mirror of
https://github.com/godotengine/godot.git
synced 2024-11-22 04:06:14 +00:00
227 lines
7.5 KiB
C++
227 lines
7.5 KiB
C++
/**************************************************************************/
|
|
/* safe_refcount.h */
|
|
/**************************************************************************/
|
|
/* This file is part of: */
|
|
/* GODOT ENGINE */
|
|
/* https://godotengine.org */
|
|
/**************************************************************************/
|
|
/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
|
|
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur. */
|
|
/* */
|
|
/* 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/typedefs.h"
|
|
|
|
#ifdef DEV_ENABLED
|
|
#include "core/error/error_macros.h"
|
|
#endif
|
|
|
|
#include <atomic>
|
|
#include <type_traits>
|
|
|
|
// Design goals for these classes:
|
|
// - No automatic conversions or arithmetic operators,
|
|
// to keep explicit the use of atomics everywhere.
|
|
// - Using acquire-release semantics, even to set the first value.
|
|
// The first value may be set relaxedly in many cases, but adding the distinction
|
|
// between relaxed and unrelaxed operation to the interface would make it needlessly
|
|
// flexible. There's negligible waste in having release semantics for the initial
|
|
// value and, as an important benefit, you can be sure the value is properly synchronized
|
|
// even with threads that are already running.
|
|
|
|
// These are used in very specific areas of the engine where it's critical that these guarantees are held
|
|
#define SAFE_NUMERIC_TYPE_PUN_GUARANTEES(m_type) \
|
|
static_assert(sizeof(SafeNumeric<m_type>) == sizeof(m_type)); \
|
|
static_assert(alignof(SafeNumeric<m_type>) == alignof(m_type)); \
|
|
static_assert(std::is_trivially_destructible_v<std::atomic<m_type>>);
|
|
#define SAFE_FLAG_TYPE_PUN_GUARANTEES \
|
|
static_assert(sizeof(SafeFlag) == sizeof(bool)); \
|
|
static_assert(alignof(SafeFlag) == alignof(bool));
|
|
|
|
template <typename T>
|
|
class SafeNumeric {
|
|
std::atomic<T> value;
|
|
|
|
static_assert(std::atomic<T>::is_always_lock_free);
|
|
|
|
public:
|
|
_ALWAYS_INLINE_ void set(T p_value) {
|
|
value.store(p_value, std::memory_order_release);
|
|
}
|
|
|
|
_ALWAYS_INLINE_ T get() const {
|
|
return value.load(std::memory_order_acquire);
|
|
}
|
|
|
|
_ALWAYS_INLINE_ T increment() {
|
|
return value.fetch_add(1, std::memory_order_acq_rel) + 1;
|
|
}
|
|
|
|
// Returns the original value instead of the new one
|
|
_ALWAYS_INLINE_ T postincrement() {
|
|
return value.fetch_add(1, std::memory_order_acq_rel);
|
|
}
|
|
|
|
_ALWAYS_INLINE_ T decrement() {
|
|
return value.fetch_sub(1, std::memory_order_acq_rel) - 1;
|
|
}
|
|
|
|
// Returns the original value instead of the new one
|
|
_ALWAYS_INLINE_ T postdecrement() {
|
|
return value.fetch_sub(1, std::memory_order_acq_rel);
|
|
}
|
|
|
|
_ALWAYS_INLINE_ T add(T p_value) {
|
|
return value.fetch_add(p_value, std::memory_order_acq_rel) + p_value;
|
|
}
|
|
|
|
// Returns the original value instead of the new one
|
|
_ALWAYS_INLINE_ T postadd(T p_value) {
|
|
return value.fetch_add(p_value, std::memory_order_acq_rel);
|
|
}
|
|
|
|
_ALWAYS_INLINE_ T sub(T p_value) {
|
|
return value.fetch_sub(p_value, std::memory_order_acq_rel) - p_value;
