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         unsigned int n;
  25         uint32_t b[1];          /* We allocate more */
  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 = (struct bitmap *)talloc_zero_size(
  39                 mem_ctx,
  40                 offsetof(struct bitmap, b) + sizeof(uint32_t)*((n+31)/32));
  41
  42         if (!bm) return NULL;
  43
  44         talloc_set_name_const(bm, "struct bitmap");
  45
  46         bm->n = n;
  47         return bm;
  48 }
  49
  50 /****************************************************************************
  51 copy as much of the source bitmap as will fit in the destination bitmap.
  52 ****************************************************************************/
  53
  54 int bitmap_copy(struct bitmap * const dst, const struct bitmap * const src)
  55 {
  56         int count = MIN(dst->n, src->n);
  57
  58         SMB_ASSERT(dst->b != src->b);
  59         memcpy(dst->b, src->b, sizeof(uint32_t)*((count+31)/32));
  60
  61         return count;
  62 }
  63
  64 /****************************************************************************
  65 set a bit in a bitmap
  66 ****************************************************************************/
  67 bool bitmap_set(struct bitmap *bm, unsigned i)
  68 {
  69         if (i >= bm->n) {
  70                 DEBUG(0,("Setting invalid bitmap entry %d (of %d)\n",
  71                       i, bm->n));
  72                 return false;
  73         }
  74         bm->b[i/32] |= (1<<(i%32));
  75         return true;
  76 }
  77
  78 /****************************************************************************
  79 clear a bit in a bitmap
  80 ****************************************************************************/
  81 bool bitmap_clear(struct bitmap *bm, unsigned i)
  82 {
  83         if (i >= bm->n) {
  84                 DEBUG(0,("clearing invalid bitmap entry %d (of %d)\n",
  85                       i, bm->n));
  86                 return false;
  87         }
  88         bm->b[i/32] &= ~(1<<(i%32));
  89         return true;
  90 }
  91
  92 /****************************************************************************
  93 query a bit in a bitmap
  94 ****************************************************************************/
  95 bool bitmap_query(struct bitmap *bm, unsigned i)
  96 {
  97         if (i >= bm->n) return false;
  98         if (bm->b[i/32] & (1<<(i%32))) {
  99                 return true;
 100         }
 101         return false;
 102 }
 103
 104 /****************************************************************************
 105 find a zero bit in a bitmap starting at the specified offset, with
 106 wraparound
 107 ****************************************************************************/
 108 int bitmap_find(struct bitmap *bm, unsigned ofs)
 109 {
 110         unsigned int i, j;
 111
 112         if (ofs > bm->n) ofs = 0;
 113
 114         i = ofs;
 115         while (i < bm->n) {
 116                 if (~(bm->b[i/32])) {
 117                         j = i;
 118                         do {
 119                                 if (!bitmap_query(bm, j)) return j;
 120                                 j++;
 121                         } while (j & 31 && j < bm->n);
 122                 }
 123                 i += 32;
 124                 i &= ~31;
 125         }
 126
 127         i = 0;
 128         while (i < ofs) {
 129                 if (~(bm->b[i/32])) {
 130                         j = i;
 131                         do {
 132                                 if (!bitmap_query(bm, j)) return j;
 133                                 j++;
 134                         } while (j & 31 && j < bm->n);
 135                 }
 136                 i += 32;
 137                 i &= ~31;
 138         }
 139
 140         return -1;
 141 }