Merge pip2

lib/main/thread/piexecutor.h

@@ -0,0 +1,111 @@
+/*
+	PIP - Platform Independent Primitives
+	
+	Stephan Fomenko
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU Lesser General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU Lesser General Public License for more details.
+
+	You should have received a copy of the GNU Lesser General Public License
+	along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef PIEXECUTOR_H
+#define PIEXECUTOR_H
+
+#include "piblockingdequeue.h"
+#include <atomic>
+
+/**
+ * @brief Thread pools address two different problems: they usually provide improved performance when executing large
+ * numbers of asynchronous tasks, due to reduced per-task invocation overhead, and they provide a means of bounding and
+ * managing the resources, including threads, consumed when executing a collection of tasks.
+ *
+ * TODO adapt documentation to template
+ */
+template <typename Thread_, typename Dequeue_>
+class PIThreadPoolExecutorTemplate {
+public:
+	explicit PIThreadPoolExecutorTemplate(size_t corePoolSize = 1) : isShutdown_(false) { makePool(corePoolSize); }
+
+	virtual ~PIThreadPoolExecutorTemplate() {
+		shutdownNow();
+		while (threadPool.size() > 0) delete threadPool.take_back();
+	}
+
+	/**
+	 * @brief Executes the given task sometime in the future. The task execute in an existing pooled thread. If the task
+	 * cannot be submitted for execution, either because this executor has been shutdown or because its capacity has been
+	 * reached.
+	 *
+	 * @param runnable not empty function for thread pool execution
+	 */
+	void execute(const std::function<void()> & runnable) {
+		if (!isShutdown_) taskQueue.offer(runnable);
+	}
+
+	/**
+	 * @brief Initiates an orderly shutdown in which previously submitted tasks are executed, but no new tasks will be
+	 * accepted. Invocation has no additional effect if already shut down. This method does not wait for previously
+	 * submitted tasks to complete execution. Use awaitTermination to do that.
+	 */
+	void shutdown() {
+		isShutdown_ = true;
+	}
+
+	void shutdownNow() {
+		isShutdown_ = true;
+		for (size_t i = 0; i < threadPool.size(); ++i) threadPool[i]->stop();
+	}
+
+	bool isShutdown() const {
+		return isShutdown_;
+	}
+
+	bool awaitTermination(int timeoutMs) {
+		PITimeMeasurer measurer;
+		for (size_t i = 0; i < threadPool.size(); ++i) {
+			int dif = timeoutMs - (int)measurer.elapsed_m();
+			if (dif < 0) return false;
+			if (!threadPool[i]->waitForFinish(dif)) return false;
+		}
+		return true;
+	}
+
+protected:
+	std::atomic_bool isShutdown_;
+	Dequeue_ taskQueue;
+	PIVector<Thread_*> threadPool;
+
+	template<typename Function>
+	PIThreadPoolExecutorTemplate(size_t corePoolSize, Function onBeforeStart) : isShutdown_(false) {
+		makePool(corePoolSize, onBeforeStart);
+	}
+
+	void makePool(size_t corePoolSize, std::function<void(Thread_*)> onBeforeStart = [](Thread_*){}) {
+		for (size_t i = 0; i < corePoolSize; ++i) {
+			auto* thread = new Thread_([&, i](){
+				auto runnable = taskQueue.poll(100);
+				if (runnable) {
+					runnable();
+				}
+				if (isShutdown_ && taskQueue.size() == 0) threadPool[i]->stop();
+			});
+			threadPool.push_back(thread);
+			onBeforeStart(thread);
+			thread->start();
+		}
+	}
+};
+
+typedef PIThreadPoolExecutorTemplate<PIThread, PIBlockingDequeue<std::function<void()> > > PIThreadPoolExecutor;
+
+
+#endif //PIEXECUTOR_H