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Aminet - June 1993 [Walnut Creek].iso
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gnu_smalltalk1_2.lha
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Semaphore.st
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1992-02-15
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2KB
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89 lines
"======================================================================
|
| Semaphore Method Definitions
|
======================================================================"
"======================================================================
|
| Copyright (C) 1990, 1991, 1992 Free Software Foundation, Inc.
| Written by Steve Byrne.
|
| This file is part of GNU Smalltalk.
|
| GNU Smalltalk is free software; you can redistribute it and/or modify it
| under the terms of the GNU General Public License as published by the Free
| Software Foundation; either version 1, or (at your option) any later version.
|
| GNU Smalltalk is distributed in the hope that it will be useful, but WITHOUT
| ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
| FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
| details.
|
| You should have received a copy of the GNU General Public License along with
| GNU Smalltalk; see the file COPYING. If not, write to the Free Software
| Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
|
======================================================================"
"
| Change Log
| ============================================================================
| Author Date Change
| sbb 16 Mar 91 Class creation now separate statement.
|
| sbyrne 19 Sep 89 Converted to use real method categories.
|
| sbyrne 25 Apr 89 created.
|
"
LinkedList subclass: #Semaphore
instanceVariableNames: 'signals'
classVariableNames: ''
poolDictionaries: ''
category: nil
!
Semaphore comment:
'My instances represent counting semaphores. I provide methods for signalling
the semaphore''s availability, and methods for waiting for its availability.
I also provide some methods for implementing critical sections. I currently
do not (because the underlying system does not) support asynchronous
signals, such as might be generated by C signals.' !
!Semaphore class methodsFor: 'instance creation'!
new
^self basicNew initSemaphore
!
forMutualExclusion
| sem |
sem _ self new.
sem signal.
^sem
!!
!Semaphore methodsFor: 'mutual exclusion'!
critical: aBlock
| result |
self wait.
result _ aBlock value.
self signal.
^result
!!
!Semaphore methodsFor: 'private'!
initSemaphore
signals _ 0
!!