Glenn Maynard
afbd2f3bbc
in Linux. This can happen if the clock is turned back when using the system clock; the time will be less than ArchHooks_Unix::m_iStartTime.
93 lines
3.2 KiB
C++
93 lines
3.2 KiB
C++
#include "global.h"
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#include "ArchHooks.h"
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ArchHooks *HOOKS = NULL;
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#include "Selector_ArchHooks.h"
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ArchHooks *MakeArchHooks()
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{
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return new ARCH_HOOKS;
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}
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/*
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* This is a helper for GetMicrosecondsSinceStart on systems with a system
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* timer that may loop or move backwards.
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*
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* The time may decrease last for at least two reasons:
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*
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* 1. The underlying timer may be 32-bit and use millisecs internally, in which case
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* the timer will loop every 2^32 ms.
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*
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* 2. The underlying clock may have moved backwards (eg. system clock and ntpd).
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*
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* If the system clock moves backwards, we can't just clamp the time; if it moved back
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* an hour, we'd sit around for an hour until it catches up.
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*
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* Keep track of an offset: the amount of time to add to the result. If we move back
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* by 100ms, the offset will be increased by 100ms. If we loop, the offset will be
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* increased by the duration 2^32 ms.
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*
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* This helper only needs to be used if one or both of the above conditions can occur.
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* If the underlying timer is reliable, this doesn't need to be used (for a small
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* efficiency bonus). Also, you may omit this for GetMicrosecondsSinceStart() when
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* bAccurate == false.
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*/
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int64_t ArchHooks::FixupTimeIfLooped( int64_t usecs )
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{
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static int64_t last = 0;
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static int64_t offset_us = 0;
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/* The time has wrapped if the last time was very high and the current time is very low. */
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const int64_t i32BitMaxMs = uint64_t(1) << 32;
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const int64_t i32BitMaxUs = i32BitMaxMs*1000;
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const int64_t one_day = uint64_t(24*60*60)*1000000;
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if( last > (i32BitMaxUs-one_day) && usecs < one_day )
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offset_us += i32BitMaxUs;
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last = usecs;
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return usecs + offset_us;
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}
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int64_t ArchHooks::FixupTimeIfBackwards( int64_t usecs )
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{
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static int64_t last = 0;
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static int64_t offset_us = 0;
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if( usecs < last )
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{
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/* The time has moved backwards. Increase the offset by the amount we moved. */
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offset_us += last - usecs;
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}
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last = usecs;
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return usecs + offset_us;
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}
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/*
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* (c) 2003-2004 Glenn Maynard, Chris Danford
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* All rights reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, and/or sell copies of the Software, and to permit persons to
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* whom the Software is furnished to do so, provided that the above
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* copyright notice(s) and this permission notice appear in all copies of
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* the Software and that both the above copyright notice(s) and this
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* permission notice appear in supporting documentation.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF
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* THIRD PARTY RIGHTS. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR HOLDERS
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* INCLUDED IN THIS NOTICE BE LIABLE FOR ANY CLAIM, OR ANY SPECIAL INDIRECT
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* OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
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* OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
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* OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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* PERFORMANCE OF THIS SOFTWARE.
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*/
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