added wxSemaphore (with docs), new version of wxCondition and bug fixes to wxThread (patch 538242 by K.S. Sreeram)
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@14907 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
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@@ -12,28 +12,22 @@ perfect because in this particular case it would be much better to just
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worker threads it already makes much more sense).
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Note that a call to \helpref{Signal()}{wxconditionsignal} may happen before the
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other thread calls \helpref{Wait()}{wxconditionwait} but, in marked contrast
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with the pthread conditions, this will still work as the missed signals are
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queued and \helpref{Wait()}{wxconditionwait} simply returns immediately if
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there are ny pending signals.
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However, the calls to \helpref{Broadcast()}{wxconditionbroadcast} are {\bf not}
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queued and so it will only wake up the threads already waiting on the
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condition. Accordingly, you will probably want to use a mutex to ensure that
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the thread(s) you want to be waken up have indeed started to wait before
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calling \helpref{Broadcast()}{wxconditionbroadcast}.
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other thread calls \helpref{Wait()}{wxconditionwait} and, just as with the
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pthread conditions, the signal is then lost and so if you want to be sure to
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get it you must use a mutex together with the condition variable.
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\wxheading{Example}
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This example shows how a main thread may launch a worker thread and wait until
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it starts running:
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This example shows how a main thread may launch a worker thread which starts
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running and then waits until the main thread signals it to continue:
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\begin{verbatim}
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class MyWaitingThread : public wxThread
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{
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public:
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MyWaitingThread(wxCondition *condition)
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MyWaitingThread(wxMutex *mutex, wxCondition *condition)
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{
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m_mutex = mutex;
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m_condition = condition;
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Create();
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@@ -41,8 +35,11 @@ public:
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virtual ExitCode Entry()
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{
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// let the main thread know that we started running
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// wait for the signal from the main thread: it is absolutely necessary
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// to look the mutex before doing it!
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m_mutex->Lock();
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m_condition->Signal();
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m_mutex->Unlock();
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... do our job ...
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@@ -55,15 +52,23 @@ private:
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int main()
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{
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wxCondition condition;
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MyWaitingThread *thread - new MyWaitingThread(&condition);
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wxMutex mutex;
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wxCondition condition(&mutex);
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thread->Run();
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for ( int i = 0; i < 10; i++ )
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{
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MyWaitingThread *thread = new MyWaitingThread(&mutex, &condition);
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// wait until the thread really starts running
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condition.Wait();
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thread->Run();
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}
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...
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// wake up one of the threads
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condition.Signal();
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// wake up all the other ones
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condition.Broadcast();
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... wait until they terminate or do something else ...
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return 0;
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}
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@@ -85,37 +90,57 @@ None.
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\membersection{wxCondition::wxCondition}\label{wxconditionconstr}
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\func{}{wxCondition}{\void}
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\func{}{wxCondition}{\param{wxMutex }{*mutex}}
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Default constructor.
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Default and only constructor. The {\it mutex} must be non {\tt NULL}.
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\membersection{wxCondition::\destruct{wxCondition}}
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\func{}{\destruct{wxCondition}}{\void}
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Destroys the wxCondition object.
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Destroys the wxCondition object. The destructor is not virtual so this class
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should not be used polymorphically.
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\membersection{wxCondition::Broadcast}\label{wxconditionbroadcast}
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\func{void}{Broadcast}{\void}
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Broadcasts to all waiting objects.
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Broadcasts to all waiting threads, waking all of them up. Note that this method
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may be called whether the mutex associated with this condition is locked or
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not.
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\wxheading{See also}
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\helpref{wxCondition::Signal}{wxconditionsignal}
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\membersection{wxCondition::Signal}\label{wxconditionsignal}
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\func{void}{Signal}{\void}
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Signals the object.
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Signals the object waking up at most one thread. If several threads are waiting
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on the same condition, the exact thread which is woken up is undefined. If no
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threads are waiting, the signal is lost and the condition would have to be
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signalled again to wake up any thread which may start waiting on it later.
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Note that this method may be called whether the mutex associated with this
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condition is locked or not.
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\wxheading{See also}
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\helpref{wxCondition::Broadcast}{wxconditionbroadcast}
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\membersection{wxCondition::Wait}\label{wxconditionwait}
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\func{void}{Wait}{\void}
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Waits indefinitely.
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Waits until the condition is signalled.
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\func{bool}{Wait}{\param{unsigned long}{ sec}, \param{unsigned long}{ nsec}}
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Waits until a signal is raised or the timeout has elapsed.
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Waits until the condition is signalled or the timeout has elapsed.
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Note that the mutex associated with this condition {\bf must} be acquired by
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the thread before calling this method.
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\wxheading{Parameters}
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@@ -125,5 +150,7 @@ Waits until a signal is raised or the timeout has elapsed.
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\wxheading{Return value}
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The second form returns if the signal was raised, or FALSE if there was a timeout.
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The second form returns {\tt TRUE} if the condition has been signalled, or
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{\tt FALSE} if it returned because the timeout has elapsed.
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