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/* nbdkit
* Copyright Red Hat
*
* 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.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <errno.h>
#define NBDKIT_API_VERSION 2
#include <nbdkit-plugin.h>
/* The size of disk in bytes (initialized by size=<SIZE> parameter). */
static int64_t size = 0;
static int
null_config (const char *key, const char *value)
{
int64_t r;
if (strcmp (key, "size") == 0) {
r = nbdkit_parse_size (value);
if (r == -1)
return -1;
size = r;
}
else {
nbdkit_error ("unknown parameter '%s'", key);
return -1;
}
return 0;
}
#define null_config_help \
"size=<SIZE> Size of the backing disk"
/* Create the per-connection handle. */
static void *
null_open (int readonly)
{
return NBDKIT_HANDLE_NOT_NEEDED;
}
#define THREAD_MODEL NBDKIT_THREAD_MODEL_PARALLEL
/* Get the disk size. */
static int64_t
null_get_size (void *handle)
{
return size;
}
/* Serves the same data over multiple connections. */
static int
null_can_multi_conn (void *handle)
{
return 1;
}
/* Cache. */
static int
null_can_cache (void *handle)
{
/* Everything is already in memory, returning this without
* implementing .cache lets nbdkit do the correct no-op.
*/
return NBDKIT_CACHE_NATIVE;
}
/* Fast zero. */
static int
null_can_fast_zero (void *handle)
{
return 1;
}
/* Read data. */
static int
null_pread (void *handle, void *buf, uint32_t count, uint64_t offset,
uint32_t flags)
{
memset (buf, 0, count);
return 0;
}
/* Write data. */
static int
null_pwrite (void *handle, const void *buf, uint32_t count, uint64_t offset,
uint32_t flags)
{
/* nothing */
return 0;
}
/* Write zeroes. */
static int
null_zero (void *handle, uint32_t count, uint64_t offset, uint32_t flags)
{
/* nothing */
return 0;
}
/* Flush is a no-op, so advertise native FUA support */
static int
null_can_fua (void *handle)
{
return NBDKIT_FUA_NATIVE;
}
/* Trim. */
static int
null_trim (void *handle, uint32_t count, uint64_t offset, uint32_t flags)
{
/* nothing */
return 0;
}
/* Nothing is persistent, so flush is trivially supported */
static int
null_flush (void *handle, uint32_t flags)
{
return 0;
}
/* Extents. */
static int
null_extents (void *handle, uint32_t count, uint64_t offset, uint32_t flags,
struct nbdkit_extents *extents)
{
return nbdkit_add_extent (extents, 0, size,
NBDKIT_EXTENT_HOLE | NBDKIT_EXTENT_ZERO);
}
static struct nbdkit_plugin plugin = {
.name = "null",
.version = PACKAGE_VERSION,
.config = null_config,
.config_help = null_config_help,
.magic_config_key = "size",
.open = null_open,
.get_size = null_get_size,
.can_multi_conn = null_can_multi_conn,
.can_cache = null_can_cache,
.can_fast_zero = null_can_fast_zero,
.pread = null_pread,
.pwrite = null_pwrite,
.zero = null_zero,
.trim = null_trim,
.can_fua = null_can_fua,
.flush = null_flush,
.extents = null_extents,
/* In this plugin, errno is preserved properly along error return
* paths from failed system calls.
*/
.errno_is_preserved = 1,
};
NBDKIT_REGISTER_PLUGIN (plugin)
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