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/*
* Copyright (C) 2004-2007, 2009 Internet Systems Consortium, Inc. ("ISC")
* Copyright (C) 2001, 2003 Internet Software Consortium.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
* REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
* OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
* PERFORMANCE OF THIS SOFTWARE.
*/
/* $Id: refcount.h,v 1.17 2009-09-29 23:48:04 tbox Exp $ */
#ifndef ISC_REFCOUNT_H
#define ISC_REFCOUNT_H 1
#include <isc/atomic.h>
#include <isc/lang.h>
#include <isc/mutex.h>
#include <isc/platform.h>
#include <isc/types.h>
#include <isc/util.h>
/*! \file isc/refcount.h
* \brief Implements a locked reference counter.
*
* These functions may actually be
* implemented using macros, and implementations of these macros are below.
* The isc_refcount_t type should not be accessed directly, as its contents
* depend on the implementation.
*/
ISC_LANG_BEGINDECLS
/*
* Function prototypes
*/
/*
* isc_result_t
* isc_refcount_init(isc_refcount_t *ref, unsigned int n);
*
* Initialize the reference counter. There will be 'n' initial references.
*
* Requires:
* ref != NULL
*/
/*
* void
* isc_refcount_destroy(isc_refcount_t *ref);
*
* Destroys a reference counter.
*
* Requires:
* ref != NULL
* The number of references is 0.
*/
/*
* void
* isc_refcount_increment(isc_refcount_t *ref, unsigned int *targetp);
* isc_refcount_increment0(isc_refcount_t *ref, unsigned int *targetp);
*
* Increments the reference count, returning the new value in targetp if it's
* not NULL. The reference counter typically begins with the initial counter
* of 1, and will be destroyed once the counter reaches 0. Thus,
* isc_refcount_increment() additionally requires the previous counter be
* larger than 0 so that an error which violates the usage can be easily
* caught. isc_refcount_increment0() does not have this restriction.
*
* Requires:
* ref != NULL.
*/
/*
* void
* isc_refcount_decrement(isc_refcount_t *ref, unsigned int *targetp);
*
* Decrements the reference count, returning the new value in targetp if it's
* not NULL.
*
* Requires:
* ref != NULL.
*/
/*
* Sample implementations
*/
#ifdef ISC_PLATFORM_USETHREADS
#ifdef ISC_PLATFORM_HAVEXADD
#define ISC_REFCOUNT_HAVEATOMIC 1
typedef struct isc_refcount {
isc_int32_t refs;
} isc_refcount_t;
#define isc_refcount_destroy(rp) REQUIRE((rp)->refs == 0)
#define isc_refcount_current(rp) ((unsigned int)((rp)->refs))
#define isc_refcount_increment0(rp, tp) \
do { \
unsigned int *_tmp = (unsigned int *)(tp); \
isc_int32_t prev; \
prev = isc_atomic_xadd(&(rp)->refs, 1); \
if (_tmp != NULL) \
*_tmp = prev + 1; \
} while (0)
#define isc_refcount_increment(rp, tp) \
do { \
unsigned int *_tmp = (unsigned int *)(tp); \
isc_int32_t prev; \
prev = isc_atomic_xadd(&(rp)->refs, 1); \
REQUIRE(prev > 0); \
if (_tmp != NULL) \
*_tmp = prev + 1; \
} while (0)
#define isc_refcount_decrement(rp, tp) \
do { \
unsigned int *_tmp = (unsigned int *)(tp); \
isc_int32_t prev; \
prev = isc_atomic_xadd(&(rp)->refs, -1); \
REQUIRE(prev > 0); \
if (_tmp != NULL) \
*_tmp = prev - 1; \
} while (0)
#else /* ISC_PLATFORM_HAVEXADD */
typedef struct isc_refcount {
int refs;
isc_mutex_t lock;
} isc_refcount_t;
/*% Destroys a reference counter. */
#define isc_refcount_destroy(rp) \
do { \
REQUIRE((rp)->refs == 0); \
DESTROYLOCK(&(rp)->lock); \
} while (0)
#define isc_refcount_current(rp) ((unsigned int)((rp)->refs))
/*% Increments the reference count, returning the new value in targetp if it's not NULL. */
#define isc_refcount_increment0(rp, tp) \
do { \
unsigned int *_tmp = (unsigned int *)(tp); \
LOCK(&(rp)->lock); \
++((rp)->refs); \
if (_tmp != NULL) \
*_tmp = ((rp)->refs); \
UNLOCK(&(rp)->lock); \
} while (0)
#define isc_refcount_increment(rp, tp) \
do { \
unsigned int *_tmp = (unsigned int *)(tp); \
LOCK(&(rp)->lock); \
REQUIRE((rp)->refs > 0); \
++((rp)->refs); \
if (_tmp != NULL) \
*_tmp = ((rp)->refs); \
UNLOCK(&(rp)->lock); \
} while (0)
/*% Decrements the reference count, returning the new value in targetp if it's not NULL. */
#define isc_refcount_decrement(rp, tp) \
do { \
unsigned int *_tmp = (unsigned int *)(tp); \
LOCK(&(rp)->lock); \
REQUIRE((rp)->refs > 0); \
--((rp)->refs); \
if (_tmp != NULL) \
*_tmp = ((rp)->refs); \
UNLOCK(&(rp)->lock); \
} while (0)
#endif /* ISC_PLATFORM_HAVEXADD */
#else /* ISC_PLATFORM_USETHREADS */
typedef struct isc_refcount {
int refs;
} isc_refcount_t;
#define isc_refcount_destroy(rp) REQUIRE((rp)->refs == 0)
#define isc_refcount_current(rp) ((unsigned int)((rp)->refs))
#define isc_refcount_increment0(rp, tp) \
do { \
unsigned int *_tmp = (unsigned int *)(tp); \
int _n = ++(rp)->refs; \
if (_tmp != NULL) \
*_tmp = _n; \
} while (0)
#define isc_refcount_increment(rp, tp) \
do { \
unsigned int *_tmp = (unsigned int *)(tp); \
int _n; \
REQUIRE((rp)->refs > 0); \
_n = ++(rp)->refs; \
if (_tmp != NULL) \
*_tmp = _n; \
} while (0)
#define isc_refcount_decrement(rp, tp) \
do { \
unsigned int *_tmp = (unsigned int *)(tp); \
int _n; \
REQUIRE((rp)->refs > 0); \
_n = --(rp)->refs; \
if (_tmp != NULL) \
*_tmp = _n; \
} while (0)
#endif /* ISC_PLATFORM_USETHREADS */
isc_result_t
isc_refcount_init(isc_refcount_t *ref, unsigned int n);
ISC_LANG_ENDDECLS
#endif /* ISC_REFCOUNT_H */