godot/core/os/safe_binary_mutex.h

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/**************************************************************************/
/* safe_binary_mutex.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_BINARY_MUTEX_H
#define SAFE_BINARY_MUTEX_H
#include "core/error/error_macros.h"
#include "core/os/mutex.h"
#include "core/typedefs.h"
#ifdef THREADS_ENABLED
// A very special kind of mutex, used in scenarios where these
// requirements hold at the same time:
// - Must be used with a condition variable (only binary mutexes are suitable).
// - Must have recursive semnantics (or simulate, as this one does).
// The implementation keeps the lock count in TS. Therefore, only
// one object of each version of the template can exists; hence the Tag argument.
// Tags must be unique across the Godot codebase.
// Also, don't forget to declare the thread_local variable on each use.
template <int Tag>
class SafeBinaryMutex {
friend class MutexLock<SafeBinaryMutex>;
using StdMutexType = THREADING_NAMESPACE::mutex;
mutable THREADING_NAMESPACE::mutex mutex;
static thread_local uint32_t count;
public:
_ALWAYS_INLINE_ void lock() const {
if (++count == 1) {
mutex.lock();
}
}
_ALWAYS_INLINE_ void unlock() const {
DEV_ASSERT(count);
if (--count == 0) {
mutex.unlock();
}
}
_ALWAYS_INLINE_ bool try_lock() const {
if (count) {
count++;
return true;
} else {
if (mutex.try_lock()) {
count++;
return true;
} else {
return false;
}
}
}
~SafeBinaryMutex() {
DEV_ASSERT(!count);
}
};
// This specialization is needed so manual locking and MutexLock can be used
// at the same time on a SafeBinaryMutex.
template <int Tag>
class MutexLock<SafeBinaryMutex<Tag>> {
friend class ConditionVariable;
THREADING_NAMESPACE::unique_lock<THREADING_NAMESPACE::mutex> lock;
public:
_ALWAYS_INLINE_ explicit MutexLock(const SafeBinaryMutex<Tag> &p_mutex) :
lock(p_mutex.mutex) {
SafeBinaryMutex<Tag>::count++;
};
_ALWAYS_INLINE_ ~MutexLock() {
SafeBinaryMutex<Tag>::count--;
};
};
#else // No threads.
template <int Tag>
class SafeBinaryMutex : public MutexImpl {
static thread_local uint32_t count;
};
template <int Tag>
class MutexLock<SafeBinaryMutex<Tag>> {
public:
MutexLock(const SafeBinaryMutex<Tag> &p_mutex) {}
~MutexLock() {}
};
#endif // THREADS_ENABLED
#endif // SAFE_BINARY_MUTEX_H