AsyncEngine.h
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1/*
2 * Copyright (C) 1996-2022 The Squid Software Foundation and contributors
3 *
4 * Squid software is distributed under GPLv2+ license and includes
5 * contributions from numerous individuals and organizations.
6 * Please see the COPYING and CONTRIBUTORS files for details.
7 */
8
9#ifndef SQUID_ASYNCENGINE_H
10#define SQUID_ASYNCENGINE_H
11
12/* Abstract interface for async engines which an event loop can utilise.
13 *
14 * Some implementations will be truly async, others like the event engine
15 * will be pseudo async.
16 */
17
19{
20
21public:
22 /* error codes returned from checkEvents. If the return value is not
23 * negative, then it is the requested delay until the next call. If it is
24 * negative, it is one of the following codes:
25 */
27 /* this engine is completely idle: it has no pending events, and nothing
28 * registered with it that can create events
29 */
31 /* some error has occurred in this engine */
32 EVENT_ERROR = -2
33 };
34
35 virtual ~AsyncEngine() {}
36
37 /* Check the engine for events. If there are events that have completed,
38 * the engine should at this point hand them off to their dispatcher.
39 * Engines that operate asynchronously - i.e. the DiskThreads engine -
40 * should hand events off to their dispatcher as they arrive rather than
41 * waiting for checkEvents to be called. Engines like poll and select should
42 * use this call as the time to perform their checks with the OS for new
43 * events.
44 *
45 * The return value is the status code of the event checking. If its a
46 * non-negative value then it is used as hint for the minimum requested
47 * time before checkEvents is called again. I.e. the event engine knows
48 * how long it is until the next event will be scheduled - so it will
49 * return that time (in milliseconds).
50 *
51 * The timeout value is a requested timeout for this engine - the engine
52 * should not block for more than this period. (If it takes longer than the
53 * timeout to do actual checks that's fine though undesirable).
54 */
55 virtual int checkEvents(int timeout) = 0;
56};
57
58#endif /* SQUID_ASYNCENGINE_H */
59
virtual int checkEvents(int timeout)=0
virtual ~AsyncEngine()
Definition: AsyncEngine.h:35

 

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