use threadpool for stuff

Makefile

@@ -5,7 +5,7 @@ all: vxorg tree_test
 clean:
 	rm vxorg tree_test *.o
 
-vxorg: vxorg.o vxheaven_parse.o
+vxorg: vxorg.o vxheaven_parse.o threadpool.o
 	$(CXX) $^ -o $@
 
 tree_test: tree_test.o
@@ -13,3 +13,10 @@ tree_test: tree_test.o
 
 %.o: %.cpp
 	$(CXX) -c $< -o $@
+
+
+# dep rules
+# I feel like it's 1970 again
+tree_test.o: tree.hpp
+vxorg.o: tree.hpp vxheaven_parse.hpp threadpool.hpp
+vxheaven_parse.o: tree.hpp vxheaven_parse.hpp

threadpool.cpp

@@ -0,0 +1,70 @@
+#include "threadpool.hpp"
+
+void ThreadPool::ThreadEntry(ThreadPool* pPool, std::size_t myIndex) {
+	auto& pool = *pPool;
+
+	// set a cutesy name
+#ifdef __linux__
+	pthread_setname_np(pthread_self(), "PoolWorker");
+#endif
+
+	// The thread loop
+	while(true) {
+		{
+			// wait for at least a single task, or shutdown notification (one of the two)
+			std::unique_lock lk(pool.taskQueues[myIndex].lock);
+			pool.queueCv.wait(lk, [&]() {
+				if(pool.threadsShouldShutdown)
+					return true;
+				return !pool.taskQueues[myIndex].queue.empty();
+			});
+		}
+
+		// Exit if the pool is to shutdown
+		if(pool.threadsShouldShutdown && pPool->QueueEmpty(myIndex))
+			break;
+
+		// pop and run tasks until we run out of tasks to run
+		{
+			std::unique_lock lk(pool.taskQueues[myIndex].lock);
+
+			// TODO: Work-steal from other threads.
+
+			while(!pool.taskQueues[myIndex].queue.empty()) {
+				auto& cb = pool.taskQueues[myIndex].queue.back();
+				cb();
+				pool.taskQueues[myIndex].queue.pop_back();
+			}
+		}
+	}
+
+}
+
+void ThreadPool::launch(std::size_t nrThreads) {
+	threadsShouldShutdown = false;
+	this->nrThreads = nrThreads;
+
+	threads.resize(this->nrThreads);
+	taskQueues = new TaskQueue[this->nrThreads];
+
+	for(std::size_t i = 0; i < this->nrThreads; ++i)
+		threads.emplace_back(std::thread(&ThreadEntry, this, i));
+}
+
+// Shutdown the thread pool
+void ThreadPool::shutdown() {
+	if(!threadsShouldShutdown)
+		threadsShouldShutdown = true;
+
+	queueCv.notify_all();
+
+	// join all the threads (if possible) to make sure they all exit
+	for(auto& thread : threads)
+		if(thread.joinable())
+			thread.join();
+
+    nrThreads = 0;
+
+	delete[] taskQueues;
+	taskQueues = nullptr;
+}

