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/**************************************************************************/
/* thread_work_pool.hpp */
/**************************************************************************/
/* 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 GODOT_THREAD_WORK_POOL_HPP
#define GODOT_THREAD_WORK_POOL_HPP
#include <godot_cpp/classes/os.hpp>
#include <godot_cpp/classes/semaphore.hpp>
#include <godot_cpp/core/error_macros.hpp>
#include <godot_cpp/core/memory.hpp>
#include <thread>
#include <atomic>
namespace godot {
class ThreadWorkPool {
std::atomic<uint32_t> index;
struct BaseWork {
std::atomic<uint32_t> *index = nullptr;
uint32_t max_elements = 0;
virtual void work() = 0;
virtual ~BaseWork() = default;
};
template <typename C, typename M, typename U>
struct Work : public BaseWork {
C *instance;
M method;
U userdata;
virtual void work() {
while (true) {
uint32_t work_index = index->fetch_add(1, std::memory_order_relaxed);
if (work_index >= max_elements) {
break;
}
(instance->*method)(work_index, userdata);
}
}
};
struct ThreadData {
std::thread thread;
Semaphore start;
Semaphore completed;
std::atomic<bool> exit;
BaseWork *work;
};
ThreadData *threads = nullptr;
uint32_t thread_count = 0;
uint32_t threads_working = 0;
BaseWork *current_work = nullptr;
static void _thread_function(void *p_user) {
ThreadData *thread = static_cast<ThreadData *>(p_user);
while (true) {
thread->start.wait();
if (thread->exit.load()) {
break;
}
thread->work->work();
thread->completed.post();
}
}
public:
template <typename C, typename M, typename U>
void begin_work(uint32_t p_elements, C *p_instance, M p_method, U p_userdata) {
ERR_FAIL_NULL(threads); // Never initialized.
ERR_FAIL_COND(current_work != nullptr);
index.store(0, std::memory_order_release);
Work<C, M, U> *w = new (Work<C, M, U>);
w->instance = p_instance;
w->userdata = p_userdata;
w->method = p_method;
w->index = &index;
w->max_elements = p_elements;
current_work = w;
threads_working = Math::min(p_elements, thread_count);
for (uint32_t i = 0; i < threads_working; i++) {
threads[i].work = w;
threads[i].start.post();
}
}
bool is_working() const {
return current_work != nullptr;
}
bool is_done_dispatching() const {
ERR_FAIL_NULL_V(current_work, true);
return index.load(std::memory_order_acquire) >= current_work->max_elements;
}
uint32_t get_work_index() const {
ERR_FAIL_NULL_V(current_work, 0);
uint32_t idx = index.load(std::memory_order_acquire);
return Math::min(idx, current_work->max_elements);
}
void end_work() {
ERR_FAIL_NULL(current_work);
for (uint32_t i = 0; i < threads_working; i++) {
threads[i].completed.wait();
threads[i].work = nullptr;
}
threads_working = 0;
delete current_work;
current_work = nullptr;
}
template <typename C, typename M, typename U>
void do_work(uint32_t p_elements, C *p_instance, M p_method, U p_userdata) {
switch (p_elements) {
case 0:
// Nothing to do, so do nothing.
break;
case 1:
// No value in pushing the work to another thread if it's a single job
// and we're going to wait for it to finish. Just run it right here.
(p_instance->*p_method)(0, p_userdata);
break;
default:
// Multiple jobs to do; commence threaded business.
begin_work(p_elements, p_instance, p_method, p_userdata);
end_work();
}
}
_FORCE_INLINE_ int get_thread_count() const { return thread_count; }
void init(int p_thread_count = -1) {
ERR_FAIL_COND(threads != nullptr);
if (p_thread_count < 0) {
p_thread_count = OS::get_singleton()->get_processor_count();
}
thread_count = p_thread_count;
threads = new ThreadData[thread_count];
for (uint32_t i = 0; i < thread_count; i++) {
threads[i].exit.store(false);
threads[i].thread = std::thread(&ThreadWorkPool::_thread_function, &threads[i]);
}
}
void finish() {
if (threads == nullptr) {
return;
}
for (uint32_t i = 0; i < thread_count; i++) {
threads[i].exit.store(true);
threads[i].start.post();
}
for (uint32_t i = 0; i < thread_count; i++) {
threads[i].thread.join();
}
delete[] (threads);
threads = nullptr;
}
~ThreadWorkPool() {
finish();
}
};
} // namespace godot
#endif // GODOT_THREAD_WORK_POOL_HPP
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