source/lib/bitmap.c

   1 /*
   2    Unix SMB/Netbios implementation.
   3    Version 1.9.
   4    simple bitmap functions
   5    Copyright (C) Andrew Tridgell 1992-1998
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20 */
  21
  22 #include "includes.h"
  23
  24 /* these functions provide a simple way to allocate integers from a
  25    pool without repitition */
  26
  27
  28 /****************************************************************************
  29 allocate a bitmap of the specified size
  30 ****************************************************************************/
  31 struct bitmap *bitmap_allocate(int n)
  32 {
  33         struct bitmap *bm;
  34
  35         bm = (struct bitmap *)malloc(sizeof(*bm));
  36
  37         if (!bm) return NULL;
  38
  39         bm->n = n;
  40         bm->b = (uint32 *)malloc(sizeof(bm->b[0])*(n+31)/32);
  41         if (!bm->b) {
  42                 SAFE_FREE(bm);
  43                 return NULL;
  44         }
  45
  46         memset(bm->b, 0, sizeof(bm->b[0])*(n+31)/32);
  47
  48         return bm;
  49 }
  50
  51 /****************************************************************************
  52 free a bitmap.
  53 ****************************************************************************/
  54
  55 void bitmap_free(struct bitmap *bm)
  56 {
  57         if (!bm)
  58                 return;
  59
  60         SAFE_FREE(bm->b);
  61         SAFE_FREE(bm);
  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         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 }