windows

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Author : Ryan C. Gordon
Date : 2021-10-23 15:00:31
Hash : 99c9727d
Message : timer: Added SDL_GetTicks64(), for a timer that doesn't wrap every ~49 days. Note that this removes the timeGetTime() fallback on Windows; it is a 32-bit counter and SDL2 should never choose to use it, as it only is needed if QueryPerformanceCounter() isn't available, and QPC is _always_ available on Windows XP and later. OS/2 has a similar situation, but since it isn't clear to me that similar promises can be made about DosTmrQueryTime() even in modern times, I decided to leave the fallback in, with some heroic measures added to try to provide a true 64-bit tick counter despite the 49-day wraparound. That approach can migrate to Windows too, if we discover some truly broken install that doesn't have QPC and still depends on timeGetTime(). Fixes #4870.

SDL_systimer.c

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2021 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/
#include "../../SDL_internal.h"

#ifdef SDL_TIMER_WINDOWS

#include "../../core/windows/SDL_windows.h"
#include <mmsystem.h>

#include "SDL_timer.h"
#include "SDL_hints.h"


/* The first (low-resolution) ticks value of the application */
static DWORD start = 0;
static BOOL ticks_started = FALSE; 

/* The first high-resolution ticks value of the application */
static LARGE_INTEGER start_ticks;
/* The number of ticks per second of the high-resolution performance counter */
static LARGE_INTEGER ticks_per_second;

static void
SDL_SetSystemTimerResolution(const UINT uPeriod)
{
#ifndef __WINRT__
    static UINT timer_period = 0;

    if (uPeriod != timer_period) {
        if (timer_period) {
            timeEndPeriod(timer_period);
        }

        timer_period = uPeriod;

        if (timer_period) {
            timeBeginPeriod(timer_period);
        }
    }
#endif
}

static void SDLCALL
SDL_TimerResolutionChanged(void *userdata, const char *name, const char *oldValue, const char *hint)
{
    UINT uPeriod;

    /* Unless the hint says otherwise, let's have good sleep precision */
    if (hint && *hint) {
        uPeriod = SDL_atoi(hint);
    } else {
        uPeriod = 1;
    }
    if (uPeriod || oldValue != hint) {
        SDL_SetSystemTimerResolution(uPeriod);
    }
}

void
SDL_TicksInit(void)
{
    BOOL rc;

    if (ticks_started) {
        return;
    }
    ticks_started = SDL_TRUE;

    /* if we didn't set a precision, set it high. This affects lots of things
       on Windows besides the SDL timers, like audio callbacks, etc. */
    SDL_AddHintCallback(SDL_HINT_TIMER_RESOLUTION,
                        SDL_TimerResolutionChanged, NULL);

    /* Set first ticks value */
    /* QueryPerformanceCounter allegedly is always available and reliable as of WinXP,
       so we'll rely on it here.
     */
    rc = QueryPerformanceFrequency(&ticks_per_second);
    SDL_assert(rc != 0);  /* this should _never_ fail if you're on XP or later. */
    QueryPerformanceCounter(&start_ticks);
}

void
SDL_TicksQuit(void)
{
    SDL_DelHintCallback(SDL_HINT_TIMER_RESOLUTION,
                        SDL_TimerResolutionChanged, NULL);

    SDL_SetSystemTimerResolution(0);  /* always release our timer resolution request. */

    start = 0;
    ticks_started = SDL_FALSE;
}

Uint64
SDL_GetTicks64(void)
{
    LARGE_INTEGER now;
    BOOL rc;

    if (!ticks_started) {
        SDL_TicksInit();
    }

    rc = QueryPerformanceCounter(&now);
    SDL_assert(rc != 0);  /* this should _never_ fail if you're on XP or later. */
    return (Uint64) (((now.QuadPart - start_ticks.QuadPart) * 1000) / ticks_per_second.QuadPart);
}

Uint64
SDL_GetPerformanceCounter(void)
{
    LARGE_INTEGER counter;
    const BOOL rc = QueryPerformanceCounter(&counter);
    SDL_assert(rc != 0);  /* this should _never_ fail if you're on XP or later. */
    return (Uint64) counter.QuadPart;
}

Uint64
SDL_GetPerformanceFrequency(void)
{
    LARGE_INTEGER frequency;
    const BOOL rc = QueryPerformanceFrequency(&frequency);
    SDL_assert(rc != 0);  /* this should _never_ fail if you're on XP or later. */
    return (Uint64) frequency.QuadPart;
}

void
SDL_Delay(Uint32 ms)
{
    /* Sleep() is not publicly available to apps in early versions of WinRT.
     *
     * Visual C++ 2013 Update 4 re-introduced Sleep() for Windows 8.1 and
     * Windows Phone 8.1.
     *
     * Use the compiler version to determine availability.
     *
     * NOTE #1: _MSC_FULL_VER == 180030723 for Visual C++ 2013 Update 3.
     * NOTE #2: Visual C++ 2013, when compiling for Windows 8.0 and
     *    Windows Phone 8.0, uses the Visual C++ 2012 compiler to build
     *    apps and libraries.
     */
#if defined(__WINRT__) && defined(_MSC_FULL_VER) && (_MSC_FULL_VER <= 180030723)
    static HANDLE mutex = 0;
    if (!mutex) {
        mutex = CreateEventEx(0, 0, 0, EVENT_ALL_ACCESS);
    }
    WaitForSingleObjectEx(mutex, ms, FALSE);
#else
    if (!ticks_started) {
        SDL_TicksInit();
    }

    Sleep(ms);
#endif
}

#endif /* SDL_TIMER_WINDOWS */

/* vi: set ts=4 sw=4 expandtab: */

kc3-lang/SDL/src/timer/windows

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kc3-lang/SDL /src/timer/windows