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212 lines
6.2 KiB
C++
212 lines
6.2 KiB
C++
/*************************************************************************/
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/* safe_refcount.h */
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/*************************************************************************/
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/* This file is part of: */
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/* GODOT ENGINE */
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/* https://godotengine.org */
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/*************************************************************************/
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/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur. */
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/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md). */
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/* */
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/* Permission is hereby granted, free of charge, to any person obtaining */
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/* a copy of this software and associated documentation files (the */
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/* "Software"), to deal in the Software without restriction, including */
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/* without limitation the rights to use, copy, modify, merge, publish, */
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/* distribute, sublicense, and/or sell copies of the Software, and to */
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/* permit persons to whom the Software is furnished to do so, subject to */
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/* the following conditions: */
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/* */
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/* The above copyright notice and this permission notice shall be */
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/* included in all copies or substantial portions of the Software. */
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/* */
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/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
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/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
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/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
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/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
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/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
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/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
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/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
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/*************************************************************************/
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#ifndef SAFE_REFCOUNT_H
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#define SAFE_REFCOUNT_H
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#include "core/os/mutex.h"
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#include "core/typedefs.h"
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#include "platform_config.h"
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// Atomic functions, these are used for multithread safe reference counters!
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#ifdef NO_THREADS
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/* Bogus implementation unaware of multiprocessing */
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template <class T>
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static _ALWAYS_INLINE_ T atomic_conditional_increment(volatile T *pw) {
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if (*pw == 0)
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return 0;
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(*pw)++;
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return *pw;
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}
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template <class T>
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static _ALWAYS_INLINE_ T atomic_decrement(volatile T *pw) {
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(*pw)--;
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return *pw;
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}
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template <class T>
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static _ALWAYS_INLINE_ T atomic_increment(volatile T *pw) {
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(*pw)++;
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return *pw;
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}
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template <class T, class V>
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static _ALWAYS_INLINE_ T atomic_sub(volatile T *pw, volatile V val) {
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(*pw) -= val;
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return *pw;
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}
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template <class T, class V>
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static _ALWAYS_INLINE_ T atomic_add(volatile T *pw, volatile V val) {
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(*pw) += val;
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return *pw;
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}
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template <class T, class V>
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static _ALWAYS_INLINE_ T atomic_exchange_if_greater(volatile T *pw, volatile V val) {
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if (val > *pw)
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*pw = val;
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return *pw;
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}
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#elif defined(__GNUC__)
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/* Implementation for GCC & Clang */
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// GCC guarantees atomic intrinsics for sizes of 1, 2, 4 and 8 bytes.
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// Clang states it supports GCC atomic builtins.
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template <class T>
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static _ALWAYS_INLINE_ T atomic_conditional_increment(volatile T *pw) {
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while (true) {
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T tmp = static_cast<T const volatile &>(*pw);
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if (tmp == 0)
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return 0; // if zero, can't add to it anymore
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if (__sync_val_compare_and_swap(pw, tmp, tmp + 1) == tmp)
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return tmp + 1;
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}
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}
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template <class T>
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static _ALWAYS_INLINE_ T atomic_decrement(volatile T *pw) {
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return __sync_sub_and_fetch(pw, 1);
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}
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template <class T>
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static _ALWAYS_INLINE_ T atomic_increment(volatile T *pw) {
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return __sync_add_and_fetch(pw, 1);
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}
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template <class T, class V>
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static _ALWAYS_INLINE_ T atomic_sub(volatile T *pw, volatile V val) {
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return __sync_sub_and_fetch(pw, val);
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}
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template <class T, class V>
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static _ALWAYS_INLINE_ T atomic_add(volatile T *pw, volatile V val) {
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return __sync_add_and_fetch(pw, val);
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}
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template <class T, class V>
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static _ALWAYS_INLINE_ T atomic_exchange_if_greater(volatile T *pw, volatile V val) {
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while (true) {
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T tmp = static_cast<T const volatile &>(*pw);
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if (tmp >= val)
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return tmp; // already greater, or equal
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if (__sync_val_compare_and_swap(pw, tmp, val) == tmp)
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return val;
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}
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}
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#elif defined(_MSC_VER)
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// For MSVC use a separate compilation unit to prevent windows.h from polluting
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// the global namespace.
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uint32_t atomic_conditional_increment(volatile uint32_t *pw);
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uint32_t atomic_decrement(volatile uint32_t *pw);
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uint32_t atomic_increment(volatile uint32_t *pw);
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uint32_t atomic_sub(volatile uint32_t *pw, volatile uint32_t val);
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uint32_t atomic_add(volatile uint32_t *pw, volatile uint32_t val);
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uint32_t atomic_exchange_if_greater(volatile uint32_t *pw, volatile uint32_t val);
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uint64_t atomic_conditional_increment(volatile uint64_t *pw);
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uint64_t atomic_decrement(volatile uint64_t *pw);
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uint64_t atomic_increment(volatile uint64_t *pw);
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uint64_t atomic_sub(volatile uint64_t *pw, volatile uint64_t val);
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uint64_t atomic_add(volatile uint64_t *pw, volatile uint64_t val);
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uint64_t atomic_exchange_if_greater(volatile uint64_t *pw, volatile uint64_t val);
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#else
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//no threads supported?
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#error Must provide atomic functions for this platform or compiler!
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#endif
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struct SafeRefCount {
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uint32_t count;
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public:
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// destroy() is called when weak_count_ drops to zero.
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_ALWAYS_INLINE_ bool ref() { // true on success
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return atomic_conditional_increment(&count) != 0;
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}
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_ALWAYS_INLINE_ uint32_t refval() { // none-zero on success
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return atomic_conditional_increment(&count);
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}
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_ALWAYS_INLINE_ bool unref() { // true if must be disposed of
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return atomic_decrement(&count) == 0;
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}
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_ALWAYS_INLINE_ uint32_t unrefval() { // 0 if must be disposed of
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return atomic_decrement(&count);
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}
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_ALWAYS_INLINE_ uint32_t get() const { // nothrow
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return count;
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}
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_ALWAYS_INLINE_ void init(uint32_t p_value = 1) {
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count = p_value;
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}
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};
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#endif // SAFE_REFCOUNT_H
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