Thread pool can now receive tasks to do

src/thread_pool.cpp

@@ -49,7 +49,6 @@ void thread_pool::init()
 	num_finished_threads_ = 0u;
 	ready_for_work_ = false;
 	work_ = nullptr;
-	done_ = false;
 }
 
 void thread_pool::thread_proc()
@@ -75,7 +74,6 @@ void thread_pool::thread_proc()
 		lock.lock();
 		++num_finished_threads_;
 		if(num_finished_threads_ == NUM_THREADS) {
-			done_ = true;
 			done_promise_.set_value();
 			work_ = nullptr;
 		}

src/thread_pool.hpp

@@ -13,6 +13,7 @@
 
 #pragma once
 
+#include <atomic>
 #include <condition_variable>
 #include <functional>
 #include <future>
@@ -22,14 +23,27 @@
 
 class thread_pool
 {
+public:
 	thread_pool();
 	~thread_pool();
 
+	/** Runs the given workload.
+	@param work Container that contains objects to modify.
+	Can be a std::vector, std::array or std::deque.
+	@param func Function to call for every element in the container.
+	The function is assumed to edit the object in-place.
+	@return Future that becomes available when the task has finished. */
+	template<typename W, typename F>
+	std::future<void> run(W& work, F func);
+
 private:
 	const unsigned int NUM_THREADS = 16u;
 
 	void thread_proc();
 
+	template<typename W, typename F>
+	void worker(W& work, F func);
+
 	void init();
 
 	std::vector<std::thread> threads_;
@@ -40,7 +54,41 @@ class thread_pool
 	bool ready_for_work_;
 	std::condition_variable ready_for_work_cond_;
 	std::condition_variable work_cond_;
-	bool done_;
 	std::promise<void> done_promise_;
 	bool exiting_;
+	std::atomic<unsigned int> counter_;
 };
+
+template<typename W, typename F>
+std::future<void> thread_pool::run(W& work, F func)
+{
+	std::unique_lock<std::mutex> lock(mutex_);
+
+	// There must not be existing ongoing work.
+	assert(!work_);
+
+	while(!ready_for_work_) {
+		ready_for_work_cond_.wait(lock);
+	}
+
+	work_ = std::bind(&thread_pool::worker<W,F>, this, std::ref(work), func);
+	counter_ = 0u;
+	done_promise_ = std::promise<void>();
+	work_cond_.notify_all();
+
+	return done_promise_.get_future();
+}
+
+template<typename W, typename F>
+void thread_pool::worker(W& work, F func)
+{
+	// Note that fetch_add() returns the previous value.
+	// Thus, this returns zero for the first worker like it should.
+	std::atomic<unsigned int> index = counter_.fetch_add(1u,
+		std::memory_order::memory_order_relaxed);
+
+	while(index < work.size()) {
+		func(work[index]);
+		index = counter_.fetch_add(1u, std::memory_order::memory_order_relaxed);
+	}
+}