Add ConcurrentRun functions, and us one of them in gstenginepipeline with gstenginepipeline's own threadpool.

So now we can (finally!) play/pause/stop music while fingerprinting lot of songs or whatever else

ext/libclementine-common/core/concurrentrun.h

@@ -0,0 +1,134 @@
+/* This file is part of Clementine.
+   Copyright 2012, David Sansome <me@davidsansome.com>
+
+   Clementine 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.
+
+   Clementine 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 Clementine.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef THREADFUNCTION_H
+#define THREADFUNCTION_H
+
+#include <tr1/functional>
+
+#include <QFuture>
+#include <QRunnable>
+#include <QThreadPool>
+
+/*
+  The aim of ThreadFunctor classes and ConcurrentRun::Run() functions is to
+  complete QtConcurrentRun, which lack support of using a particular
+  QThreadPool, as it always uses QThreadPool::globalInstance().
+
+  This is problematic when we do not want to share the same thread pool over
+  all the application, but want to keep the convenient QtConcurrent::run()
+  functor syntax: time critical changes are performed in their own pool, which
+  is not empty by other actions, like when using QtConcurrentRun::run()
+
+  ThreadFunctor classes are used to store a functor and its arguments, and
+  Run() functions are used for convenience: to directly create a new
+  ThreadFunctor object and start it.
+
+  Currently, only functions with two arguments and a return value are
+  supported, but other might be added easily for X arguments by defining a new
+  ThreadFunctorBasX class, and add new Run() function.
+*/
+
+template<typename ReturnType>
+class ThreadFunctorBase : public QFutureInterface<ReturnType>, public QRunnable {
+ public:
+  ThreadFunctorBase() {}
+
+  QFuture<ReturnType> Start(QThreadPool* thread_pool) {
+    this->setRunnable(this);
+    this->reportStarted();
+    Q_ASSERT(thread_pool);
+    QFuture<ReturnType> future = this->future();
+    thread_pool->start(this, 0 /* priority: currently we do not support
+                                  changing the priority. Might be added later
+                                  if needed */);
+    return future;
+  }
+
+  virtual void run() = 0;
+
+  void End() {
+    this->reportResult(result_);
+    this->reportFinished();
+  }
+
+ protected:
+  ReturnType result_;
+};
+
+template<typename ReturnType, typename Arg>
+class ThreadFunctor1 : public ThreadFunctorBase<ReturnType> {
+public:
+  ThreadFunctor1(std::tr1::function<ReturnType (Arg)> function,
+                const Arg& arg)
+    : function_(function),
+      arg_(arg)
+  { }
+
+  void run() {
+    this->result_ = function_(arg_);
+    ThreadFunctorBase<ReturnType>::End();
+  }
+
+private:
+  std::tr1::function<ReturnType (Arg)> function_;
+  Arg arg_;
+};
+
+template<typename ReturnType, typename Arg1, typename Arg2>
+class ThreadFunctor2 : public ThreadFunctorBase<ReturnType> {
+public:
+  ThreadFunctor2(std::tr1::function<ReturnType (Arg1, Arg2)> function,
+                const Arg1& arg1, const Arg2& arg2)
+    : function_(function),
+      arg1_(arg1),
+      arg2_(arg2)
+  { }
+
+  void run() {
+    this->result_ = function_(arg1_, arg2_);
+    ThreadFunctorBase<ReturnType>::End();
+  }
+
+private:
+  std::tr1::function<ReturnType (Arg1, Arg2)> function_;
+  Arg1 arg1_;
+  Arg2 arg2_;
+};
+
+namespace ConcurrentRun {
+
+  template<typename ReturnType, typename Arg>
+  QFuture<ReturnType> Run(
+      QThreadPool* threadpool,
+      std::tr1::function<ReturnType (Arg)> function,
+      const Arg& arg) {
+
+    return (new ThreadFunctor1<ReturnType, Arg>(function, arg))->Start(threadpool);
+  }
+
+  template<typename ReturnType, typename Arg1, typename Arg2>
+  QFuture<ReturnType> Run(
+      QThreadPool* threadpool,
+      std::tr1::function<ReturnType (Arg1, Arg2)> function,
+      const Arg1& arg1, const Arg2& arg2) {
+
+    return (new ThreadFunctor2<ReturnType, Arg1, Arg2>(function, arg1, arg2))->Start(threadpool);
+  }
+}
+
+#endif // THREADFUNCTION_H

tests/concurrentrun_test.cpp

@@ -0,0 +1,30 @@
+#include "gtest/gtest.h"
+
+#include <QtGlobal>
+#include <QEventLoop>
+#include <QFutureWatcher>
+#include <QThreadPool>
+
+#include "core/concurrentrun.h"
+#include "test_utils.h"
+
+int max(int i, int j) {
+  return (i > j ? i : j);
+}
+
+TEST(ConcurrentRunTest, ConcurrentRunStartAndWait) {
+  int i = 10;
+  int j = 42;
+  QThreadPool threadpool;
+  QFuture<int> future = ConcurrentRun::Run<int, int, int>(&threadpool, &max, i, j);
+  QFutureWatcher<int> watcher;
+  watcher.setFuture(future);
+  QEventLoop loop;
+  QObject::connect(&watcher, SIGNAL(finished()), &loop, SLOT(quit()));
+  loop.exec();
+  EXPECT_EQ(42, watcher.result());
+}
+
+// TODO: add some more complex test cases? (e.g. with several CPU-consuming
+// tasks launched in parallel, with/without threadpool's threads numbers
+// decreased, etc.)