thread/dispatcher.cc

A Glib::Dispatcher example.

/*
* Glib::Dispatcher example -- cross thread signalling
* by Daniel Elstner <daniel.kitta@gmail.com>
*
* modified to only use glibmm
* by J. Abelardo Gutierrez <jabelardo@cantv.net>
*
* Copyright (c) 2002-2003 Free Software Foundation
*/
#include <glibmm.h>
#include <algorithm>
#include <functional>
#include <iostream>
#include <thread>
#include <vector>
namespace
{
/*
* Note that it does not make sense for this class to inherit from
* sigc::trackable, as doing so would only give a false sense of security.
* Once the thread launch has been triggered, the object has to stay alive
* until the thread has been joined again. The code running in the thread
* assumes the existence of the object. If it is destroyed earlier, the
* program will crash, with sigc::trackable or without it.
*/
class ThreadProgress
{
public:
explicit ThreadProgress(int the_id);
~ThreadProgress();
int id() const;
void launch();
void join();
bool unfinished() const;
sigc::signal<void()>& signal_finished();
private:
enum
{
ITERATIONS = 100
};
// Note that the thread does not write to the member data at all. It only
// reads signal_increment_, which is only written to before the thread is
// launched. Therefore, no locking is required.
std::thread* thread_;
int id_;
unsigned int progress_;
Glib::Dispatcher signal_increment_;
sigc::signal<void()> signal_finished_;
void progress_increment();
void thread_function();
};
class Application : public sigc::trackable
{
public:
Application();
~Application();
void run();
private:
Glib::RefPtr<Glib::MainLoop> main_loop_;
std::vector<ThreadProgress*> progress_threads_;
void launch_threads();
void on_progress_finished(ThreadProgress* thread_progress);
};
template <class T>
class DeletePtr : public std::unary_function<void, T>
{
public:
void operator()(T ptr) const { delete ptr; }
};
ThreadProgress::ThreadProgress(int the_id) : thread_(nullptr), id_(the_id), progress_(0)
{
// Connect to the cross-thread signal.
signal_increment_.connect(sigc::mem_fun(*this, &ThreadProgress::progress_increment));
}
ThreadProgress::~ThreadProgress()
{
// It is an error if the thread is still running at this point.
g_return_if_fail(thread_ == nullptr);
}
int
ThreadProgress::id() const
{
return id_;
}
void
ThreadProgress::launch()
{
// Create a joinable thread.
thread_ = new std::thread([this]() { thread_function(); });
}
void
ThreadProgress::join()
{
thread_->join();
delete thread_;
thread_ = nullptr;
}
bool
ThreadProgress::unfinished() const
{
return (progress_ < ITERATIONS);
}
sigc::signal<void()>&
ThreadProgress::signal_finished()
{
return signal_finished_;
}
void
ThreadProgress::progress_increment()
{
++progress_;
std::cout << "Thread " << id_ << ": " << progress_ << '%' << std::endl;
if (progress_ >= ITERATIONS)
signal_finished_();
}
void
ThreadProgress::thread_function()
{
Glib::Rand rand;
for (auto i = 0; i < ITERATIONS; ++i)
{
Glib::usleep(rand.get_int_range(2000, 20000));
// Tell the main thread to increment the progress value.
signal_increment_();
}
}
Application::Application() : main_loop_(Glib::MainLoop::create()), progress_threads_(5)
{
try
{
for (std::vector<ThreadProgress*>::size_type i = 0; i < progress_threads_.size(); ++i)
{
ThreadProgress* const progress = new ThreadProgress(i + 1);
progress_threads_[i] = progress;
progress->signal_finished().connect(
sigc::bind(sigc::mem_fun(*this, &Application::on_progress_finished), progress));
}
}
catch (...)
{
// In your own code, you should preferably use a smart pointer
// to ensure exception safety.
std::for_each(progress_threads_.begin(), progress_threads_.end(), DeletePtr<ThreadProgress*>());
throw;
}
}
Application::~Application()
{
std::for_each(progress_threads_.begin(), progress_threads_.end(), DeletePtr<ThreadProgress*>());
}
void
Application::run()
{
// Install a one-shot idle handler to launch the threads.
Glib::signal_idle().connect_once(sigc::mem_fun(*this, &Application::launch_threads));
main_loop_->run();
}
void
Application::launch_threads()
{
std::cout << "Launching " << progress_threads_.size() << " threads:" << std::endl;
std::for_each(
progress_threads_.begin(), progress_threads_.end(), std::mem_fun(&ThreadProgress::launch));
}
void
Application::on_progress_finished(ThreadProgress* thread_progress)
{
thread_progress->join();
std::cout << "Thread " << thread_progress->id() << ": finished." << std::endl;
// Quit if it was the last thread to be joined.
if (std::find_if(progress_threads_.begin(), progress_threads_.end(),
std::mem_fun(&ThreadProgress::unfinished)) == progress_threads_.end())
{
main_loop_->quit();
}
}
} // anonymous namespace
int
main(int, char**)
{
Glib::init();
Application application;
application.run();
return 0;
}