filters/offset/offset.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 <stdint.h>
  38 #include <inttypes.h>
  39 #include <string.h>
  40
  41 #include <nbdkit-filter.h>
  42
  43 #include "cleanup.h"
  44
  45 static int64_t offset = 0, range = -1;
  46
  47 /* Called for each key=value passed on the command line. */
  48 static int
  49 offset_config (nbdkit_next_config *next, nbdkit_backend *nxdata,
  50                const char *key, const char *value)
  51 {
  52   if (strcmp (key, "offset") == 0) {
  53     offset = nbdkit_parse_size (value);
  54     if (offset == -1)
  55       return -1;
  56     return 0;
  57   }
  58   else if (strcmp (key, "range") == 0) {
  59     range = nbdkit_parse_size (value);
  60     if (range == -1)
  61       return -1;
  62     return 0;
  63   }
  64   else
  65     return next (nxdata, key, value);
  66 }
  67
  68 #define offset_config_help \
  69   "offset=<OFFSET>            The start offset to serve (default 0).\n" \
  70   "range=<LENGTH>             The total size to serve (default rest of file)."
  71
  72 /* Get the file size. */
  73 static int64_t
  74 offset_get_size (nbdkit_next *next,
  75                  void *handle)
  76 {
  77   int64_t real_size = next->get_size (next);
  78
  79   if (real_size == -1)
  80     return -1;
  81
  82   if (range >= 0) {
  83     if (offset > real_size - range) {
  84       nbdkit_error ("offset+range (%" PRIi64 "+%" PRIi64 ") "
  85                     "is larger than the real size (%" PRIi64 ") "
  86                     "of the underlying file or device",
  87                     offset, range, real_size);
  88       return -1;
  89     }
  90     return range;
  91   }
  92   else if (offset > real_size) {
  93     nbdkit_error ("offset (%" PRIi64 ") "
  94                   "is larger than the real size (%" PRIi64 ") "
  95                   "of the underlying file or device",
  96                   offset, real_size);
  97     return -1;
  98   }
  99   else
 100     return real_size - offset;
 101 }
 102
 103 /* Read data. */
 104 static int
 105 offset_pread (nbdkit_next *next,
 106               void *handle, void *buf, uint32_t count, uint64_t offs,
 107               uint32_t flags, int *err)
 108 {
 109   return next->pread (next, buf, count, offs + offset, flags, err);
 110 }
 111
 112 /* Write data. */
 113 static int
 114 offset_pwrite (nbdkit_next *next,
 115                void *handle,
 116                const void *buf, uint32_t count, uint64_t offs, uint32_t flags,
 117                int *err)
 118 {
 119   return next->pwrite (next, buf, count, offs + offset, flags, err);
 120 }
 121
 122 /* Trim data. */
 123 static int
 124 offset_trim (nbdkit_next *next,
 125              void *handle, uint32_t count, uint64_t offs, uint32_t flags,
 126              int *err)
 127 {
 128   return next->trim (next, count, offs + offset, flags, err);
 129 }
 130
 131 /* Zero data. */
 132 static int
 133 offset_zero (nbdkit_next *next,
 134              void *handle, uint32_t count, uint64_t offs, uint32_t flags,
 135              int *err)
 136 {
 137   return next->zero (next, count, offs + offset, flags, err);
 138 }
 139
 140 /* Extents. */
 141 static int
 142 offset_extents (nbdkit_next *next,
 143                 void *handle, uint32_t count, uint64_t offs, uint32_t flags,
 144                 struct nbdkit_extents *extents, int *err)
 145 {
 146   size_t i;
 147   CLEANUP_EXTENTS_FREE struct nbdkit_extents *extents2 = NULL;
 148   struct nbdkit_extent e;
 149   int64_t end = range >= 0 ? offset + range : next->get_size (next);
 150
 151   extents2 = nbdkit_extents_new (offs + offset, end);
 152   if (extents2 == NULL) {
 153     *err = errno;
 154     return -1;
 155   }
 156   if (next->extents (next, count, offs + offset, flags, extents2, err) == -1)
 157     return -1;
 158
 159   for (i = 0; i < nbdkit_extents_count (extents2); ++i) {
 160     e = nbdkit_get_extent (extents2, i);
 161     e.offset -= offset;
 162     if (nbdkit_add_extent (extents, e.offset, e.length, e.type) == -1) {
 163       *err = errno;
 164       return -1;
 165     }
 166   }
 167   return 0;
 168 }
 169
 170 /* Cache data. */
 171 static int
 172 offset_cache (nbdkit_next *next,
 173               void *handle, uint32_t count, uint64_t offs, uint32_t flags,
 174               int *err)
 175 {
 176   return next->cache (next, count, offs + offset, flags, err);
 177 }
 178
 179 static struct nbdkit_filter filter = {
 180   .name              = "offset",
 181   .longname          = "nbdkit offset filter",
 182   .config            = offset_config,
 183   .config_help       = offset_config_help,
 184   .get_size          = offset_get_size,
 185   .pread             = offset_pread,
 186   .pwrite            = offset_pwrite,
 187   .trim              = offset_trim,
 188   .zero              = offset_zero,
 189   .extents           = offset_extents,
 190   .cache             = offset_cache,
 191 };
 192
 193 NBDKIT_REGISTER_FILTER (filter)