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/*
* QEMU Block backends
*
* Copyright (C) 2014 Red Hat, Inc.
*
* Authors:
* Markus Armbruster <armbru@redhat.com>,
*
* This work is licensed under the terms of the GNU LGPL, version 2.1
* or later. See the COPYING.LIB file in the top-level directory.
*/
#include "sysemu/block-backend.h"
#include "block/block_int.h"
struct BlockBackend {
char *name;
int refcnt;
QTAILQ_ENTRY(BlockBackend) link; /* for blk_backends */
};
/* All the BlockBackends */
static QTAILQ_HEAD(, BlockBackend) blk_backends =
QTAILQ_HEAD_INITIALIZER(blk_backends);
/*
* Create a new BlockBackend with @name, with a reference count of one.
* @name must not be null or empty.
* Fail if a BlockBackend with this name already exists.
* Store an error through @errp on failure, unless it's null.
* Return the new BlockBackend on success, null on failure.
*/
BlockBackend *blk_new(const char *name, Error **errp)
{
BlockBackend *blk;
assert(name && name[0]);
if (blk_by_name(name)) {
error_setg(errp, "Device with id '%s' already exists", name);
return NULL;
}
blk = g_new0(BlockBackend, 1);
blk->name = g_strdup(name);
blk->refcnt = 1;
QTAILQ_INSERT_TAIL(&blk_backends, blk, link);
return blk;
}
static void blk_delete(BlockBackend *blk)
{
assert(!blk->refcnt);
QTAILQ_REMOVE(&blk_backends, blk, link);
g_free(blk->name);
g_free(blk);
}
/*
* Increment @blk's reference count.
* @blk must not be null.
*/
void blk_ref(BlockBackend *blk)
{
blk->refcnt++;
}
/*
* Decrement @blk's reference count.
* If this drops it to zero, destroy @blk.
* For convenience, do nothing if @blk is null.
*/
void blk_unref(BlockBackend *blk)
{
if (blk) {
assert(blk->refcnt > 0);
if (!--blk->refcnt) {
blk_delete(blk);
}
}
}
/*
* Return the BlockBackend after @blk.
* If @blk is null, return the first one.
* Else, return @blk's next sibling, which may be null.
*
* To iterate over all BlockBackends, do
* for (blk = blk_next(NULL); blk; blk = blk_next(blk)) {
* ...
* }
*/
BlockBackend *blk_next(BlockBackend *blk)
{
return blk ? QTAILQ_NEXT(blk, link) : QTAILQ_FIRST(&blk_backends);
}
/*
* Return @blk's name, a non-null, non-empty string.
*/
const char *blk_name(BlockBackend *blk)
{
return blk->name;
}
/*
* Return the BlockBackend with name @name if it exists, else null.
* @name must not be null.
*/
BlockBackend *blk_by_name(const char *name)
{
BlockBackend *blk;
assert(name);
QTAILQ_FOREACH(blk, &blk_backends, link) {
if (!strcmp(name, blk->name)) {
return blk;
}
}
return NULL;
}
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