 1;
  55 }
  56
  57 int slow_bitmap_full(const unsigned long *bitmap, int bits)
  58 {
  59     int k, lim = bits/BITS_PER_LONG;
  60
  61     for (k = 0; k < lim; ++k) {
  62         if (~bitmap[k]) {
  63             return 0;
  64         }
  65     }
  66
  67     if (bits % BITS_PER_LONG) {
  68         if (~bitmap[k] & BITMAP_LAST_WORD_MASK(bits)) {
  69             return 0;
  70         }
  71     }
  72
  73     return 1;
  74 }
  75
  76 int slow_bitmap_equal(const unsigned long *bitmap1,
  77                       const unsigned long *bitmap2, int bits)
  78 {
  79     int k, lim = bits/BITS_PER_LONG;
  80
  81     for (k = 0; k < lim; ++k) {
  82         if (bitmap1[k] != bitmap2[k]) {
  83             return 0;
  84         }
  85     }
  86
  87     if (bits % BITS_PER_LONG) {
  88         if ((bitmap1[k] ^ bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits)) {
  89             return 0;
  90         }
  91     }
  92
  93     return 1;
  94 }
  95
  96 void slow_bitmap_complement(unsigned long *dst, const unsigned long *src,
  97                             int bits)
  98 {
  99     int k, lim = bits/BITS_PER_LONG;
 100
 101     for (k = 0; k < lim; ++k) {
 102         dst[k] = ~src[k];
 103     }
 104
 105     if (bits % BITS_PER_LONG) {
 106         dst[k] = ~src[k] & BITMAP_LAST_WORD_MASK(bits);
 107     }
 108 }
 109
 110 int slow_bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
 111                     const unsigned long *bitmap2, int bits)
 112 {
 113     int k;
 114     int nr = BITS_TO_LONGS(bits);
 115     unsigned long result = 0;
 116
 117     for (k = 0; k < nr; k++) {
 118         result |= (dst[k] = bitmap1[k] & bitmap2[k]);
 119     }
 120     return result != 0;
 121 }
 122
 123 void slow_bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
 124                     const unsigned long *bitmap2, int bits)
 125 {
 126     int k;
 127     int nr = BITS_TO_LONGS(bits);
 128
 129     for (k = 0; k < nr; k++) {
 130         dst[k] = bitmap1[k] | bitmap2[k];
 131     }
 132 }
 133
 134 void slow_bitmap_xor(unsigned long *dst, const unsigned long *bitmap1,
 135                      const unsigned long *bitmap2, int bits)
 136 {
 137     int k;
 138     int nr = BITS_TO_LONGS(bits);
 139
 140     for (k = 0; k < nr; k++) {
 141         dst[k] = bitmap1[k] ^ bitmap2[k];
 142     }
 143 }
 144
 145 int slow_bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
 146                        const unsigned long *bitmap2, int bits)
 147 {
 148     int k;
 149     int nr = BITS_TO_LONGS(bits);
 150     unsigned long result = 0;
 151
 152     for (k = 0; k < nr; k++) {
 153         result |= (dst[k] = bitmap1[k] & ~bitmap2[k]);
 154     }
 155     return result != 0;
 156 }
 157
 158 #define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) % BITS_PER_LONG))
 159
 160 void bitmap_set(unsigned long *map, int start, int nr)
 161 {
 162     unsigned long *p = map + BIT_WORD(start);
 163     const int 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     while (nr - bits_to_set >= 0) {
 168         *p |= mask_to_set;
 169         nr -= bits_to_set;
 170         bits_to_set = BITS_PER_LONG;
 171         mask_to_set = ~0UL;
 172         p++;
 173     }
 174     if (nr) {
 175         mask_to_set &= BITMAP_LAST_WORD_MASK(size);
 176         *p |= mask_to_set;
 177     }
 178 }
 179
 180 void bitmap_clear(unsigned long *map, int start, int nr)
 181 {
 182     unsigned long *p = map + BIT_WORD(start);
 183     const int size = start + nr;
 184     int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
 185     unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
 186
 187     while (nr - bits_to_clear >= 0) {
 188         *p &= ~mask_to_clear;
 189         nr -= bits_to_clear;
 190         bits_to_clear = BITS_PER_LONG;
 191         mask_to_clear = ~0UL;
 192         p++;
 193     }
 194     if (nr) {
 195         mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
 196         *p &= ~mask_to_clear;
 197     }
 198 }
 199
 200 #define ALIGN_MASK(x,mask)      (((x)+(mask))&~(mask))
 201
 202 /**
 203  * bitmap_find_next_zero_area - find a contiguous aligned zero area
 204  * @map: The address to base the search on
 205  * @size: The bitmap size in bits
 206  * @start: The bitnumber to start searching at
 207  * @nr: The number of zeroed bits we're looking for
 208  * @align_mask: Alignment mask for zero area
 209  *
 210  * The @align_mask should be one less than a power of 2; the effect is that
 211  * the bit offset of all zero areas this function finds is multiples of that
 212  * power of 2. A @align_mask of 0 means no alignment is required.
 213  */
 214 unsigned long bitmap_find_next_zero_area(unsigned long *map,
 215                                          unsigned long size,
 216                                          unsigned long start,
 217                                          unsigned int nr,
 218                                          unsigned long align_mask)
 219 {
 220     unsigned long index, end, i;
 221 again:
 222     index = find_next_zero_bit(map, size, start);
 223
 224     /* Align allocation */
 225     index = ALIGN_MASK(index, align_mask);
 226
 227     end = index + nr;
 228     if (end > size) {
 229         return end;
 230     }
 231     i = find_next_bit(map, end, index);
 232     if (i < end) {
 233         start = i + 1;
 234         goto again;
 235     }
 236     return index;
 237 }
 238
 239 int slow_bitmap_intersects(const unsigned long *bitmap1,
 240                            const unsigned long *bitmap2, int bits)
 241 {
 242     int k, lim = bits/BITS_PER_LONG;
 243
 244     for (k = 0; k < lim; ++k) {
 245         if (bitmap1[k] & bitmap2[k]) {
 246             return 1;
 247         }
 248     }
 249
 250     if (bits % BITS_PER_LONG) {
 251         if ((bitmap1[k] & bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits)) {
 252             return 1;
 253         }
 254     }
 255     return 0;
 256 }