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