3. Policy benutzen, um Threading-Verhalten in Klasse zu geben

Policy benutzen, um Threading-Verhalten in Klasse zu geben

  • P

    Das Problem ist, dass ich boost komplett wegkapseln muss, da der single-threaded teil des projekts kein boost zur verfügung hat.

    Daher darf in der Klasse kein boost-Code drinstehen, der muß über die Policy reinkommen. Das ging vorher halt über ein #ifdef.

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  • Administrator

    Dann schreib halt eben deinen eigenen Lock-Guard. Ist ja auch nicht weiters wild:

    template<typename MutexT>
class scoped_lock
{
private:
  MutexT& m_mutex;

public:
  scoped_lock(Mutex& mutex)
   : m_mutex(mutex)
  {
    m_mutex.lock();
  }

  ~scoped_lock()
  {
    m_mutex.unlock();
  }

private:
  scoped_lock(scoped_lock const&) { }
  scoped_lock& operator =(scoped_lock const&) { }
};

    Statt boost::lock_guard verwendest du halt nun scoped_lock .

    Grüssli

    0
  • P

    Das scheint genau das zu leisten, was ich brauche:

    #include <iostream>
#include <boost/thread.hpp>
#include <QMutexLocker>
using namespace std;

class BoostThreaded {
public:
    typedef boost::mutex Mutex;
    typedef boost::mutex::scoped_lock ScopedLock;
protected:
    Mutex lock_;
};

class QThreaded {
public:
    typedef QMutex Mutex;
    typedef QMutexLocker ScopedLock;
    QThreaded():lock_(new QMutex) {};
    ~QThreaded() { delete lock_; }
protected:
    Mutex* lock_;
};

class SingleThreaded {
public:
    typedef void* Mutex;
    typedef void* ScopedLock;
protected:
    Mutex lock_;
};

template <class ThreadingPolicy>
class Foo: public ThreadingPolicy {
public:
    typedef typename ThreadingPolicy::ScopedLock ScopedLock;
    using ThreadingPolicy::lock_;
    void bar() {
        ScopedLock lock(lock_);
        cout << "Bar!" << endl;
    }
};

int main(int argc, char *argv[])
{
    Foo<BoostThreaded> my_threaded_foo;
    my_threaded_foo.bar();

    Foo<QThreaded> my_qthreaded_foo;
    my_qthreaded_foo.bar();

    Foo<SingleThreaded> my_singlethreaded_foo;
    my_singlethreaded_foo.bar();

    return 0;
}

    Meinungen ?

    0
  • Administrator

    Wieso erbst du von der Policy?

    Grüssli

    0
  • P

    Ähm, weil ich das so gelernt habe?!
    Laut Alexandrescu ist policy-based design die Kombination von Mehrfachvererbung mit Templates durch das Erben von seinen Templateparametern. Wikipedia sieht das genauso.

    Philipp

    EDIT: Und so klappts auch mit der Nachbarin, ähh, der Wait-Condition:

    #include <iostream>
#include <boost/thread.hpp>
#include <QMutexLocker>
#include <QWaitCondition>
using namespace std;

class BoostThreaded {
public:
    typedef boost::mutex Mutex;
    typedef boost::mutex::scoped_lock ScopedLock;
    typedef boost::condition_variable WaitCondition;
    void wait(ScopedLock& lock) { condition_.wait(lock); }
    void notify() { condition_.notify_one(); }
protected:
    Mutex lock_;
    WaitCondition condition_;
};

class QThreaded {
public:
    typedef QMutex Mutex;
    typedef QMutexLocker ScopedLock;
    typedef QWaitCondition WaitCondition;
    void wait(ScopedLock&) { condition_.wait(lock_); }
    void notify() { condition_.wakeOne(); }
    QThreaded():lock_(new QMutex) {};
    ~QThreaded() { delete lock_; }
protected:
    Mutex* lock_;
    WaitCondition condition_;
};

class SingleThreaded {
public:
    typedef void* Mutex;
    typedef void* ScopedLock;
    void wait(ScopedLock&) {}
    void notify() {}
protected:
    Mutex lock_;
};

template <class ThreadingPolicy>
class Foo: public ThreadingPolicy {
public:
    typedef typename ThreadingPolicy::ScopedLock ScopedLock;
    using ThreadingPolicy::lock_;
    using ThreadingPolicy::wait;
    using ThreadingPolicy::notify;
    void bar() {
        ScopedLock lock(lock_);
        cout << "Bar!" << endl;
        wait(lock);
        notify();
    }
};

int main(int argc, char *argv[])
{
    Foo<BoostThreaded> my_threaded_foo;
    my_threaded_foo.bar();

    Foo<QThreaded> my_qthreaded_foo;
    my_qthreaded_foo.bar();

    Foo<SingleThreaded> my_singlethreaded_foo;
    my_singlethreaded_foo.bar();

    return 0;
}
    0
  • V

    Dravere schrieb:

    Wieso erbst du von der Policy?

