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91 lines
3.2 KiB
C
91 lines
3.2 KiB
C
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/* -*- C++ -*-
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This file declares the QueuePolicy class.
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$ Author: Mirko Boehm $
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$ Copyright: (C) 2004, 2005, 2006 Mirko Boehm $
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$ Contact: mirko@kde.org
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http://www.kde.org
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http://www.hackerbuero.org $
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public License
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along with this library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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Boston, MA 02110-1301, USA.
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$Id: DebuggingAids.h 30 2005-08-16 16:16:04Z mirko $
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*/
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#ifndef QUEUEPOLICY_H
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#define QUEUEPOLICY_H
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#include <threadweaver/threadweaver_export.h>
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namespace ThreadWeaver {
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class Job;
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/** QueuePolicy is an interface for customizations of the queueing behaviour
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of sets of jobs.
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A job can have a queueing policy assigned. In that case, the job is only
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executed when the method canRun() of the assigned policy returns true. For
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every call to canRun() that returns true, it is guaranteed that the method
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free() or the method release() is called. Calling free() means the job has
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been executed, while calling release() means the job was not executed for
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external reasons, and will be retried later on.
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As an example, dependencies can be implemented using a QueuePolicy:
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canRun() returns true when the job has no unresolved dependencies. free()
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and release() are empty.
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A job can have multiple queue policies assigned, and will only be executed
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if all of them return true from canRun() within the same execution attempt.
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Jobs only keep a reference to the QueuePolicy. Therefore, the same object
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can be assigned to multiple jobs and this way control the way all those
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jobs are executed. Jobs never assume ownership of their assigned queue
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policies.
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*/
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class THREADWEAVER_EXPORT QueuePolicy
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{
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public:
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virtual ~QueuePolicy() {}
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/** canRun() is called before the job is executed.
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The job will only be executed if canRun() returns true.
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*/
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virtual bool canRun( Job* ) = 0;
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/** free() is called after the job has been executed.
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It is guaranteed that free is called only after canRun()
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returned true at an earlier time.
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*/
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virtual void free( Job* ) = 0;
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/** release() is called if canRun() returned true, but the job has not
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been executed for external reasons. For example, a second
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QueuePolicy could have returned false from canRun() for the same
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job.
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*/
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virtual void release( Job* ) = 0;
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/** destructing() is called when a Job that has this queue policy
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assigned gets destructed.
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*/
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virtual void destructed ( Job* ) = 0;
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};
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}
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#endif
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