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/** BEGIN COPYRIGHT BLOCK
* Copyright (C) 2001 Sun Microsystems, Inc. Used by permission.
* Copyright (C) 2005 Red Hat, Inc.
* All rights reserved.
*
* License: GPL (version 3 or any later version).
* See LICENSE for details.
* END COPYRIGHT BLOCK **/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
/* Implementation note:
PR_AtomicIncrement and PR_AtomicDecrement both return a value whose
sign is the same sign (or zero) as the variable *after* it was updated.
They do not return the previous value.
*/
#include "slapi-plugin.h"
#include "slapi-private.h"
typedef struct object
{
uint64_t refcnt; /* reference count for the object */
FNFree destructor; /* Destructor for the object */
void *data; /* pointer to actual node data */
} object;
/*
* Create a new object.
* The object is created with refcnt set to 1. The caller implicitly gets
* a reference to the object, to prevent a race condition where the object
* is destroyed immediately after contruction.
* The provided destructor function will be called when all references to
* the object have been released.
*
* Returns a pointer to the new object.
*/
Object *
object_new(void *user_data, FNFree destructor)
{
Object *o;
o = (object *)slapi_ch_malloc(sizeof(object));
o->destructor = destructor;
o->data = user_data;
slapi_atomic_store_64(&(o->refcnt), 1, __ATOMIC_RELEASE);
return o;
}
/*
* Acquire a reference object. The caller must hold a reference
* to the object, or know for certain that a reference is held
* and will continue to be held while this call is in progress.
*/
void
object_acquire(Object *o)
{
PR_ASSERT(NULL != o);
slapi_atomic_incr_64(&(o->refcnt), __ATOMIC_RELEASE);
}
/*
* Release a reference to an object. The pointer to the object
* should not be referenced after this call is made, since the
* object may be destroyed if this is the last reference to it.
*/
void
object_release(Object *o)
{
PRInt32 refcnt_after_release;
PR_ASSERT(NULL != o);
refcnt_after_release = slapi_atomic_decr_64(&(o->refcnt), __ATOMIC_ACQ_REL);
if (refcnt_after_release == 0) {
/* Object can be destroyed */
if (o->destructor)
o->destructor(&o->data);
/* Make it harder to reuse a dangling pointer */
o->data = NULL;
o->destructor = NULL;
slapi_ch_free((void **)&o);
}
}
/*
* Get the data pointer from an object.
* Results are undefined if the caller does not hold a reference
* to the object.
*/
void *
object_get_data(Object *o)
{
PR_ASSERT(NULL != o);
return o->data;
}
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