threadpool.hpp

@@ -0,0 +1,90 @@
+#include <atomic>
+#include <condition_variable>
+#include <cstddef>
+#include <cstdlib>
+#include <deque>
+#include <functional>
+#include <mutex>
+#include <thread>
+#include <vector>
+
+/// A simple thread pool executor.
+/// Not at all optimized, and probably terrible for latency.
+struct ThreadPool {
+	ThreadPool() = default;
+
+	// shorthand to call launch(nrThreads) automatically
+	inline explicit ThreadPool(std::size_t nrThreads) { launch(nrThreads); }
+
+	// move could be allowed, I guess
+	ThreadPool(const ThreadPool&) = delete;
+	ThreadPool(ThreadPool&&) = delete;
+
+	inline ~ThreadPool() { shutdown(); }
+
+	// takes anything that is callable with void() signature
+	// This includes capturable lambdas, so be careful or make sure you're locking state!
+	template <class Callable>
+	void add_task(Callable&& cb) {
+		auto worker = PickWorker();
+
+		//printf("picked worker %zu\n", worker);
+
+		// N.B: These wrappers still allow the thread to progress
+		if(QueueLength(worker) >= 4) {
+			//std::printf("queue for worker %zu too large. Blocking until it is empty\n", worker);
+			while(!QueueEmpty(worker)) {
+				std::this_thread::sleep_for(std::chrono::milliseconds(100));
+			}
+		}
+
+		// add it to the task queue for that thread
+		{
+			std::unique_lock lk(this->taskQueues[worker].lock);
+			taskQueues[worker].queue.push_front(cb);
+		}
+
+		// Wake threads up if they are waiting for work
+		queueCv.notify_all();
+	}
+
+	void launch(std::size_t nrThreads);
+	// Shutdown the thread pool
+	void shutdown();
+
+   private:
+	// could just use unique_ptr<T[]> for both of these,
+	// or an analogue, since they will only increase or decrease in size on a call to launch()
+	std::vector<std::thread> threads {}; // or analogue
+
+	std::size_t nrThreads = 0;
+
+	struct TaskQueue {
+		std::mutex lock {};
+		std::deque<std::function<void()>> queue {};
+	};
+
+	TaskQueue* taskQueues {};
+
+	// Used to notify threads when work is available or to shutdown
+	std::condition_variable queueCv {};
+
+	/// Used to notify on shutdown
+	std::atomic_bool threadsShouldShutdown { false };
+
+	std::size_t QueueLength(std::size_t worker) const {
+		std::unique_lock lk(this->taskQueues[worker].lock);
+		return this->taskQueues[worker].queue.size();
+	}
+
+	bool QueueEmpty(std::size_t worker) const {
+		std::unique_lock lk(this->taskQueues[worker].lock);
+		return this->taskQueues[worker].queue.empty();
+	}
+
+	std::size_t PickWorker() const {
+		return std::rand() % nrThreads;
+	}
+
+	static void ThreadEntry(ThreadPool* pPool, std::size_t myIndex);
+};

vxorg.cpp

@@ -5,6 +5,7 @@
 #include <string>
 
 #include "indicators/terminal_size.hpp"
+#include "threadpool.hpp"
 #include "tree.hpp"
 #include "vxheaven_parse.hpp"
 
@@ -14,6 +15,9 @@ int main() {
 	std::ifstream ifs("./testdata/samples.sort");
 	vxorg::VxHeavenTree tree;
 
+	// used for os filesystem ops
+	ThreadPool fsPool(4);
+
 	vxorg::parse_into_tree(tree, ifs);
 
 	std::filesystem::path root = std::filesystem::current_path() / "testdata";
@@ -66,7 +70,6 @@ int main() {
 #endif
 
 #if 1
-
 		if(!node->is_root()) {
 			if(data.is_sample) {
 				std::string sample_name = vxorg::get_sample_name(node);
@@ -79,23 +82,28 @@ int main() {
 					std::printf("WARNING: sample %s/%s in tree (source disk file %s) does not exist\n", path.string().c_str(), sample_name.c_str(),
 								source_path.string().c_str());
 				} else {
-					if(!std::filesystem::exists(path)) {
-						std::filesystem::create_directories(path);
-					}
+					fsPool.add_task([path, source_path, sample_name, &bar]() {
+						bar.set_option(ind::option::PostfixText { std::format("Moving {}", sample_name) });
 
-					bar.set_option(ind::option::PostfixText { std::format("Moving {}", sample_name) });
+                        auto dest_path = path / sample_name;
 
-					// FIXME Make this a move
-					std::filesystem::copy_file(source_path, path / vxorg::get_sample_name(node));
+                        // possibly TOCTOUable but it should:tm: be fine?
+                        if(!std::filesystem::exists(path)) {
+    						std::filesystem::create_directories(path);
+					    }
 
-					bar.tick();
+                        if(std::filesystem::exists(dest_path)) {
+                            std::filesystem::remove(dest_path);
+                        }
+
+						std::filesystem::rename(source_path, dest_path);
+						bar.tick();
+					});
 				}
-
-				// std::printf("sample %s/%s in tree (source disk file %s)\n", path.string().c_str(), sample_name.c_str(),
-				// source_path.string().c_str());
 			}
 		}
 #endif
 	});
+
 	return 0;
 }