tgt.cpp

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/* Copyright (c) 2010 Wildfire Games
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/*
 * Timer implementation using timeGetTime
 */

// note: WinMM is delay-loaded to avoid dragging it in when this timer
// implementation isn't used. (this is relevant because its startup is
// fairly slow)

#include "precompiled.h"
#include "lib/sysdep/os/win/whrt/tgt.h"

#include "lib/sysdep/os/win/whrt/counter.h"

#include "lib/sysdep/os/win/win.h"
#include <mmsystem.h>

#if MSC_VERSION
#pragma comment(lib, "winmm.lib")
#endif


// "Guidelines For Providing Multimedia Timer Support" claims that
// speeding the timer up to 2 ms has little impact, while 1 ms
// causes significant slowdown.
static const UINT PERIOD_MS = 2;

class CounterTGT : public ICounter
{
public:
    virtual const wchar_t* Name() const
    {
        return L"TGT";
    }

    Status Activate()
    {
        // note: timeGetTime is always available and cannot fail.

        MMRESULT ret = timeBeginPeriod(PERIOD_MS);
        ENSURE(ret == TIMERR_NOERROR);

        return INFO::OK;
    }

    void Shutdown()
    {
        timeEndPeriod(PERIOD_MS);
    }

    bool IsSafe() const
    {
        // the only point of criticism is the possibility of falling behind
        // due to lost interrupts. this can happen to any interrupt-based timer
        // and some systems may lack a counter-based timer, so consider TGT
        // 'safe'. note that it is still only chosen when all other timers fail.
        return true;
    }

    u64 Counter() const
    {
        return timeGetTime();
    }

    size_t CounterBits() const
    {
        return 32;
    }

    double NominalFrequency() const
    {
        return 1000.0;
    }

    double Resolution() const
    {
        return PERIOD_MS*1e-3;
    }
};

ICounter* CreateCounterTGT(void* address, size_t size)
{
    ENSURE(sizeof(CounterTGT) <= size);
    return new(address) CounterTGT();
}