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	1	%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
	2	%% Name: semaphore.tex
	3	%% Purpose: wxSemaphore documentation
	4	%% Author: Vadim Zeitlin
	5	%% Modified by:
	6	%% Created: 02.04.02
	7	%% RCS-ID: $Id$
	8	%% Copyright: (c) 2002 Vadim Zeitlin
	9	%% License: wxWindows license
	10	%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
	11
	12	\section{\class{wxSemaphore}}\label{wxsemaphore}
	13
	14	wxSemaphore is a counter limiting the number of threads concurrently accessing
	15	a shared resource. This counter is always between $0$ and the maximum value
	16	specified during the semaphore creation. When the counter is strictly greater
	17	than $0$, a call to \helpref{Wait}{wxsemaphorewait} returns immediately and
	18	decrements the counter. As soon as it reaches $0$, any subsequent calls to
	19	\helpref{Wait}{wxsemaphorewait} block and only return when the semaphore
	20	counter becomes strictly positive again as the result of calling
	21	\helpref{Post}{wxsemaphorepost} which increments the counter.
	22
	23	In general, the semaphores are useful to restrict access to a shared resource
	24	which can only be accessed by some fixed number of clients at once. For
	25	example, when modeling a hotel reservation system a semaphore with the counter
	26	equal to the total number of available rooms could be created. Each time a room
	27	is reserved, the semaphore should be acquired by calling
	28	\helpref{Wait}{wxsemaphorewait} and each time a room is freed it should be
	29	released by calling \helpref{Post}{wxsemaphorepost}.
	30
	31	\wxheading{Derived from}
	32
	33	No base class
	34
	35	\wxheading{Include files}
	36
	37	<wx/thread.h>
	38
	39	\latexignore{\rtfignore{\wxheading{Members}}}
	40
	41	\membersection{wxSemaphore::wxSemaphore}\label{wxsemaphorewxsemaphore}
	42
	43	\func{}{wxSemaphore}{\param{int }{initialcount = 0}, \param{int }{maxcount = 0}}
	44
	45	Specifying a {\it maxcount} of $0$ actually makes wxSemaphore behave as if
	46	there is no upper limit. If maxcount is $1$ the semaphore behaves exactly as a
	47	mutex.
	48
	49	{\it initialcount} is the initial value of the semaphore which must be between
	50	$0$ and {\it maxcount} (if it is not set to $0$).
	51
	52	\membersection{wxSemaphore::\destruct{wxSemaphore}}\label{wxsemaphoredtor}
	53
	54	\func{}{\destruct{wxSemaphore}}{\void}
	55
	56	Destructor is not virtual, don't use this class polymorphically.
	57
	58	\membersection{wxSemaphore::Post}\label{wxsemaphorepost}
	59
	60	\func{void}{Post}{\void}
	61
	62	Increments the semaphore count and signals one of the waiting threads in an
	63	atomic way.
	64
	65	\membersection{wxSemaphore::TryWait}\label{wxsemaphoretrywait}
	66
	67	\func{bool}{TryWait}{\void}
	68
	69	Same as \helpref{Wait()}{wxsemaphorewait}, but does not block, returns
	70	{\tt TRUE} if the semaphore was successfully acquired and {\tt FALSE} if the
	71	count is zero and it couldn't be done.
	72
	73	\membersection{wxSemaphore::Wait}\label{wxsemaphorewait}
	74
	75	\func{void}{Wait}{\void}
	76
	77	Wait indefinitely until the semaphore count becomes strictly positive
	78	and then decrement it and return.
	79
	80	\func{bool}{Wait}{\param{unsigned long }{timeout\_millis}}
	81
	82	Same as the version above, but with a timeout limit: returns {\tt TRUE} if the
	83	semaphore was acquired and {\tt FALSE} if the timeout has elapsed
	84