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SharedQueue.st
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SharedQueue.st
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"======================================================================
|
| SharedQueue Method Definitions
|
|
======================================================================"
"======================================================================
|
| Copyright 1988,92,94,95,99,2000,2001,2002
| Free Software Foundation, Inc.
| Written by Steve Byrne.
|
| This file is part of the GNU Smalltalk class library.
|
| The GNU Smalltalk class library is free software; you can redistribute it
| and/or modify it under the terms of the GNU Lesser General Public License
| as published by the Free Software Foundation; either version 2.1, or (at
| your option) any later version.
|
| The GNU Smalltalk class library 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 Lesser
| General Public License for more details.
|
| You should have received a copy of the GNU Lesser General Public License
| along with the GNU Smalltalk class library; see the file COPYING.LIB.
| If not, write to the Free Software Foundation, 59 Temple Place - Suite
| 330, Boston, MA 02110-1301, USA.
|
======================================================================"
Object subclass: SharedQueue [
| queueSem valueReady queue |
<category: 'Language-Processes'>
<comment: 'My instances provide a guaranteed safe mechanism to allow for communication
between processes. All access to the underlying data structures is
controlled with critical sections so that things proceed smoothly.'>
SharedQueue class >> new [
"Create a new instance of the receiver"
<category: 'instance creation'>
^self basicNew init: (OrderedCollection new: 10)
]
SharedQueue class >> sortBlock: sortBlock [
"Create a new instance of the receiver which implements a
priority queue with the given sort block"
<category: 'instance creation'>
^self basicNew init: (SortedCollection sortBlock: sortBlock)
]
isEmpty [
"Answer whether there is an object on the queue"
<category: 'accessing'>
^queue isEmpty
]
next [
"Wait for an object to be on the queue, then remove it and answer it"
<category: 'accessing'>
| result |
valueReady wait.
queueSem critical: [result := queue removeFirst].
^result
]
nextPut: value [
"Put value on the queue and answer it"
<category: 'accessing'>
queueSem critical: [queue add: value].
valueReady signal.
^value
]
peek [
"Wait for an object to be on the queue if necessary, then answer the
same object that #next would answer without removing it."
<category: 'accessing'>
| result |
valueReady wait.
queueSem critical: [result := queue first].
valueReady signal.
^result
]
init: aCollection [
<category: 'private'>
queue := aCollection.
valueReady := Semaphore new.
queueSem := Semaphore forMutualExclusion
]
]