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