plugins/example2/winexample2.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 /* example2:
  34  *
  35  * A simple but more realistic read-only file server.
  36  */
  37
  38 #ifndef WIN32
  39 #error "build error: winexample2.c should only be used on Windows"
  40 #endif
  41
  42 #include <config.h>
  43
  44 #include <stdio.h>
  45 #include <stdlib.h>
  46 #include <stdint.h>
  47 #include <string.h>
  48 #include <fcntl.h>
  49 #include <sys/types.h>
  50
  51 #include <ws2tcpip.h>
  52 #include <windows.h>
  53
  54 #define NBDKIT_API_VERSION 2
  55 #include <nbdkit-plugin.h>
  56
  57 static char *filename = NULL;
  58
  59 /* A debug flag which can be set on the command line using
  60  * '-D example2.extra=1' to enable very verbose debugging to help
  61  * developers.  Use the debug flags for extra debugging which would
  62  * only be useful for the original developers of the plugin.  For
  63  * ordinary debugging, just use nbdkit_debug and enable messages with
  64  * the -v flag on the command line.
  65  */
  66 NBDKIT_DLL_PUBLIC int example2_debug_extra = 0;
  67
  68 static void
  69 example2_unload (void)
  70 {
  71   free (filename);
  72 }
  73
  74 /* If you want to display extra information about the plugin when
  75  * the user does ‘nbdkit example2 --dump-plugin’ then you can print
  76  * ‘key=value’ lines here.
  77  */
  78 static void
  79 example2_dump_plugin (void)
  80 {
  81   printf ("example2_extra=hello\n");
  82 }
  83
  84 /* Called for each key=value passed on the command line.  This plugin
  85  * only accepts file=<filename>, which is required.
  86  */
  87 static int
  88 example2_config (const char *key, const char *value)
  89 {
  90   if (strcmp (key, "file") == 0) {
  91     /* See FILENAMES AND PATHS in nbdkit-plugin(3). */
  92     filename = nbdkit_realpath (value);
  93     if (!filename)
  94       return -1;
  95   }
  96   else {
  97     nbdkit_error ("unknown parameter '%s'", key);
  98     return -1;
  99   }
 100
 101   return 0;
 102 }
 103
 104 /* Check the user did pass a file=<FILENAME> parameter. */
 105 static int
 106 example2_config_complete (void)
 107 {
 108   if (filename == NULL) {
 109     nbdkit_error ("you must supply the file=<FILENAME> parameter "
 110                   "after the plugin name on the command line");
 111     return -1;
 112   }
 113
 114   return 0;
 115 }
 116
 117 #define example2_config_help \
 118   "file=<FILENAME>     (required) The filename to serve."
 119
 120 /* The per-connection handle. */
 121 struct example2_handle {
 122   HANDLE fh;
 123 };
 124
 125 /* Create the per-connection handle.
 126  *
 127  * Because this plugin can only serve readonly, we can ignore the
 128  * 'readonly' parameter.
 129  */
 130 static void *
 131 example2_open (int readonly)
 132 {
 133   struct example2_handle *h;
 134
 135   h = malloc (sizeof *h);
 136   if (h == NULL) {
 137     nbdkit_error ("malloc: error %lu", GetLastError ());
 138     return NULL;
 139   }
 140
 141   h->fh = CreateFile (filename, GENERIC_READ, FILE_SHARE_READ|FILE_SHARE_WRITE,
 142                       NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
 143   if (h->fh == INVALID_HANDLE_VALUE) {
 144     nbdkit_error ("CreateFile: %s: error %lu", filename, GetLastError ());
 145     free (h);
 146     return NULL;
 147   }
 148
 149   return h;
 150 }
 151
 152 /* Free up the per-connection handle. */
 153 static void
 154 example2_close (void *handle)
 155 {
 156   struct example2_handle *h = handle;
 157
 158   CloseHandle (h->fh);
 159   free (h);
 160 }
 161
 162 /* In fact NBDKIT_THREAD_MODEL_SERIALIZE_REQUESTS would work here.
 163  * However for the benefit of people who blindly cut and paste code
 164  * without bothering to read any documentation, leave this at a safe
 165  * default.
 166  */
 167 #define THREAD_MODEL NBDKIT_THREAD_MODEL_SERIALIZE_ALL_REQUESTS
 168
 169 /* Get the file size. */
 170 static int64_t
 171 example2_get_size (void *handle)
 172 {
 173   struct example2_handle *h = handle;
 174   LARGE_INTEGER size = { 0 };
 175
 176   if (!GetFileSizeEx (h->fh, &size)) {
 177     nbdkit_error ("%s: GetFileSizeEx: error %lu", filename, GetLastError ());
 178     return -1;
 179   }
 180
 181   /* Use the debug flags for extra debugging which would only be
 182    * useful for the original developers of the plugin.  For ordinary
 183    * debugging, just use nbdkit_debug and enable messages with the -v
 184    * flag on the command line.  This is a contrived example of how to
 185    * use debug flags.
 186    */
 187   if (example2_debug_extra)
 188     nbdkit_debug ("extra debugging: size = %I64d", (long long)size.QuadPart);
 189
 190   return size.QuadPart;
 191 }
 192
 193 /* Read data from the file. */
 194 static int
 195 example2_pread (void *handle, void *buf, uint32_t count, uint64_t offset,
 196                 uint32_t flags)
 197 {
 198   struct example2_handle *h = handle;
 199   DWORD r;
 200   OVERLAPPED ovl;
 201
 202   memset (&ovl, 0, sizeof ovl);
 203   ovl.Offset = offset & 0xffffffff;
 204   ovl.OffsetHigh = offset >> 32;
 205
 206   /* XXX Will fail weirdly if count is larger than 32 bits. */
 207   if (!ReadFile (h->fh, buf, count, &r, &ovl)) {
 208     nbdkit_error ("%s: ReadFile: error %lu", filename, GetLastError ());
 209     return -1;
 210   }
 211
 212   return 0;
 213 }
 214
 215 static struct nbdkit_plugin plugin = {
 216   .name              = "example2",
 217   .version           = PACKAGE_VERSION,
 218   .unload            = example2_unload,
 219   .dump_plugin       = example2_dump_plugin,
 220   .config            = example2_config,
 221   .config_complete   = example2_config_complete,
 222   .config_help       = example2_config_help,
 223   .open              = example2_open,
 224   .close             = example2_close,
 225   .get_size          = example2_get_size,
 226   .pread             = example2_pread,
 227 };
 228
 229 NBDKIT_REGISTER_PLUGIN (plugin)