forked from mirrors/0ad
janwas
c3a42633fa
also improved filtering of the frame delta times. while at it, improved interface of whrt backends to avoid leaking implementation details. This was SVN commit r6401.
91 lines
1.9 KiB
C++
91 lines
1.9 KiB
C++
/**
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* =========================================================================
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* File : tgt.cpp
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* Project : 0 A.D.
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* Description : Timer implementation using timeGetTime
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* =========================================================================
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*/
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// license: GPL; see lib/license.txt
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// note: WinMM is delay-loaded to avoid dragging it in when this timer
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// implementation isn't used. (this is relevant because its startup is
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// fairly slow)
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#include "precompiled.h"
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#include "tgt.h"
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#include "counter.h"
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#include "lib/sysdep/os/win/win.h"
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#include <mmsystem.h>
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#if MSC_VERSION
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#pragma comment(lib, "winmm.lib")
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#endif
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// "Guidelines For Providing Multimedia Timer Support" claims that
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// speeding the timer up to 2 ms has little impact, while 1 ms
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// causes significant slowdown.
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static const UINT PERIOD_MS = 2;
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class CounterTGT : public ICounter
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{
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public:
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virtual const char* Name() const
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{
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return "TGT";
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}
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LibError Activate()
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{
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// note: timeGetTime is always available and cannot fail.
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MMRESULT ret = timeBeginPeriod(PERIOD_MS);
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debug_assert(ret == TIMERR_NOERROR);
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return INFO::OK;
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}
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void Shutdown()
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{
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timeEndPeriod(PERIOD_MS);
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}
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bool IsSafe() const
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{
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// the only point of criticism is the possibility of falling behind
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// due to lost interrupts. this can happen to any interrupt-based timer
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// and some systems may lack a counter-based timer, so consider TGT
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// 'safe'. note that it is still only chosen when all other timers fail.
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return true;
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}
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u64 Counter() const
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{
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return timeGetTime();
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}
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size_t CounterBits() const
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{
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return 32;
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}
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double NominalFrequency() const
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{
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return 1000.0;
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}
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double Resolution() const
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{
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return PERIOD_MS*1e-3;
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}
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};
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ICounter* CreateCounterTGT(void* address, size_t size)
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{
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debug_assert(sizeof(CounterTGT) <= size);
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return new(address) CounterTGT();
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}
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