lib/util/bitmap.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    simple bitmap functions
   4    Copyright (C) Andrew Tridgell 1992-1998
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #include "includes.h"
  21 #include "lib/util/bitmap.h"
  22
  23 struct bitmap {
  24         uint32_t *b;
  25         unsigned int n;
  26 };
  27
  28 /* these functions provide a simple way to allocate integers from a
  29    pool without repetition */
  30
  31 /****************************************************************************
  32 talloc a bitmap
  33 ****************************************************************************/
  34 struct bitmap *bitmap_talloc(TALLOC_CTX *mem_ctx, int n)
  35 {
  36         struct bitmap *bm;
  37
  38         bm = talloc(mem_ctx, struct bitmap);
  39
  40         if (!bm) return NULL;
  41
  42         bm->n = n;
  43         bm->b = talloc_zero_array(bm, uint32_t, (n+31)/32);
  44         if (!bm->b) {
  45                 TALLOC_FREE(bm);
  46                 return NULL;
  47         }
  48         return bm;
  49 }
  50
  51 /****************************************************************************
  52 copy as much of the source bitmap as will fit in the destination bitmap.
  53 ****************************************************************************/
  54
  55 int bitmap_copy(struct bitmap * const dst, const struct bitmap * const src)
  56 {
  57         int count = MIN(dst->n, src->n);
  58
  59         SMB_ASSERT(dst->b != src->b);
  60         memcpy(dst->b, src->b, sizeof(uint32_t)*((count+31)/32));
  61
  62         return count;
  63 }
  64
  65 /****************************************************************************
  66 set a bit in a bitmap
  67 ****************************************************************************/
  68 bool bitmap_set(struct bitmap *bm, unsigned i)
  69 {
  70         if (i >= bm->n) {
  71                 DEBUG(0,("Setting invalid bitmap entry %d (of %d)\n",
  72                       i, bm->n));
  73                 return false;
  74         }
  75         bm->b[i/32] |= (1<<(i%32));
  76         return true;
  77 }
  78
  79 /****************************************************************************
  80 clear a bit in a bitmap
  81 ****************************************************************************/
  82 bool bitmap_clear(struct bitmap *bm, unsigned i)
  83 {
  84         if (i >= bm->n) {
  85                 DEBUG(0,("clearing invalid bitmap entry %d (of %d)\n",
  86                       i, bm->n));
  87                 return false;
  88         }
  89         bm->b[i/32] &= ~(1<<(i%32));
  90         return true;
  91 }
  92
  93 /****************************************************************************
  94 query a bit in a bitmap
  95 ****************************************************************************/
  96 bool bitmap_query(struct bitmap *bm, unsigned i)
  97 {
  98         if (i >= bm->n) return false;
  99         if (bm->b[i/32] & (1<<(i%32))) {
 100                 return true;
 101         }
 102         return false;
 103 }
 104
 105 /****************************************************************************
 106 find a zero bit in a bitmap starting at the specified offset, with
 107 wraparound
 108 ****************************************************************************/
 109 int bitmap_find(struct bitmap *bm, unsigned ofs)
 110 {
 111         unsigned int i, j;
 112
 113         if (ofs > bm->n) ofs = 0;
 114
 115         i = ofs;
 116         while (i < bm->n) {
 117                 if (~(bm->b[i/32])) {
 118                         j = i;
 119                         do {
 120                                 if (!bitmap_query(bm, j)) return j;
 121                                 j++;
 122                         } while (j & 31 && j < bm->n);
 123                 }
 124                 i += 32;
 125                 i &= ~31;
 126         }
 127
 128         i = 0;
 129         while (i < ofs) {
 130                 if (~(bm->b[i/32])) {
 131                         j = i;
 132                         do {
 133                                 if (!bitmap_query(bm, j)) return j;
 134                                 j++;
 135                         } while (j & 31 && j < bm->n);
 136                 }
 137                 i += 32;
 138                 i &= ~31;
 139         }
 140
 141         return -1;
 142 }