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 <errno.h>
  23 #include <stddef.h>
  24 #include <stdint.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27
  28 #include "alloc-util.h"
  29 #include "bitmap.h"
  30 #include "hashmap.h"
  31 #include "macro.h"
  32
  33 struct Bitmap {
  34         uint64_t *bitmaps;
  35         size_t n_bitmaps;
  36         size_t bitmaps_allocated;
  37 };
  38
  39 /* Bitmaps are only meant to store relatively small numbers
  40  * (corresponding to, say, an enum), so it is ok to limit
  41  * the max entry. 64k should be plenty. */
  42 #define BITMAPS_MAX_ENTRY 0xffff
  43
  44 /* This indicates that we reached the end of the bitmap */
  45 #define BITMAP_END ((unsigned) -1)
  46
  47 #define BITMAP_NUM_TO_OFFSET(n)           ((n) / (sizeof(uint64_t) * 8))
  48 #define BITMAP_NUM_TO_REM(n)              ((n) % (sizeof(uint64_t) * 8))
  49 #define BITMAP_OFFSET_TO_NUM(offset, rem) ((offset) * sizeof(uint64_t) * 8 + (rem))
  50
  51 Bitmap *bitmap_new(void) {
  52         return new0(Bitmap, 1);
  53 }
  54
  55 void bitmap_free(Bitmap *b) {
  56         if (!b)
  57                 return;
  58
  59         free(b->bitmaps);
  60         free(b);
  61 }
  62
  63 int bitmap_ensure_allocated(Bitmap **b) {
  64         Bitmap *a;
  65
  66         assert(b);
  67
  68         if (*b)
  69                 return 0;
  70
  71         a = bitmap_new();
  72         if (!a)
  73                 return -ENOMEM;
  74
  75         *b = a;
  76
  77         return 0;
  78 }
  79
  80 int bitmap_set(Bitmap *b, unsigned n) {
  81         uint64_t bitmask;
  82         unsigned offset;
  83
  84         assert(b);
  85
  86         /* we refuse to allocate huge bitmaps */
  87         if (n > BITMAPS_MAX_ENTRY)
  88                 return -ERANGE;
  89
  90         offset = BITMAP_NUM_TO_OFFSET(n);
  91
  92         if (offset >= b->n_bitmaps) {
  93                 if (!GREEDY_REALLOC0(b->bitmaps, b->bitmaps_allocated, offset + 1))
  94                         return -ENOMEM;
  95
  96                 b->n_bitmaps = offset + 1;
  97         }
  98
  99         bitmask = UINT64_C(1) << BITMAP_NUM_TO_REM(n);
 100
 101         b->bitmaps[offset] |= bitmask;
 102
 103         return 0;
 104 }
 105
 106 void bitmap_unset(Bitmap *b, unsigned n) {
 107         uint64_t bitmask;
 108         unsigned offset;
 109
 110         if (!b)
 111                 return;
 112
 113         offset = BITMAP_NUM_TO_OFFSET(n);
 114
 115         if (offset >= b->n_bitmaps)
 116                 return;
 117
 118         bitmask = UINT64_C(1) << BITMAP_NUM_TO_REM(n);
 119
 120         b->bitmaps[offset] &= ~bitmask;
 121 }
 122
 123 bool bitmap_isset(Bitmap *b, unsigned n) {
 124         uint64_t bitmask;
 125         unsigned offset;
 126
 127         if (!b)
 128                 return false;
 129
 130         offset = BITMAP_NUM_TO_OFFSET(n);
 131
 132         if (offset >= b->n_bitmaps)
 133                 return false;
 134
 135         bitmask = UINT64_C(1) << BITMAP_NUM_TO_REM(n);
 136
 137         return !!(b->bitmaps[offset] & bitmask);
 138 }
 139
 140 bool bitmap_isclear(Bitmap *b) {
 141         unsigned i;
 142
 143         assert(b);
 144
 145         for (i = 0; i < b->n_bitmaps; i++)
 146                 if (b->bitmaps[i] != 0)
 147                         return false;
 148
 149         return true;
 150 }
 151
 152 void bitmap_clear(Bitmap *b) {
 153         assert(b);
 154
 155         b->bitmaps = mfree(b->bitmaps);
 156         b->n_bitmaps = 0;
 157         b->bitmaps_allocated = 0;
 158 }
 159
 160 bool bitmap_iterate(Bitmap *b, Iterator *i, unsigned *n) {
 161         uint64_t bitmask;
 162         unsigned offset, rem;
 163
 164         assert(i);
 165         assert(n);
 166
 167         if (!b || i->idx == BITMAP_END)
 168                 return false;
 169
 170         offset = BITMAP_NUM_TO_OFFSET(i->idx);
 171         rem = BITMAP_NUM_TO_REM(i->idx);
 172         bitmask = UINT64_C(1) << rem;
 173
 174         for (; offset < b->n_bitmaps; offset ++) {
 175                 if (b->bitmaps[offset]) {
 176                         for (; bitmask; bitmask <<= 1, rem ++) {
 177                                 if (b->bitmaps[offset] & bitmask) {
 178                                         *n = BITMAP_OFFSET_TO_NUM(offset, rem);
 179                                         i->idx = *n + 1;
 180
 181                                         return true;
 182                                 }
 183                         }
 184                 }
 185
 186                 rem = 0;
 187                 bitmask = 1;
 188         }
 189
 190         i->idx = BITMAP_END;
 191
 192         return false;
 193 }
 194
 195 bool bitmap_equal(Bitmap *a, Bitmap *b) {
 196         size_t common_n_bitmaps;
 197         Bitmap *c;
 198         unsigned i;
 199
 200         if (!a ^ !b)
 201                 return false;
 202
 203         if (!a)
 204                 return true;
 205
 206         common_n_bitmaps = MIN(a->n_bitmaps, b->n_bitmaps);
 207         if (memcmp(a->bitmaps, b->bitmaps, sizeof(uint64_t) * common_n_bitmaps) != 0)
 208                 return false;
 209
 210         c = a->n_bitmaps > b->n_bitmaps ? a : b;
 211         for (i = common_n_bitmaps; i < c->n_bitmaps; i++)
 212                 if (c->bitmaps[i] != 0)
 213                         return false;
 214
 215         return true;
 216 }