|
|
}
|
|
|
|
_ALWAYS_INLINE_ T bit_or(T p_value) {
|
|
return value.fetch_or(p_value, std::memory_order_acq_rel);
|
|
}
|
|
_ALWAYS_INLINE_ T bit_and(T p_value) {
|
|
return value.fetch_and(p_value, std::memory_order_acq_rel);
|
|
}
|
|
|
|
_ALWAYS_INLINE_ T bit_xor(T p_value) {
|
|
return value.fetch_xor(p_value, std::memory_order_acq_rel);
|
|
}
|
|
|
|
// Returns the original value instead of the new one
|
|
_ALWAYS_INLINE_ T postsub(T p_value) {
|
|
return value.fetch_sub(p_value, std::memory_order_acq_rel);
|
|
}
|
|
|
|
_ALWAYS_INLINE_ T exchange_if_greater(T p_value) {
|
|
while (true) {
|
|
T tmp = value.load(std::memory_order_acquire);
|
|
if (tmp >= p_value) {
|
|
return tmp; // already greater, or equal
|
|
}
|
|
|
|
if (value.compare_exchange_weak(tmp, p_value, std::memory_order_acq_rel)) {
|
|
return p_value;
|
|
}
|
|
}
|
|
}
|
|
|
|
_ALWAYS_INLINE_ T conditional_increment() {
|
|
while (true) {
|
|
T c = value.load(std::memory_order_acquire);
|
|
if (c == 0) {
|
|
return 0;
|
|
}
|
|
if (value.compare_exchange_weak(c, c + 1, std::memory_order_acq_rel)) {
|
|
return c + 1;
|
|
}
|
|
}
|
|
}
|
|
|
|
_ALWAYS_INLINE_ explicit SafeNumeric(T p_value = static_cast<T>(0)) {
|
|
set(p_value);
|
|
}
|
|
};
|
|
|
|
class SafeFlag {
|
|
std::atomic_bool flag;
|
|
|
|
static_assert(std::atomic_bool::is_always_lock_free);
|
|
|
|
public:
|
|
_ALWAYS_INLINE_ bool is_set() const {
|
|
return flag.load(std::memory_order_acquire);
|
|
}
|
|
|
|
_ALWAYS_INLINE_ void set() {
|
|
flag.store(true, std::memory_order_release);
|
|
}
|
|
|
|
_ALWAYS_INLINE_ void clear() {
|
|
flag.store(false, std::memory_order_release);
|
|
}
|
|
|
|
_ALWAYS_INLINE_ void set_to(bool p_value) {
|
|
flag.store(p_value, std::memory_order_release);
|
|
}
|
|
|
|
_ALWAYS_INLINE_ explicit SafeFlag(bool p_value = false) {
|
|
set_to(p_value);
|
|
}
|
|
};
|
|
|
|
class SafeRefCount {
|
|
SafeNumeric<uint32_t> count;
|
|
|
|
#ifdef DEV_ENABLED
|
|
_ALWAYS_INLINE_ void _check_unref_safety() {
|
|
// This won't catch every misuse, but it's better than nothing.
|
|
CRASH_COND_MSG(count.get() == 0,
|
|
"Trying to unreference a SafeRefCount which is already zero is wrong and a symptom of it being misused.\n"
|
|
"Upon a SafeRefCount reaching zero any object whose lifetime is tied to it, as well as the ref count itself, must be destroyed.\n"
|
|
"Moreover, to guarantee that, no multiple threads should be racing to do the final unreferencing to zero.");
|
|
}
|
|
#endif
|
|
|
|
public:
|
|
_ALWAYS_INLINE_ bool ref() { // true on success
|
|
return count.conditional_increment() != 0;
|
|
}
|
|
|
|
_ALWAYS_INLINE_ uint32_t refval() { // none-zero on success
|
|
return count.conditional_increment();
|
|
}
|
|
|
|
_ALWAYS_INLINE_ bool unref() { // true if must be disposed of
|
|
#ifdef DEV_ENABLED
|
|
_check_unref_safety();
|
|
#endif
|
|
return count.decrement() == 0;
|
|
}
|
|
|
|
_ALWAYS_INLINE_ uint32_t unrefval() { // 0 if must be disposed of
|
|
#ifdef DEV_ENABLED
|
|
_check_unref_safety();
|
|
#endif
|
|
return count.decrement();
|
|
}
|
|
|
|
_ALWAYS_INLINE_ uint32_t get() const {
|
|
return count.get();
|
|
}
|
|
|
|
_ALWAYS_INLINE_ void init(uint32_t p_value = 1) {
|
|
count.set(p_value);
|
|
}
|
|
};
|
|
|
|
#endif // SAFE_REFCOUNT_H
|