/* * 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