source3/lib/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
  22 /* these functions provide a simple way to allocate integers from a
  23    pool without repetition */
  24
  25 /****************************************************************************
  26 talloc a bitmap
  27 ****************************************************************************/
  28 struct bitmap *bitmap_talloc(TALLOC_CTX *mem_ctx, int n)
  29 {
  30         struct bitmap *bm;
  31
  32         bm = talloc(mem_ctx, struct bitmap);
  33
  34         if (!bm) return NULL;
  35
  36         bm->n = n;
  37         bm->b = talloc_zero_array(bm, uint32, (n+31)/32);
  38         if (!bm->b) {
  39                 TALLOC_FREE(bm);
  40                 return NULL;
  41         }
  42         return bm;
  43 }
  44
  45 /****************************************************************************
  46 copy as much of the source bitmap as will fit in the destination bitmap.
  47 ****************************************************************************/
  48
  49 int bitmap_copy(struct bitmap * const dst, const struct bitmap * const src)
  50 {
  51         int count = MIN(dst->n, src->n);
  52
  53         SMB_ASSERT(dst->b != src->b);
  54         memcpy(dst->b, src->b, sizeof(uint32)*((count+31)/32));
  55
  56         return count;
  57 }
  58
  59 /****************************************************************************
  60 set a bit in a bitmap
  61 ****************************************************************************/
  62 bool bitmap_set(struct bitmap *bm, unsigned i)
  63 {
  64         if (i >= bm->n) {
  65                 DEBUG(0,("Setting invalid bitmap entry %d (of %d)\n",
  66                       i, bm->n));
  67                 return False;
  68         }
  69         bm->b[i/32] |= (1<<(i%32));
  70         return True;
  71 }
  72
  73 /****************************************************************************
  74 clear a bit in a bitmap
  75 ****************************************************************************/
  76 bool bitmap_clear(struct bitmap *bm, unsigned i)
  77 {
  78         if (i >= bm->n) {
  79                 DEBUG(0,("clearing invalid bitmap entry %d (of %d)\n",
  80                       i, bm->n));
  81                 return False;
  82         }
  83         bm->b[i/32] &= ~(1<<(i%32));
  84         return True;
  85 }
  86
  87 /****************************************************************************
  88 query a bit in a bitmap
  89 ****************************************************************************/
  90 bool bitmap_query(struct bitmap *bm, unsigned i)
  91 {
  92         if (i >= bm->n) return False;
  93         if (bm->b[i/32] & (1<<(i%32))) {
  94                 return True;
  95         }
  96         return False;
  97 }
  98
  99 /****************************************************************************
 100 find a zero bit in a bitmap starting at the specified offset, with
 101 wraparound
 102 ****************************************************************************/
 103 int bitmap_find(struct bitmap *bm, unsigned ofs)
 104 {
 105         unsigned int i, j;
 106
 107         if (ofs > bm->n) ofs = 0;
 108
 109         i = ofs;
 110         while (i < bm->n) {
 111                 if (~(bm->b[i/32])) {
 112                         j = i;
 113                         do {
 114                                 if (!bitmap_query(bm, j)) return j;
 115                                 j++;
 116                         } while (j & 31 && j < bm->n);
 117                 }
 118                 i += 32;
 119                 i &= ~31;
 120         }
 121
 122         i = 0;
 123         while (i < ofs) {
 124                 if (~(bm->b[i/32])) {
 125                         j = i;
 126                         do {
 127                                 if (!bitmap_query(bm, j)) return j;
 128                                 j++;
 129                         } while (j & 31 && j < bm->n);
 130                 }
 131                 i += 32;
 132                 i &= ~31;
 133         }
 134
 135         return -1;
 136 }