Port a bunch of Godot container templates to GDExtension.

1 files changed, 205 insertions, 0 deletions

diff --git a/include/godot_cpp/templates/thread_work_pool.hpp b/include/godot_cpp/templates/thread_work_pool.hpp
new file mode 100644
index 0000000..6a2051c
--- /dev/null
+++ b/include/godot_cpp/templates/thread_work_pool.hpp
@@ -0,0 +1,205 @@
+/*************************************************************************/
+/*  thread_work_pool.hpp                                                 */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2021 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 THREAD_WORK_POOL_HPP
+#define 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 <class C, class M, class 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 <class C, class M, class U>
+	void begin_work(uint32_t p_elements, C *p_instance, M p_method, U p_userdata) {
+		ERR_FAIL_COND(!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_COND_V(current_work == nullptr, true);
+		return index.load(std::memory_order_acquire) >= current_work->max_elements;
+	}
+
+	uint32_t get_work_index() const {
+		ERR_FAIL_COND_V(current_work == nullptr, 0);
+		uint32_t idx = index.load(std::memory_order_acquire);
+		return Math::min(idx, current_work->max_elements);
+	}
+
+	void end_work() {
+		ERR_FAIL_COND(current_work == nullptr);
+		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 <class C, class M, class 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 // ! THREAD_WORK_POOL_HPP