plugins/file/file.c

   1 /* nbdkit
   2  * Copyright (C) 2013 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 <string.h>
  39 #include <fcntl.h>
  40 #include <unistd.h>
  41 #include <sys/types.h>
  42 #include <sys/stat.h>
  43
  44 #include <nbdkit-plugin.h>
  45
  46 static char *filename = NULL;
  47
  48 static void
  49 file_unload (void)
  50 {
  51   free (filename);
  52 }
  53
  54 /* Called for each key=value passed on the command line.  This plugin
  55  * only accepts file=<filename>, which is required.
  56  */
  57 static int
  58 file_config (const char *key, const char *value)
  59 {
  60   if (strcmp (key, "file") == 0) {
  61     /* See FILENAMES AND PATHS in nbdkit-plugin(3). */
  62     filename = nbdkit_absolute_path (value);
  63     if (!filename)
  64       return -1;
  65   }
  66   else {
  67     nbdkit_error ("unknown parameter '%s'", key);
  68     return -1;
  69   }
  70
  71   return 0;
  72 }
  73
  74 /* Check the user did pass a file=<FILENAME> parameter. */
  75 static int
  76 file_config_complete (void)
  77 {
  78   if (filename == NULL) {
  79     nbdkit_error ("you must supply the file=<FILENAME> parameter after the plugin name on the command line");
  80     return -1;
  81   }
  82
  83   return 0;
  84 }
  85
  86 #define file_config_help \
  87   "file=<FILENAME>     (required) The filename to serve."
  88
  89 /* The per-connection handle. */
  90 struct handle {
  91   int fd;
  92 };
  93
  94 /* Create the per-connection handle. */
  95 static void *
  96 file_open (int readonly)
  97 {
  98   struct handle *h;
  99   int flags;
 100
 101   h = malloc (sizeof *h);
 102   if (h == NULL) {
 103     nbdkit_error ("malloc: %m");
 104     return NULL;
 105   }
 106
 107   flags = O_CLOEXEC|O_NOCTTY;
 108   if (readonly)
 109     flags |= O_RDONLY;
 110   else
 111     flags |= O_RDWR;
 112
 113   h->fd = open (filename, flags);
 114   if (h->fd == -1) {
 115     nbdkit_error ("open: %s: %m", filename);
 116     free (h);
 117     return NULL;
 118   }
 119
 120   return h;
 121 }
 122
 123 /* Free up the per-connection handle. */
 124 static void
 125 file_close (void *handle)
 126 {
 127   struct handle *h = handle;
 128
 129   close (h->fd);
 130   free (h);
 131 }
 132
 133 #define THREAD_MODEL NBDKIT_THREAD_MODEL_SERIALIZE_REQUESTS
 134
 135 /* Get the file size. */
 136 static int64_t
 137 file_get_size (void *handle)
 138 {
 139   struct handle *h = handle;
 140   struct stat statbuf;
 141
 142   if (fstat (h->fd, &statbuf) == -1) {
 143     nbdkit_error ("stat: %m");
 144     return -1;
 145   }
 146
 147   return statbuf.st_size;
 148 }
 149
 150 /* Read data from the file. */
 151 static int
 152 file_pread (void *handle, void *buf, uint32_t count, uint64_t offset)
 153 {
 154   struct handle *h = handle;
 155
 156   while (count > 0) {
 157     ssize_t r = pread (h->fd, buf, count, offset);
 158     if (r == -1) {
 159       nbdkit_error ("pread: %m");
 160       return -1;
 161     }
 162     if (r == 0) {
 163       nbdkit_error ("pread: unexpected end of file");
 164       return -1;
 165     }
 166     buf += r;
 167     count -= r;
 168     offset += r;
 169   }
 170
 171   return 0;
 172 }
 173
 174 /* Write data to the file. */
 175 static int
 176 file_pwrite (void *handle, const void *buf, uint32_t count, uint64_t offset)
 177 {
 178   struct handle *h = handle;
 179
 180   while (count > 0) {
 181     ssize_t r = pwrite (h->fd, buf, count, offset);
 182     if (r == -1) {
 183       nbdkit_error ("pwrite: %m");
 184       return -1;
 185     }
 186     buf += r;
 187     count -= r;
 188     offset += r;
 189   }
 190
 191   return 0;
 192 }
 193
 194 /* Flush the file to disk. */
 195 static int
 196 file_flush (void *handle)
 197 {
 198   struct handle *h = handle;
 199
 200   if (fdatasync (h->fd) == -1) {
 201     nbdkit_error ("fdatasync: %m");
 202     return -1;
 203   }
 204
 205   return 0;
 206 }
 207
 208 static struct nbdkit_plugin plugin = {
 209   .name              = "file",
 210   .longname          = "nbdkit file plugin",
 211   .version           = PACKAGE_VERSION,
 212   .unload            = file_unload,
 213   .config            = file_config,
 214   .config_complete   = file_config_complete,
 215   .config_help       = file_config_help,
 216   .open              = file_open,
 217   .close             = file_close,
 218   .get_size          = file_get_size,
 219   .pread             = file_pread,
 220   .pwrite            = file_pwrite,
 221   .flush             = file_flush,
 222 };
 223
 224 NBDKIT_REGISTER_PLUGIN(plugin)