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 "replace.h"
  21 #include <talloc.h>
  22 #include "lib/util/bitmap.h"
  23 #include "lib/util/debug.h"
  24 #include "lib/util/fault.h"
  25
  26 struct bitmap {
  27         unsigned int n;
  28         uint32_t b[1];          /* We allocate more */
  29 };
  30
  31 /* these functions provide a simple way to allocate integers from a
  32    pool without repetition */
  33
  34 /****************************************************************************
  35 talloc a bitmap
  36 ****************************************************************************/
  37 struct bitmap *bitmap_talloc(TALLOC_CTX *mem_ctx, int n)
  38 {
  39         struct bitmap *bm;
  40
  41         bm = (struct bitmap *)talloc_zero_size(
  42                 mem_ctx,
  43                 offsetof(struct bitmap, b) + sizeof(uint32_t)*((n+31)/32));
  44
  45         if (!bm) return NULL;
  46
  47         talloc_set_name_const(bm, "struct bitmap");
  48
  49         bm->n = n;
  50         return bm;
  51 }
  52
  53 /****************************************************************************
  54 copy as much of the source bitmap as will fit in the destination bitmap.
  55 ****************************************************************************/
  56
  57 int bitmap_copy(struct bitmap * const dst, const struct bitmap * const src)
  58 {
  59         int count = MIN(dst->n, src->n);
  60
  61         SMB_ASSERT(dst->b != src->b);
  62         memcpy(dst->b, src->b, sizeof(uint32_t)*((count+31)/32));
  63
  64         return count;
  65 }
  66
  67 /****************************************************************************
  68 set a bit in a bitmap
  69 ****************************************************************************/
  70 bool bitmap_set(struct bitmap *bm, unsigned i)
  71 {
  72         if (i >= bm->n) {
  73                 DEBUG(0,("Setting invalid bitmap entry %d (of %d)\n",
  74                       i, bm->n));
  75                 return false;
  76         }
  77         bm->b[i/32] |= (1U<<(i%32));
  78         return true;
  79 }
  80
  81 /****************************************************************************
  82 clear a bit in a bitmap
  83 ****************************************************************************/
  84 bool bitmap_clear(struct bitmap *bm, unsigned i)
  85 {
  86         if (i >= bm->n) {
  87                 DEBUG(0,("clearing invalid bitmap entry %d (of %d)\n",
  88                       i, bm->n));
  89                 return false;
  90         }
  91         bm->b[i/32] &= ~(1U<<(i%32));
  92         return true;
  93 }
  94
  95 /****************************************************************************
  96 query a bit in a bitmap
  97 ****************************************************************************/
  98 bool bitmap_query(struct bitmap *bm, unsigned i)
  99 {
 100         if (i >= bm->n) return false;
 101         if (bm->b[i/32] & (1U<<(i%32))) {
 102                 return true;
 103         }
 104         return false;
 105 }
 106
 107 /****************************************************************************
 108 find a zero bit in a bitmap starting at the specified offset, with
 109 wraparound
 110 ****************************************************************************/
 111 int bitmap_find(struct bitmap *bm, unsigned ofs)
 112 {
 113         unsigned int i, j;
 114
 115         if (ofs > bm->n) ofs = 0;
 116
 117         i = ofs;
 118         while (i < bm->n) {
 119                 if (~(bm->b[i/32])) {
 120                         j = i;
 121                         do {
 122                                 if (!bitmap_query(bm, j)) return j;
 123                                 j++;
 124                         } while (j & 31 && j < bm->n);
 125                 }
 126                 i += 32;
 127                 i &= ~31;
 128         }
 129
 130         i = 0;
 131         while (i < ofs) {
 132                 if (~(bm->b[i/32])) {
 133                         j = i;
 134                         do {
 135                                 if (!bitmap_query(bm, j)) return j;
 136                                 j++;
 137                         } while (j & 31 && j < bm->n);
 138                 }
 139                 i += 32;
 140                 i &= ~31;
 141         }
 142
 143         return -1;
 144 }