source/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 2 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, write to the Free Software
  18    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19 */
  20
  21 #include "includes.h"
  22
  23 /* these functions provide a simple way to allocate integers from a
  24    pool without repetition */
  25
  26 /****************************************************************************
  27 allocate a bitmap of the specified size
  28 ****************************************************************************/
  29 struct bitmap *bitmap_allocate(int n)
  30 {
  31         struct bitmap *bm;
  32
  33         bm = (struct bitmap *)malloc(sizeof(*bm));
  34
  35         if (!bm) return NULL;
  36
  37         bm->n = n;
  38         bm->b = (uint32 *)malloc(sizeof(bm->b[0])*(n+31)/32);
  39         if (!bm->b) {
  40                 SAFE_FREE(bm);
  41                 return NULL;
  42         }
  43
  44         memset(bm->b, 0, sizeof(bm->b[0])*(n+31)/32);
  45
  46         return bm;
  47 }
  48
  49 /****************************************************************************
  50 free a bitmap.
  51 ****************************************************************************/
  52
  53 void bitmap_free(struct bitmap *bm)
  54 {
  55         if (!bm)
  56                 return;
  57
  58         SAFE_FREE(bm->b);
  59         SAFE_FREE(bm);
  60 }
  61
  62 /****************************************************************************
  63 set a bit in a bitmap
  64 ****************************************************************************/
  65 BOOL bitmap_set(struct bitmap *bm, unsigned i)
  66 {
  67         if (i >= bm->n) {
  68                 DEBUG(0,("Setting invalid bitmap entry %d (of %d)\n",
  69                       i, bm->n));
  70                 return False;
  71         }
  72         bm->b[i/32] |= (1<<(i%32));
  73         return True;
  74 }
  75
  76 /****************************************************************************
  77 clear a bit in a bitmap
  78 ****************************************************************************/
  79 BOOL bitmap_clear(struct bitmap *bm, unsigned i)
  80 {
  81         if (i >= bm->n) {
  82                 DEBUG(0,("clearing invalid bitmap entry %d (of %d)\n",
  83                       i, bm->n));
  84                 return False;
  85         }
  86         bm->b[i/32] &= ~(1<<(i%32));
  87         return True;
  88 }
  89
  90 /****************************************************************************
  91 query a bit in a bitmap
  92 ****************************************************************************/
  93 BOOL bitmap_query(struct bitmap *bm, unsigned i)
  94 {
  95         if (i >= bm->n) return False;
  96         if (bm->b[i/32] & (1<<(i%32))) {
  97                 return True;
  98         }
  99         return False;
 100 }
 101
 102 /****************************************************************************
 103 find a zero bit in a bitmap starting at the specified offset, with
 104 wraparound
 105 ****************************************************************************/
 106 int bitmap_find(struct bitmap *bm, unsigned ofs)
 107 {
 108         int i, j;
 109
 110         if (ofs > bm->n) ofs = 0;
 111
 112         i = ofs;
 113         while (i < bm->n) {
 114                 if (~(bm->b[i/32])) {
 115                         j = i;
 116                         do {
 117                                 if (!bitmap_query(bm, j)) return j;
 118                                 j++;
 119                         } while (j & 31 && j < bm->n);
 120                 }
 121                 i += 32;
 122                 i &= ~31;
 123         }
 124
 125         i = 0;
 126         while (i < ofs) {
 127                 if (~(bm->b[i/32])) {
 128                         j = i;
 129                         do {
 130                                 if (!bitmap_query(bm, j)) return j;
 131                                 j++;
 132                         } while (j & 31 && j < bm->n);
 133                 }
 134                 i += 32;
 135                 i &= ~31;
 136         }
 137
 138         return -1;
 139 }