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/*
* $Id$
*
*
* SQUID Web Proxy Cache http://www.squid-cache.org/
* ----------------------------------------------------------
*
* Squid is the result of efforts by numerous individuals from
* the Internet community; see the CONTRIBUTORS file for full
* details. Many organizations have provided support for Squid's
* development; see the SPONSORS file for full details. Squid is
* Copyrighted (C) 2001 by the Regents of the University of
* California; see the COPYRIGHT file for full details. Squid
* incorporates software developed and/or copyrighted by other
* sources; see the CREDITS file for full details.
*
* This program 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 2 of the License, or
* (at your option) any later version.
*
* This program 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 this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
*
*/
#ifndef SQUID_ASYNCENGINE_H
#define SQUID_ASYNCENGINE_H
#include "squid.h"
/* Abstract interface for async engines which an event loop can utilise.
*
* Some implementations will be truely async, others like the event engine
* will be pseudo async.
*/
class AsyncEngine
{
public:
/* error codes returned from checkEvents. If the return value is not
* negative, then it is the requested delay until the next call. If it is
* negative, it is one of the following codes:
*/
enum CheckError {
/* this engine is completely idle: it has no pending events, and nothing
* registered with it that can create events
*/
EVENT_IDLE = -1,
/* some error has occured in this engine */
EVENT_ERROR = -2
};
virtual ~AsyncEngine() {}
/* Check the engine for events. If there are events that have completed,
* the engine should at this point hand them off to their dispatcher.
* Engines that operate asynchronously - i.e. the DiskThreads engine -
* should hand events off to their dispatcher as they arrive rather than
* waiting for checkEvents to be called. Engines like poll and select should
* use this call as the time to perform their checks with the OS for new
* events.
*
* The return value is the status code of the event checking. If its a
* non-negative value then it is used as hint for the minimum requested
* time before checkEvents is called again. I.e. the event engine knows
* how long it is until the next event will be scheduled - so it will
* return that time (in milliseconds).
*
* The timeout value is a requested timeout for this engine - the engine
* should not block for more than this period. (If it takes longer than the
* timeout to do actual checks thats fine though undesirable).
*/
virtual int checkEvents(int timeout) = 0;
};
#endif /* SQUID_ASYNCENGINE_H */
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