filters/offset/offset.c

   1 /* nbdkit
   2  * Copyright (C) 2018 Red Hat Inc.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met:
   8  *
   9  * * Redistributions of source code must retain the above copyright
  10  * notice, this list of conditions and the following disclaimer.
  11  *
  12  * * Redistributions in binary form must reproduce the above copyright
  13  * notice, this list of conditions and the following disclaimer in the
  14  * documentation and/or other materials provided with the distribution.
  15  *
  16  * * Neither the name of Red Hat nor the names of its contributors may be
  17  * used to endorse or promote products derived from this software without
  18  * specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  22  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  23  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
  24  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  25  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  26  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  27  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  28  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  30  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #include <config.h>
  35
  36 #include <stdio.h>
  37 #include <stdlib.h>
  38 #include <stdint.h>
  39 #include <string.h>
  40
  41 #include <nbdkit-filter.h>
  42
  43 #define THREAD_MODEL NBDKIT_THREAD_MODEL_PARALLEL
  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, void *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 /* Check the user did pass both parameters. */
  69 static int
  70 offset_config_complete (nbdkit_next_config_complete *next, void *nxdata)
  71 {
  72   return next (nxdata);
  73 }
  74
  75 #define offset_config_help \
  76   "offset=<OFFSET>     (required) The start offset to serve.\n" \
  77   "range=<LENGTH>                 The total size to serve."
  78
  79 /* Get the file size. */
  80 static int64_t
  81 offset_get_size (struct nbdkit_next_ops *next_ops, void *nxdata,
  82                  void *handle)
  83 {
  84   int64_t real_size = next_ops->get_size (nxdata);
  85
  86   if (range >= 0) {
  87     if (offset + range > real_size) {
  88       nbdkit_error ("offset+range is larger than the real size of the underlying file or device");
  89       return -1;
  90     }
  91     return range;
  92   }
  93   else
  94     return real_size - offset;
  95 }
  96
  97 /* Read data. */
  98 static int
  99 offset_pread (struct nbdkit_next_ops *next_ops, void *nxdata,
 100               void *handle, void *buf, uint32_t count, uint64_t offs,
 101               uint32_t flags, int *err)
 102 {
 103   return next_ops->pread (nxdata, buf, count, offs + offset, flags, err);
 104 }
 105
 106 /* Write data. */
 107 static int
 108 offset_pwrite (struct nbdkit_next_ops *next_ops, void *nxdata,
 109                void *handle,
 110                const void *buf, uint32_t count, uint64_t offs, uint32_t flags,
 111                int *err)
 112 {
 113   return next_ops->pwrite (nxdata, buf, count, offs + offset, flags, err);
 114 }
 115
 116 /* Trim data. */
 117 static int
 118 offset_trim (struct nbdkit_next_ops *next_ops, void *nxdata,
 119              void *handle, uint32_t count, uint64_t offs, uint32_t flags,
 120              int *err)
 121 {
 122   return next_ops->trim (nxdata, count, offs + offset, flags, err);
 123 }
 124
 125 /* Zero data. */
 126 static int
 127 offset_zero (struct nbdkit_next_ops *next_ops, void *nxdata,
 128              void *handle, uint32_t count, uint64_t offs, uint32_t flags,
 129              int *err)
 130 {
 131   return next_ops->zero (nxdata, count, offs + offset, flags, err);
 132 }
 133
 134 static struct nbdkit_filter filter = {
 135   .name              = "offset",
 136   .longname          = "nbdkit offset filter",
 137   .version           = PACKAGE_VERSION,
 138   .config            = offset_config,
 139   .config_complete   = offset_config_complete,
 140   .config_help       = offset_config_help,
 141   .get_size          = offset_get_size,
 142   .pread             = offset_pread,
 143   .pwrite            = offset_pwrite,
 144   .trim              = offset_trim,
 145   .zero              = offset_zero,
 146 };
 147
 148 NBDKIT_REGISTER_FILTER(filter)