    Erben muß nicht sein, und eigentlich denke ich, daß es hier böse ist.
    Aber die "Empty Member" Optimization http://www.cantrip.org/emptyopt.html greift da so schön.

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  • P

    Aber wie soll ich sonst an die mutex-membervariable drankommen? Dann müsste ich ja Foo zum friend jeder Policy machen, bzw die Policy selbst wieder zum template, damit T ihr friend sein kann, damit er auf mutex_ zugreifen kann.

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  • V

    PhilippM schrieb:

    Aber wie soll ich sonst an die mutex-membervariable drankommen? Dann müsste ich ja Foo zum friend jeder Policy machen, bzw die Policy selbst wieder zum template, damit T ihr friend sein kann, damit er auf mutex_ zugreifen kann.

    Policies sind so klein und simpel, da dard ein Attribut auch mal pubnlic sein.

    0
  • P

    na dann 🙂

    0
  • P

    Dann präsentiere ich hier die parametrierbare concurrent-queue:

    #include <iostream>
#include <queue>
#include <boost/thread.hpp>
#include <QMutexLocker>
#include <QWaitCondition>
using namespace std;

class BoostThreaded {
public:
    typedef boost::mutex Mutex;
    typedef boost::mutex::scoped_lock ScopedLock;
    typedef boost::condition_variable WaitCondition;
    void wait(ScopedLock& lock) { condition_.wait(lock); }
    void notify() { condition_.notify_one(); }
    Mutex mutex_;
    WaitCondition condition_;
};

class QThreaded {
public:
    typedef QMutex Mutex;
    typedef QMutexLocker ScopedLock;
    typedef QWaitCondition WaitCondition;
    void wait(ScopedLock&) { condition_.wait(mutex_); }
    void notify() { condition_.wakeOne(); }
    QThreaded():mutex_(new QMutex) {};
    ~QThreaded() { delete mutex_; }
    Mutex* mutex_;
    WaitCondition condition_;
};

class SingleThreaded {
public:
    typedef void* Mutex;
    typedef void* ScopedLock;
    void wait(ScopedLock&) {}
    void notify() {}
    Mutex mutex_;
};

template <class ThreadingPolicy>
class Foo {
public:
    typedef typename ThreadingPolicy::ScopedLock ScopedLock;

    void bar() {
        ScopedLock lock(tp.mutex_);
        cout << "Bar!" << endl;
    }
private:
    ThreadingPolicy tp;
};

template<typename Data, class ThreadingPolicy>
class concurrent_queue
{
public:
    void push(Data const& data)
    {
        {
            ScopedLock lock(tp.mutex_);
            the_queue.push(data);
        }
        tp.notify();
    }

    bool empty() const
    {
        ScopedLock lock(tp.mutex_);
        return the_queue.empty();
    }

    bool try_pop(Data& popped_value)
    {
        ScopedLock lock(tp.mutex_);
        if(the_queue.empty())
        {
            return false;
        }

        popped_value = the_queue.front();
        the_queue.pop();
        return true;
    }

    void wait_and_pop(Data& popped_value)
    {
        ScopedLock lock(tp.mutex_);
        while(the_queue.empty())
        {
            wait(mutex_);
        }

        popped_value=the_queue.front();
        the_queue.pop();
    }
private:
    typedef typename ThreadingPolicy::ScopedLock ScopedLock;
    std::queue<Data> the_queue;
    ThreadingPolicy tp;
};

int main(int, char **)
{
    Foo<BoostThreaded> my_threaded_foo;
    my_threaded_foo.bar();

    Foo<QThreaded> my_qthreaded_foo;
    my_qthreaded_foo.bar();

    Foo<SingleThreaded> my_singlethreaded_foo;
    my_singlethreaded_foo.bar();

    concurrent_queue<float, BoostThreaded> my_concurrent_float_queue;
    my_concurrent_float_queue.push(23.42f);

    float f;
    my_concurrent_float_queue.wait_and_pop(f);
    cout << f << endl;

    return 0;
}
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