common/bitmap/bitmap.c

   1 /* nbdkit
   2  * Copyright Red Hat
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *
  11  * * Redistributions in binary form must reproduce the above copyright
  12  * notice, this list of conditions and the following disclaimer in the
  13  * documentation and/or other materials provided with the distribution.
  14  *
  15  * * Neither the name of Red Hat nor the names of its contributors may be
  16  * used to endorse or promote products derived from this software without
  17  * specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  22  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  26  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  27  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  29  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <config.h>
  34
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <string.h>
  38 #include <stdint.h>
  39
  40 #include <nbdkit-plugin.h>
  41
  42 #include "bitmap.h"
  43 #include "rounding.h"
  44 #include "nextnonzero.h"
  45
  46 int
  47 bitmap_resize (struct bitmap *bm, uint64_t new_size)
  48 {
  49   uint8_t *new_bitmap;
  50   const size_t old_bm_size = bm->size;
  51   uint64_t new_bm_size_u64;
  52   size_t new_bm_size;
  53
  54   new_bm_size_u64 = DIV_ROUND_UP (new_size,
  55                                   bm->blksize * UINT64_C (8) / bm->bpb);
  56   if (new_bm_size_u64 > SIZE_MAX) {
  57     nbdkit_error ("bitmap too large for this architecture");
  58     return -1;
  59   }
  60   new_bm_size = (size_t) new_bm_size_u64;
  61
  62   if (new_bm_size > 0) {
  63     new_bitmap = realloc (bm->bitmap, new_bm_size);
  64     if (new_bitmap == NULL) {
  65       nbdkit_error ("realloc: %m");
  66       return -1;
  67     }
  68   }
  69   else {
  70     free (bm->bitmap);
  71     new_bitmap = NULL;
  72   }
  73   bm->bitmap = new_bitmap;
  74   bm->size = new_bm_size;
  75   if (old_bm_size < new_bm_size)
  76     memset (&bm->bitmap[old_bm_size], 0, new_bm_size-old_bm_size);
  77
  78   nbdkit_debug ("bitmap resized to %zu bytes", new_bm_size);
  79
  80   return 0;
  81 }
  82
  83 int64_t
  84 bitmap_next (const struct bitmap *bm, uint64_t blk)
  85 {
  86   uint64_t limit = bm->size * bm->ibpb;
  87   const uint8_t *p;
  88
  89   /* Align to the next byte boundary. */
  90   for (; blk < limit && (blk & (bm->ibpb-1)) != 0; ++blk) {
  91     if (bitmap_get_blk (bm, blk, 0) != 0)
  92       return blk;
  93   }
  94   if (blk == limit)
  95     return -1;
  96
  97   /* Now we're at a byte boundary we can use a fast string function to
  98    * find the next non-zero byte.
  99    */
 100   p = &bm->bitmap[blk >> (3 - bm->bitshift)];
 101   p = (const uint8_t *) next_non_zero ((const char *) p,
 102                                        &bm->bitmap[bm->size] - p);
 103   if (p == NULL)
 104     return -1;
 105
 106   /* Now check the non-zero byte to find out which bit (ie. block) is set. */
 107   blk = (p - bm->bitmap) << (3 - bm->bitshift);
 108   for (; blk < limit; ++blk) {
 109     if (bitmap_get_blk (bm, blk, 0) != 0)
 110       return blk;
 111   }
 112
 113   /* Should never be reached. */
 114   abort ();
 115 }