54946cc95b
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@14965 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
85 lines
3.1 KiB
TeX
85 lines
3.1 KiB
TeX
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%% Name: semaphore.tex
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%% Purpose: wxSemaphore documentation
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%% Author: Vadim Zeitlin
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%% Modified by:
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%% Created: 02.04.02
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%% RCS-ID: $Id$
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%% Copyright: (c) 2002 Vadim Zeitlin
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%% License: wxWindows license
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\section{\class{wxSemaphore}}\label{wxsemaphore}
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wxSemaphore is a counter limiting the number of threads concurrently accessing
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a shared resource. This counter is always between $0$ and the maximum value
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specified during the semaphore creation. When the counter is strictly greater
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than $0$, a call to \helpref{Wait}{wxsemaphorewait} returns immediately and
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decrements the counter. As soon as it reaches $0$, any subsequent calls to
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\helpref{Wait}{wxsemaphorewait} block and only return when the semaphore
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counter becomes strictly positive again as the result of calling
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\helpref{Post}{wxsemaphorepost} which increments the counter.
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In general, the semaphores are useful to restict access to a shared resource
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which can only be accessed by some fixed number of clients at once. For
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example, when modeling a hotel reservation system a semaphore with the counter
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equal to the total number of available rooms could be created. Each time a room
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is reserved, the semaphore should be acquired by calling
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\helpref{Wait}{wxsemaphorewait} and each time a room is freed it should be
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released by calling \helpref{Post}{wxsemaphorepost}.
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\wxheading{Derived from}
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No base class
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\wxheading{Include files}
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<wx/thread.h>
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\latexignore{\rtfignore{\wxheading{Members}}}
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\membersection{wxSemaphore::wxSemaphore}\label{wxsemaphorewxsemaphore}
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\func{}{wxSemaphore}{\param{int }{initialcount = 0}, \param{int }{maxcount = 0}}
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Specifying a {\it maxcount} of $0$ actually makes wxSemaphore behave as if
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there is no upper limit. If maxcount is $1$ the semaphore behaves exactly as a
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mutex.
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{\it initialcount} is the initial value of the semaphore which must be between
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$0$ and {\it maxcount} (if it is not set to $0$).
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\membersection{wxSemaphore::\destruct{wxSemaphore}}\label{wxsemaphoredtor}
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\func{}{\destruct{wxSemaphore}}{\void}
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Destructor is not virtual, don't use this class polymorphically.
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\membersection{wxSemaphore::Post}\label{wxsemaphorepost}
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\func{void}{Post}{\void}
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Increments the semaphore count and signals one of the waiting threads in an
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atomic way.
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\membersection{wxSemaphore::TryWait}\label{wxsemaphoretrywait}
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\func{bool}{TryWait}{\void}
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Same as \helpref{Wait()}{wxsemaphorewait}, but does not block, returns
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{\tt TRUE} if the semaphore was successfully acquired and {\tt FALSE} if the
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count is zero and it couldn't be done.
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\membersection{wxSemaphore::Wait}\label{wxsemaphorewait}
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\func{void}{Wait}{\void}
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Wait indefinitely until the semaphore count becomes strictly positive
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and then decrement it and return.
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\func{bool}{Wait}{\param{unsigned long }{timeout\_millis}}
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Same as the version above, but with a timeout limit: returns {\tt TRUE} if the
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semaphore was acquired and {\tt FALSE} if the timeout has ellapsed
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