/* nbdkit * Copyright (C) 2013 Red Hat Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are * met: * * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * * Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * * Neither the name of Red Hat nor the names of its contributors may be * used to endorse or promote products derived from this software without * specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ /* example2: * * A simple but more realistic read-only file server. */ #include <config.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <fcntl.h> #include <unistd.h> #include <sys/types.h> #include <sys/stat.h> #include <nbdkit-plugin.h> static char *filename = NULL; static void example2_unload (void) { free (filename); } /* Called for each key=value passed on the command line. This plugin * only accepts file=<filename>, which is required. */ static int example2_config (const char *key, const char *value) { if (strcmp (key, "file") == 0) { /* See FILENAMES AND PATHS in nbdkit-plugin(3). */ filename = nbdkit_absolute_path (value); if (!filename) return -1; } else { nbdkit_error ("unknown parameter '%s'", key); return -1; } return 0; } /* Check the user did pass a file=<FILENAME> parameter. */ static int example2_config_complete (void) { if (filename == NULL) { nbdkit_error ("you must supply the file=<FILENAME> parameter after the plugin name on the command line"); return -1; } return 0; } #define example2_config_help \ "file=<FILENAME> (required) The filename to serve." /* The per-connection handle. */ struct example2_handle { int fd; }; /* Create the per-connection handle. * * Because this plugin can only serve readonly, we can ignore the * 'readonly' parameter. */ static void * example2_open (int readonly) { struct example2_handle *h; h = malloc (sizeof *h); if (h == NULL) { nbdkit_error ("malloc: %m"); return NULL; } h->fd = open (filename, O_RDONLY|O_CLOEXEC); if (h->fd == -1) { nbdkit_error ("open: %s: %m", filename); free (h); return NULL; } return h; } /* Free up the per-connection handle. */ static void example2_close (void *handle) { struct example2_handle *h = handle; close (h->fd); free (h); } /* In fact NBDKIT_THREAD_MODEL_SERIALIZE_REQUESTS would work here. * However for the benefit of people who blindly cut and paste code * without bothering to read any documentation, leave this at a safe * default. */ #define THREAD_MODEL NBDKIT_THREAD_MODEL_SERIALIZE_ALL_REQUESTS /* Get the file size. */ static int64_t example2_get_size (void *handle) { struct example2_handle *h = handle; struct stat statbuf; if (fstat (h->fd, &statbuf) == -1) { nbdkit_error ("stat: %m"); return -1; } return statbuf.st_size; } /* Read data from the file. */ static int example2_pread (void *handle, void *buf, uint32_t count, uint64_t offset) { struct example2_handle *h = handle; while (count > 0) { ssize_t r = pread (h->fd, buf, count, offset); if (r == -1) { nbdkit_error ("pread: %m"); return -1; } if (r == 0) { nbdkit_error ("pread: unexpected end of file"); return -1; } buf += r; count -= r; offset += r; } return 0; } static struct nbdkit_plugin plugin = { .name = "example2", .version = PACKAGE_VERSION, .unload = example2_unload, .config = example2_config, .config_complete = example2_config_complete, .config_help = example2_config_help, .open = example2_open, .close = example2_close, .get_size = example2_get_size, .pread = example2_pread, }; NBDKIT_REGISTER_PLUGIN(plugin)