Add workqueue system

src/logid/util/worker_thread.cpp

@@ -0,0 +1,88 @@
+/*
+ * Copyright 2019-2020 PixlOne
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+#include <vector>
+#include "worker_thread.h"
+#include "log.h"
+#include "workqueue.h"
+
+using namespace logid;
+
+worker_thread::worker_thread(workqueue* parent, std::size_t worker_number) :
+_parent (parent), _worker_number (worker_number), _continue_run (false),
+_thread (std::make_unique<thread> ([this](){
+    _run(); }, [this](std::exception& e){ _exception_handler(e); }))
+{
+    _thread->run();
+}
+
+worker_thread::~worker_thread()
+{
+    _continue_run = false;
+    _queue_cv.notify_all();
+    // Block until task is complete
+    std::unique_lock<std::mutex> lock(_busy);
+
+    while(!_queue.empty()) {
+        _parent->queue(_queue.front());
+        _queue.pop();
+    }
+}
+
+void worker_thread::queue(std::shared_ptr<task> t)
+{
+    _queue.push(t);
+    _queue_cv.notify_all();
+}
+
+bool worker_thread::busy()
+{
+    bool not_busy = _busy.try_lock();
+
+    if(not_busy)
+        _busy.unlock();
+
+    return !not_busy;
+}
+
+void worker_thread::_run()
+{
+    std::unique_lock<std::mutex> lock(_run_lock);
+    _continue_run = true;
+    while(_continue_run) {
+        _parent->busyUpdate();
+        _queue_cv.wait(lock, [this]{ return !_queue.empty() ||
+            !_continue_run; });
+        if(!_continue_run)
+            return;
+        std::unique_lock<std::mutex> busy_lock(_busy);
+        while(!_queue.empty()) {
+            _queue.front()->run();
+            _queue.pop();
+        }
+    }
+}
+
+void worker_thread::_exception_handler(std::exception &e)
+{
+    logPrintf(WARN, "Exception caught on worker thread %d, restarting: %s",
+            _worker_number, e.what());
+    // This action destroys the logid::thread, std::thread should detach safely.
+    _thread = std::make_unique<thread>([this](){ _run(); },
+            [this](std::exception& e) { _exception_handler(e); });
+    _thread->run();
+}