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Diffstat (limited to 'lib/isc/include/isc/refcount.h')
| -rw-r--r-- | lib/isc/include/isc/refcount.h | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/lib/isc/include/isc/refcount.h b/lib/isc/include/isc/refcount.h new file mode 100644 index 0000000..68e512c --- /dev/null +++ b/lib/isc/include/isc/refcount.h @@ -0,0 +1,156 @@ +/* + * Copyright (C) Internet Systems Consortium, Inc. ("ISC") + * + * SPDX-License-Identifier: MPL-2.0 + * + * 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 |