AsyncEngine.h
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1 /*
2  * Copyright (C) 1996-2017 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 truely async, others like the event engine
15  * will be pseudo async.
16  */
17 
19 {
20 
21 public:
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  */
26  enum CheckError {
27  /* this engine is completely idle: it has no pending events, and nothing
28  * registered with it that can create events
29  */
30  EVENT_IDLE = -1,
31  /* some error has occured in this engine */
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 thats 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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