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+/*
+ * 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/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) \
+ ({ \
+ 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) \
+ ({ \
+ 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) \
+ ({ \
+ 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)
+
+#define ISC_REFCOUNT_TRACE_DECL(name) \
+ name##_t *name##__ref(name##_t *ptr, const char *func, \
+ const char *file, unsigned int line); \
+ void name##__unref(name##_t *ptr, const char *func, const char *file, \
+ unsigned int line); \
+ void name##__attach(name##_t *ptr, name##_t **ptrp, const char *func, \
+ const char *file, unsigned int line); \
+ void name##__detach(name##_t **ptrp, const char *func, \
+ const char *file, unsigned int line)
+
+#define ISC_REFCOUNT_TRACE_IMPL(name, destroy) \
+ name##_t *name##__ref(name##_t *ptr, const char *func, \
+ const char *file, unsigned int line) { \
+ REQUIRE(ptr != NULL); \
+ uint_fast32_t refs = \
+ isc_refcount_increment(&ptr->references) + 1; \
+ fprintf(stderr, \
+ "%s:%s:%s:%u:%p->references = %" PRIuFAST32 "\n", \
+ __func__, func, file, line, ptr, refs); \
+ return (ptr); \
+ } \
+ \
+ void name##__unref(name##_t *ptr, const char *func, const char *file, \
+ unsigned int line) { \
+ REQUIRE(ptr != NULL); \
+ uint_fast32_t refs = \
+ isc_refcount_decrement(&ptr->references) - 1; \
+ if (refs == 0) { \
+ destroy(ptr); \
+ } \
+ fprintf(stderr, \
+ "%s:%s:%s:%u:%p->references = %" PRIuFAST32 "\n", \
+ __func__, func, file, line, ptr, refs); \
+ } \
+ void name##__attach(name##_t *ptr, name##_t **ptrp, const char *func, \
+ const char *file, unsigned int line) { \
+ REQUIRE(ptrp != NULL && *ptrp == NULL); \
+ uint_fast32_t refs = \
+ isc_refcount_increment(&ptr->references) + 1; \
+ fprintf(stderr, \
+ "%s:%s:%s:%u:%p->references = %" PRIuFAST32 "\n", \
+ __func__, func, file, line, ptr, refs); \
+ *ptrp = ptr; \
+ } \
+ \
+ void name##__detach(name##_t **ptrp, const char *func, \
+ const char *file, unsigned int line) { \
+ REQUIRE(ptrp != NULL && *ptrp != NULL); \
+ name##_t *ptr = *ptrp; \
+ *ptrp = NULL; \
+ uint_fast32_t refs = \
+ isc_refcount_decrement(&ptr->references) - 1; \
+ if (refs == 0) { \
+ destroy(ptr); \
+ } \
+ fprintf(stderr, \
+ "%s:%s:%s:%u:%p->references = %" PRIuFAST32 "\n", \
+ __func__, func, file, line, ptr, refs); \
+ }
+
+#define ISC_REFCOUNT_DECL(name) \
+ name##_t *name##_ref(name##_t *ptr); \
+ void name##_unref(name##_t *ptr); \
+ void name##_attach(name##_t *ptr, name##_t **ptrp); \
+ void name##_detach(name##_t **ptrp)
+
+#define ISC_REFCOUNT_IMPL(name, destroy) \
+ name##_t *name##_ref(name##_t *ptr) { \
+ REQUIRE(ptr != NULL); \
+ isc_refcount_increment(&ptr->references); \
+ return (ptr); \
+ } \
+ \
+ void name##_unref(name##_t *ptr) { \
+ REQUIRE(ptr != NULL); \
+ if (isc_refcount_decrement(&ptr->references) == 1) { \
+ destroy(ptr); \
+ } \
+ } \
+ void name##_attach(name##_t *ptr, name##_t **ptrp) { \
+ REQUIRE(ptrp != NULL && *ptrp == NULL); \
+ name##_ref(ptr); \
+ *ptrp = ptr; \
+ } \
+ \
+ void name##_detach(name##_t **ptrp) { \
+ REQUIRE(ptrp != NULL && *ptrp != NULL); \
+ name##_t *ptr = *ptrp; \
+ *ptrp = NULL; \
+ name##_unref(ptr); \
+ }
+
+ISC_LANG_ENDDECLS
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