/*
* Copyright (C) Internet Systems Consortium, Inc. ("ISC")
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, you can obtain one at https://mozilla.org/MPL/2.0/.
*
* See the COPYRIGHT file distributed with this work for additional
* information regarding copyright ownership.
*/
#pragma once
#include <inttypes.h>
#include <isc/assertions.h>
#include <isc/atomic.h>
#include <isc/error.h>
#include <isc/lang.h>
#include <isc/mutex.h>
#include <isc/platform.h>
#include <isc/types.h>
/*! \file isc/refcount.h
* \brief Implements a locked reference counter.
*
* These macros uses C11(-like) atomic functions to implement reference
* counting. The isc_refcount_t type must not be accessed directly.
*/
ISC_LANG_BEGINDECLS
typedef atomic_uint_fast32_t isc_refcount_t;
/** \def isc_refcount_init(ref, n)
* \brief Initialize the reference counter.
* \param[in] ref pointer to reference counter.
* \param[in] n an initial number of references.
* \return nothing.
*
* \warning No memory barrier are being imposed here.
*/
#define isc_refcount_init(target, value) atomic_init(target, value)
/** \def isc_refcount_current(ref)
* \brief Returns current number of references.
* \param[in] ref pointer to reference counter.
* \returns current value of reference counter.
*
* Undo implicit promotion to 64 bits in our Windows implementation of
* atomic_load_explicit() by casting to uint_fast32_t.
*/
#define isc_refcount_current(target) (uint_fast32_t) atomic_load_acquire(target)
/** \def isc_refcount_destroy(ref)
* \brief a destructor that makes sure that all references were cleared.
* \param[in] ref pointer to reference counter.
* \returns nothing.
*/
#define isc_refcount_destroy(target) \
ISC_REQUIRE(isc_refcount_current(target) == 0)
/** \def isc_refcount_increment0(ref)
* \brief increases reference counter by 1.
* \param[in] ref pointer to reference counter.
* \returns previous value of reference counter.
*/
#if _MSC_VER
static inline uint_fast32_t
isc_refcount_increment0(isc_refcount_t *target) {
uint_fast32_t __v;
__v = (uint_fast32_t)atomic_fetch_add_relaxed(target, 1);
INSIST(__v < UINT32_MAX);
return (__v);
}
#else /* _MSC_VER */
#define isc_refcount_increment0(target) \
({ \
/* cppcheck-suppress shadowVariable */ \
uint_fast32_t __v; \
__v = atomic_fetch_add_relaxed(target, 1); \
INSIST(__v < UINT32_MAX); \
__v; \
})
#endif /* _MSC_VER */
/** \def isc_refcount_increment(ref)
* \brief increases reference counter by 1.
* \param[in] ref pointer to reference counter.
* \returns previous value of reference counter.
*/
#if _MSC_VER
static inline uint_fast32_t
isc_refcount_increment(isc_refcount_t *target) {
uint_fast32_t __v;
__v = (uint_fast32_t)atomic_fetch_add_relaxed(target, 1);
INSIST(__v > 0 && __v < UINT32_MAX);
return (__v);
}
#else /* _MSC_VER */
#define isc_refcount_increment(target) \
({ \
/* cppcheck-suppress shadowVariable */ \
uint_fast32_t __v; \
__v = atomic_fetch_add_relaxed(target, 1); \
INSIST(__v > 0 && __v < UINT32_MAX); \
__v; \
})
#endif /* _MSC_VER */
/** \def isc_refcount_decrement(ref)
* \brief decreases reference counter by 1.
* \param[in] ref pointer to reference counter.
* \returns previous value of reference counter.
*/
#if _MSC_VER
static inline uint_fast32_t
isc_refcount_decrement(isc_refcount_t *target) {
uint_fast32_t __v;
__v = (uint_fast32_t)atomic_fetch_sub_acq_rel(target, 1);
INSIST(__v > 0);
return (__v);
}
#else /* _MSC_VER */
#define isc_refcount_decrement(target) \
({ \
/* cppcheck-suppress shadowVariable */ \
uint_fast32_t __v; \
__v = atomic_fetch_sub_acq_rel(target, 1); \
INSIST(__v > 0); \
__v; \
})
#endif /* _MSC_VER */
#define isc_refcount_decrementz(target) \
do { \
uint_fast32_t _refs = isc_refcount_decrement(target); \
ISC_INSIST(_refs == 1); \
} while (0)
#define isc_refcount_decrement1(target) \
do { \
uint_fast32_t _refs = isc_refcount_decrement(target); \
ISC_INSIST(_refs > 1); \
} while (0)
#define isc_refcount_decrement0(target) \
do { \
uint_fast32_t _refs = isc_refcount_decrement(target); \
ISC_INSIST(_refs > 0); \
} while (0)
ISC_LANG_ENDDECLS
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