Mutex documentation from Moshe.

Doc/lib/libmutex.tex

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+% LaTeXed from comments in file
+\section{\module{mutex} ---
+         Mutual exclusion support}
+
+\declaremodule{standard}{mutex}
+\sectionauthor{Moshe Zadka}{mzadka@geocities.com}
+\modulesynopsis{Lock and queue for mutual exclusion.}
+
+The \module{mutex} defines a class that allows mutual-exclusion
+via aquiring and releasing locks. It does not require (or imply)
+and threading or multi-tasking, though it could be useful for
+those purposes.
+
+The \module{mutex} module defines the following class:
+
+\begin{classdesc}{mutex}{}
+Create a new (unlocked) mutex.
+
+A mutex has two pieces of state --- a ``locked'' bit and a queue.
+When the mutex is not locked, the queue is empty.
+Otherwise, the queue contains 0 or more 
+\code{(\var{function}, \var{argument})} pairs
+representing functions (or methods) waiting to acquire the lock.
+When the mutex is unlocked while the queue is not empty,
+the first queue entry is removed and its 
+\code{\var{function}(\var{argument})} pair called,
+implying it now has the lock.
+
+Of course, no multi-threading is implied -- hence the funny interface
+for lock, where a function is called once the lock is aquired.
+\end{classdesc}
+
+
+\subsection{Mutex Objects \label{mutex-objects}}
+
+\class{mutex} objects have following methods:
+
+\begin{methoddesc}{test}{}
+Check whether the mutex is locked.
+\end{methoddesc}
+
+\begin{methoddesc}{testandset}{}
+``Atomic'' test-and-set, grab the lock if it is not set,
+and return true, otherwise, return false.
+\end{methoddesc}
+
+\begin{methoddesc}{lock}{function, argument}
+Execute \code{\var{function}(\var{argument})}, unless the mutex is locked.
+In the case it is locked, place the function and argument on the queue.
+See \method{unlock} for explanation of when
+\code{\var{function}(\var{argument})} is executed in that case.
+\end{methoddesc}
+
+\begin{methoddesc}{unlock}{}
+Unlock the mutex if queue is empty, otherwise execute the first element
+in the queue.
+\end{methoddesc}