src/basic/bitmap.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2015 Tom Gundersen
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include "util.h"
  23
  24 #include "bitmap.h"
  25
  26 struct Bitmap {
  27         uint64_t *bitmaps;
  28         size_t n_bitmaps;
  29         size_t bitmaps_allocated;
  30 };
  31
  32 /* Bitmaps are only meant to store relatively small numbers
  33  * (corresponding to, say, an enum), so it is ok to limit
  34  * the max entry. 64k should be plenty. */
  35 #define BITMAPS_MAX_ENTRY 0xffff
  36
  37 /* This indicates that we reached the end of the bitmap */
  38 #define BITMAP_END ((unsigned) -1)
  39
  40 #define BITMAP_NUM_TO_OFFSET(n)           ((n) / (sizeof(uint64_t) * 8))
  41 #define BITMAP_NUM_TO_REM(n)              ((n) % (sizeof(uint64_t) * 8))
  42 #define BITMAP_OFFSET_TO_NUM(offset, rem) ((offset) * sizeof(uint64_t) * 8 + (rem))
  43
  44 Bitmap *bitmap_new(void) {
  45         return new0(Bitmap, 1);
  46 }
  47
  48 void bitmap_free(Bitmap *b) {
  49         if (!b)
  50                 return;
  51
  52         free(b->bitmaps);
  53         free(b);
  54 }
  55
  56 int bitmap_ensure_allocated(Bitmap **b) {
  57         Bitmap *a;
  58
  59         assert(b);
  60
  61         if (*b)
  62                 return 0;
  63
  64         a = bitmap_new();
  65         if (!a)
  66                 return -ENOMEM;
  67
  68         *b = a;
  69
  70         return 0;
  71 }
  72
  73 int bitmap_set(Bitmap *b, unsigned n) {
  74         uint64_t bitmask;
  75         unsigned offset;
  76
  77         assert(b);
  78
  79         /* we refuse to allocate huge bitmaps */
  80         if (n > BITMAPS_MAX_ENTRY)
  81                 return -ERANGE;
  82
  83         offset = BITMAP_NUM_TO_OFFSET(n);
  84
  85         if (offset >= b->n_bitmaps) {
  86                 if (!GREEDY_REALLOC0(b->bitmaps, b->bitmaps_allocated, offset + 1))
  87                         return -ENOMEM;
  88
  89                 b->n_bitmaps = offset + 1;
  90         }
  91
  92         bitmask = UINT64_C(1) << BITMAP_NUM_TO_REM(n);
  93
  94         b->bitmaps[offset] |= bitmask;
  95
  96         return 0;
  97 }
  98
  99 void bitmap_unset(Bitmap *b, unsigned n) {
 100         uint64_t bitmask;
 101         unsigned offset;
 102
 103         if (!b)
 104                 return;
 105
 106         offset = BITMAP_NUM_TO_OFFSET(n);
 107
 108         if (offset >= b->n_bitmaps)
 109                 return;
 110
 111         bitmask = UINT64_C(1) << BITMAP_NUM_TO_REM(n);
 112
 113         b->bitmaps[offset] &= ~bitmask;
 114 }
 115
 116 bool bitmap_isset(Bitmap *b, unsigned n) {
 117         uint64_t bitmask;
 118         unsigned offset;
 119
 120         if (!b)
 121                 return false;
 122
 123         offset = BITMAP_NUM_TO_OFFSET(n);
 124
 125         if (offset >= b->n_bitmaps)
 126                 return false;
 127
 128         bitmask = UINT64_C(1) << BITMAP_NUM_TO_REM(n);
 129
 130         return !!(b->bitmaps[offset] & bitmask);
 131 }
 132
 133 bool bitmap_isclear(Bitmap *b) {
 134         unsigned i;
 135
 136         assert(b);
 137
 138         for (i = 0; i < b->n_bitmaps; i++)
 139                 if (b->bitmaps[i] != 0)
 140                         return false;
 141
 142         return true;
 143 }
 144
 145 void bitmap_clear(Bitmap *b) {
 146         assert(b);
 147
 148         b->n_bitmaps = 0;
 149 }
 150
 151 bool bitmap_iterate(Bitmap *b, Iterator *i, unsigned *n) {
 152         uint64_t bitmask;
 153         unsigned offset, rem;
 154
 155         assert(i);
 156         assert(n);
 157
 158         if (!b || i->idx == BITMAP_END)
 159                 return false;
 160
 161         offset = BITMAP_NUM_TO_OFFSET(i->idx);
 162         rem = BITMAP_NUM_TO_REM(i->idx);
 163         bitmask = UINT64_C(1) << rem;
 164
 165         for (; offset < b->n_bitmaps; offset ++) {
 166                 if (b->bitmaps[offset]) {
 167                         for (; bitmask; bitmask <<= 1, rem ++) {
 168                                 if (b->bitmaps[offset] & bitmask) {
 169                                         *n = BITMAP_OFFSET_TO_NUM(offset, rem);
 170                                         i->idx = *n + 1;
 171
 172                                         return true;
 173                                 }
 174                         }
 175                 }
 176
 177                 rem = 0;
 178                 bitmask = 1;
 179         }
 180
 181         i->idx = BITMAP_END;
 182
 183         return false;
 184 }
 185
 186 bool bitmap_equal(Bitmap *a, Bitmap *b) {
 187
 188         if (!a ^ !b)
 189                 return false;
 190
 191         if (!a)
 192                 return true;
 193
 194         if (a->n_bitmaps != b->n_bitmaps)
 195                 return false;
 196
 197         return memcmp(a->bitmaps, b->bitmaps, sizeof(uint64_t) * a->n_bitmaps) == 0;
 198 }