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Diffstat (limited to 'indra/llcommon/lldeadmantimer.h')
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diff --git a/indra/llcommon/lldeadmantimer.h b/indra/llcommon/lldeadmantimer.h new file mode 100644 index 0000000000..84023723ab --- /dev/null +++ b/indra/llcommon/lldeadmantimer.h @@ -0,0 +1,171 @@ +/** +* @file lldeadmantimer.h +* @brief Interface to a simple event timer with a deadman's switch +* @author monty@lindenlab.com +* +* $LicenseInfo:firstyear=2013&license=viewerlgpl$ +* Second Life Viewer Source Code +* Copyright (C) 2013, Linden Research, Inc. +* +* This library is free software; you can redistribute it and/or +* modify it under the terms of the GNU Lesser General Public +* License as published by the Free Software Foundation; +* version 2.1 of the License only. +* +* This library 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 +* Lesser General Public License for more details. +* +* You should have received a copy of the GNU Lesser General Public +* License along with this library; if not, write to the Free Software +* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA +* +* Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA +* $/LicenseInfo$ +*/ + +#ifndef LL_DEADMANTIMER_H +#define LL_DEADMANTIMER_H + + +#include "linden_common.h" + +#include "lltimer.h" + + +/// @file lldeadmantimer.h +/// +/// There are interesting user-experienced events in the viewer that +/// would seem to have well-defined start and stop points but which +/// actually lack such milestones in the code. Such events (like +/// time to load meshes after logging in, initial inventory load, +/// display name fetch) can be defined somewhat after-the-fact by +/// noticing when we no longer perform operations towards their +/// completion. This class is intended to help in such applications. +/// +/// What it implements is a deadman's switch (also known as a +/// keepalive switch and a doorbell switch). The basic operation is +/// as follows: +/// +/// * LLDeadmanTimer is instantiated with a horizon value in seconds, +/// one for each event of interest. +/// * When an event starts, @see start() is invoked to begin a +/// timing operation. +/// * As operations are performed in service of the event (issuing +/// HTTP requests, receiving responses), @see ringBell() is invoked +/// to inform the timer that the operation is still active. +/// * If the operation is canceled or otherwise terminated, @see +/// stop() can be called to end the timing operation. +/// * Concurrent with the ringBell() calls, the program makes +/// periodic (shorter than the horizon but not too short) calls +/// to @see isExpired() to see if the event has expired due to +/// either a stop() call or lack of activity (defined as a ringBell() +/// call in the previous 'horizon' seconds). If it has expired, +/// the caller also receives start, stop and count values for the +/// event which the application can then report in whatever manner +/// it sees fit. +/// * The timer becomes passive after an isExpired() call that returns +/// true. It can then be restarted with a new start() call. +/// +/// Threading: Instances are not thread-safe. They also use +/// timing code from lltimer.h which is also unsafe. +/// +/// Allocation: Not refcounted, may be stack or heap allocated. +/// + +class LL_COMMON_API LLDeadmanTimer +{ +public: + /// Construct and initialize an LLDeadmanTimer + /// + /// @param horizon Time, in seconds, after the last @see ringBell() + /// call at which point the timer will consider itself + /// expired. + /// + LLDeadmanTimer(F64 horizon); + + ~LLDeadmanTimer() + {} + +private: + LLDeadmanTimer(const LLDeadmanTimer &); // Not defined + void operator=(const LLDeadmanTimer &); // Not defined + +public: + /// Begin timing. If the timer is already active, it is reset + /// and timing begins now. + /// + /// @param now Current time as returned by @see + /// LLTimer::getCurrentClockCount(). If zero, + /// method will lookup current time. + /// + void start(U64 now = U64L(0)); + + + /// End timing. Actively declare the end of the event independent + /// of the deadman's switch operation. @see isExpired() will return + /// true and appropriate values will be returned. + /// + /// @param now Current time as returned by @see + /// LLTimer::getCurrentClockCount(). If zero, + /// method will lookup current time. + /// + void stop(U64 now = U64L(0)); + + + /// Declare that something interesting happened. This has two + /// effects on an unexpired-timer. 1) The expiration time + /// is extended for 'horizon' seconds after the 'now' value. + /// 2) An internal counter associated with the event is incremented. + /// This count is returned via the @see isExpired() method. + /// + /// @param now Current time as returned by @see + /// LLTimer::getCurrentClockCount(). If zero, + /// method will lookup current time. + /// + void ringBell(U64 now = U64L(0)); + + + /// Checks on the status of the timer Declare that something interesting happened. This has two + /// effects on an unexpired-timer. 1) The expiration time + /// is extended for 'horizon' seconds after the 'now' value. + /// 2) An internal counter associated with the event is incremented. + /// This count is returned via the @see isExpired() method. + /// + /// @param started If expired, the starting time of the event is + /// returned to the caller via this reference. + /// + /// @param stopped If expired, the ending time of the event is + /// returned to the caller via this reference. + /// Ending time will be that provided in the + /// stop() method or the last ringBell() call + /// leading to expiration, whichever (stop() call + /// or notice of expiration) happened first. + /// + /// @param count If expired, the number of ringBell() calls + /// made prior to expiration. + /// + /// @param now Current time as returned by @see + /// LLTimer::getCurrentClockCount(). If zero, + /// method will lookup current time. + /// + /// @return true if the timer has expired, false otherwise. + /// If true, it also returns the started, + /// stopped and count values otherwise these are + /// left unchanged. + /// + bool isExpired(F64 & started, F64 & stopped, U64 & count, U64 now = U64L(0)); + +protected: + U64 mHorizon; + bool mActive; + bool mDone; + U64 mStarted; + U64 mExpires; + U64 mStopped; + U64 mCount; +}; + + +#endif // LL_DEADMANTIMER_H |