plugins/pattern/pattern.c

   1 /* nbdkit
   2  * Copyright (C) 2017-2020 Red Hat Inc.
   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 #include <errno.h>
  41 #include <time.h>
  42
  43 #define NBDKIT_API_VERSION 2
  44 #include <nbdkit-plugin.h>
  45
  46 #include "byte-swapping.h"
  47 #include "minmax.h"
  48
  49 /* The size of disk in bytes (initialized by size=<SIZE> parameter). */
  50 static int64_t size = 0;
  51
  52 static int
  53 pattern_config (const char *key, const char *value)
  54 {
  55   int64_t r;
  56
  57   if (strcmp (key, "size") == 0) {
  58     r = nbdkit_parse_size (value);
  59     if (r == -1)
  60       return -1;
  61     size = r;
  62   }
  63   else {
  64     nbdkit_error ("unknown parameter '%s'", key);
  65     return -1;
  66   }
  67
  68   return 0;
  69 }
  70
  71 #define pattern_config_help \
  72   "size=<SIZE>  (required) Size of the backing disk"
  73
  74 #define THREAD_MODEL NBDKIT_THREAD_MODEL_PARALLEL
  75
  76 /* Create the per-connection handle. */
  77 static void *
  78 pattern_open (int readonly)
  79 {
  80   return NBDKIT_HANDLE_NOT_NEEDED;
  81 }
  82
  83 /* Get the disk size. */
  84 static int64_t
  85 pattern_get_size (void *handle)
  86 {
  87   return size;
  88 }
  89
  90 /* Serves the same data over multiple connections. */
  91 static int
  92 pattern_can_multi_conn (void *handle)
  93 {
  94   return 1;
  95 }
  96
  97 /* Cache. */
  98 static int
  99 pattern_can_cache (void *handle)
 100 {
 101   /* Everything is already in memory, returning this without
 102    * implementing .cache lets nbdkit do the correct no-op.
 103    */
 104   return NBDKIT_CACHE_NATIVE;
 105 }
 106
 107 /* Read data. */
 108 static int
 109 pattern_pread (void *handle, void *buf, uint32_t count, uint64_t offset,
 110                uint32_t flags)
 111 {
 112   char *b = buf;
 113   uint64_t d;
 114   uint64_t o;
 115   uint32_t n;
 116
 117   while (count > 0) {
 118     d = htobe64 (offset & ~7);
 119     o = offset & 7;
 120     n = MIN (count, 8-o);
 121     memcpy (b, (char *)&d + o, n);
 122     b += 8-o;
 123     offset += 8-o;
 124     count -= n;
 125   }
 126
 127   return 0;
 128 }
 129
 130 static struct nbdkit_plugin plugin = {
 131   .name              = "pattern",
 132   .version           = PACKAGE_VERSION,
 133   .config            = pattern_config,
 134   .config_help       = pattern_config_help,
 135   .magic_config_key  = "size",
 136   .open              = pattern_open,
 137   .get_size          = pattern_get_size,
 138   .can_multi_conn    = pattern_can_multi_conn,
 139   .can_cache         = pattern_can_cache,
 140   .pread             = pattern_pread,
 141   /* In this plugin, errno is preserved properly along error return
 142    * paths from failed system calls.
 143    */
 144   .errno_is_preserved = 1,
 145 };
 146
 147 NBDKIT_REGISTER_PLUGIN (plugin)