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Diffstat (limited to 'indra/llcommon/lleventfilter.h')
| -rw-r--r-- | indra/llcommon/lleventfilter.h | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/indra/llcommon/lleventfilter.h b/indra/llcommon/lleventfilter.h new file mode 100644 index 0000000000..89f0c7ea43 --- /dev/null +++ b/indra/llcommon/lleventfilter.h @@ -0,0 +1,186 @@ +/** + * @file lleventfilter.h + * @author Nat Goodspeed + * @date 2009-03-05 + * @brief Define LLEventFilter: LLEventStream subclass with conditions + * + * $LicenseInfo:firstyear=2009&license=viewergpl$ + * Copyright (c) 2009, Linden Research, Inc. + * $/LicenseInfo$ + */ + +#if ! defined(LL_LLEVENTFILTER_H) +#define LL_LLEVENTFILTER_H + +#include "llevents.h" +#include "stdtypes.h" +#include "lltimer.h" +#include <boost/function.hpp> + +/** + * Generic base class + */ +class LL_COMMON_API LLEventFilter: public LLEventStream +{ +public: + /// construct a standalone LLEventFilter + LLEventFilter(const std::string& name="filter", bool tweak=true): + LLEventStream(name, tweak) + {} + /// construct LLEventFilter and connect it to the specified LLEventPump + LLEventFilter(LLEventPump& source, const std::string& name="filter", bool tweak=true); + + /// Post an event to all listeners + virtual bool post(const LLSD& event) = 0; +}; + +/** + * Pass through only events matching a specified pattern + */ +class LLEventMatching: public LLEventFilter +{ +public: + /// Pass an LLSD map with keys and values the incoming event must match + LLEventMatching(const LLSD& pattern); + /// instantiate and connect + LLEventMatching(LLEventPump& source, const LLSD& pattern); + + /// Only pass through events matching the pattern + virtual bool post(const LLSD& event); + +private: + LLSD mPattern; +}; + +/** + * Wait for an event to be posted. If no such event arrives within a specified + * time, take a specified action. See LLEventTimeout for production + * implementation. + * + * @NOTE This is an abstract base class so that, for testing, we can use an + * alternate "timer" that doesn't actually consume real time. + */ +class LL_COMMON_API LLEventTimeoutBase: public LLEventFilter +{ +public: + /// construct standalone + LLEventTimeoutBase(); + /// construct and connect + LLEventTimeoutBase(LLEventPump& source); + + /// Callable, can be constructed with boost::bind() + typedef boost::function<void()> Action; + + /** + * Start countdown timer for the specified number of @a seconds. Forward + * all events. If any event arrives before timer expires, cancel timer. If + * no event arrives before timer expires, take specified @a action. + * + * This is a one-shot timer. Once it has either expired or been canceled, + * it is inert until another call to actionAfter(). + * + * Calling actionAfter() while an existing timer is running cheaply + * replaces that original timer. Thus, a valid use case is to detect + * idleness of some event source by calling actionAfter() on each new + * event. A rapid sequence of events will keep the timer from expiring; + * the first gap in events longer than the specified timer will fire the + * specified Action. + * + * Any post() call cancels the timer. To be satisfied with only a + * particular event, chain on an LLEventMatching that only passes such + * events: + * + * @code + * event ultimate + * source ---> LLEventMatching ---> LLEventTimeout ---> listener + * @endcode + * + * @NOTE + * The implementation relies on frequent events on the LLEventPump named + * "mainloop". + */ + void actionAfter(F32 seconds, const Action& action); + + /** + * Like actionAfter(), but where the desired Action is LL_ERRS + * termination. Pass the timeout time and the desired LL_ERRS @a message. + * + * This method is useful when, for instance, some async API guarantees an + * event, whether success or failure, within a stated time window. + * Instantiate an LLEventTimeout listening to that API and call + * errorAfter() on each async request with a timeout comfortably longer + * than the API's time guarantee (much longer than the anticipated + * "mainloop" granularity). + * + * Then if the async API breaks its promise, the program terminates with + * the specified LL_ERRS @a message. The client of the async API can + * therefore assume the guarantee is upheld. + * + * @NOTE + * errorAfter() is implemented in terms of actionAfter(), so all remarks + * about calling actionAfter() also apply to errorAfter(). + */ + void errorAfter(F32 seconds, const std::string& message); + + /** + * Like actionAfter(), but where the desired Action is a particular event + * for all listeners. Pass the timeout time and the desired @a event data. + * + * Suppose the timeout should only be satisfied by a particular event, but + * the ultimate listener must see all other incoming events as well, plus + * the timeout @a event if any: + * + * @code + * some LLEventMatching LLEventMatching + * event ---> for particular ---> LLEventTimeout ---> for timeout + * source event event \ + * \ \ ultimate + * `-----------------------------------------------------> listener + * @endcode + * + * Since a given listener can listen on more than one LLEventPump, we can + * set things up so it sees the set union of events from LLEventTimeout + * and the original event source. However, as LLEventTimeout passes + * through all incoming events, the "particular event" that satisfies the + * left LLEventMatching would reach the ultimate listener twice. So we add + * an LLEventMatching that only passes timeout events. + * + * @NOTE + * eventAfter() is implemented in terms of actionAfter(), so all remarks + * about calling actionAfter() also apply to eventAfter(). + */ + void eventAfter(F32 seconds, const LLSD& event); + + /// Pass event through, canceling the countdown timer + virtual bool post(const LLSD& event); + + /// Cancel timer without event + void cancel(); + +protected: + virtual void setCountdown(F32 seconds) = 0; + virtual bool countdownElapsed() const = 0; + +private: + bool tick(const LLSD&); + + LLBoundListener mMainloop; + Action mAction; +}; + +/// Production implementation of LLEventTimoutBase +class LL_COMMON_API LLEventTimeout: public LLEventTimeoutBase +{ +public: + LLEventTimeout(); + LLEventTimeout(LLEventPump& source); + +protected: + virtual void setCountdown(F32 seconds); + virtual bool countdownElapsed() const; + +private: + LLTimer mTimer; +}; + +#endif /* ! defined(LL_LLEVENTFILTER_H) */ |