Symbian

开发平台：
C/C++

gettickcount.c：源码内容
							/* ***** BEGIN LICENSE BLOCK ***** 
 * Version: RCSL 1.0/RPSL 1.0 
 *  
 * Portions Copyright (c) 1995-2002 RealNetworks, Inc. All Rights Reserved. 
 *      
 * The contents of this file, and the files included with this file, are 
 * subject to the current version of the RealNetworks Public Source License 
 * Version 1.0 (the "RPSL") available at 
 * http://www.helixcommunity.org/content/rpsl unless you have licensed 
 * the file under the RealNetworks Community Source License Version 1.0 
 * (the "RCSL") available at http://www.helixcommunity.org/content/rcsl, 
 * in which case the RCSL will apply. You may also obtain the license terms 
 * directly from RealNetworks.  You may not use this file except in 
 * compliance with the RPSL or, if you have a valid RCSL with RealNetworks 
 * applicable to this file, the RCSL.  Please see the applicable RPSL or 
 * RCSL for the rights, obligations and limitations governing use of the 
 * contents of the file.  
 *  
 * This file is part of the Helix DNA Technology. RealNetworks is the 
 * developer of the Original Code and owns the copyrights in the portions 
 * it created. 
 *  
 * This file, and the files included with this file, is distributed and made 
 * available on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 
 * EXPRESS OR IMPLIED, AND REALNETWORKS HEREBY DISCLAIMS ALL SUCH WARRANTIES, 
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS 
 * FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 
 * 
 * Technology Compatibility Kit Test Suite(s) Location: 
 *    http://www.helixcommunity.org/content/tck 
 * 
 * Contributor(s): 
 *  
 * ***** END LICENSE BLOCK ***** */ 
#include "hxtypes.h"
#include "hxtick.h"
#ifdef _WIN32
/*
 * In 32bit Windows we have a HX_GET_BETTERTICKCOUNT()
 * which uses the queryPerformance interface for highly accurate times.
 * XXXKB: This implementation is now thread safe;
 */
ULONG32 GetBetterTickCount()
{
    static ULARGE_INTEGER s_ullPerformanceFrequency = { 0, 0 };
    static BOOL s_bFrequencyChecked = FALSE;
    ULARGE_INTEGER ullPerformanceCounter;
    
    do
    {
        if (s_ullPerformanceFrequency.LowPart)
        {
            if (QueryPerformanceCounter((union _LARGE_INTEGER*)
                                          &ullPerformanceCounter))
            {
                return (ULONG32) ((ullPerformanceCounter.QuadPart*1000) / 
                                  s_ullPerformanceFrequency.QuadPart);
            }
        }
        if (!s_bFrequencyChecked)
        {
            // Hopefully this is atomic kernel call:
            if (!QueryPerformanceFrequency((union _LARGE_INTEGER*)
                                           &s_ullPerformanceFrequency)
                // If the frequency > 32 bits, we lose range
                || s_ullPerformanceFrequency.HighPart 
                // If the frequency < 1000, we lose precision
                || (s_ullPerformanceFrequency.LowPart < 1000))
            {
                s_ullPerformanceFrequency.LowPart = 0;
            }
            s_bFrequencyChecked = TRUE;
        }
        
    } while (s_ullPerformanceFrequency.LowPart);
    
    return GetTickCount();
}
/*
 * In 32bit Windows we have a GetMSTickDouble32()
 * which uses the queryPerformance interface for highly accurate times.
 * XXXKB: This implementation is thread safe, returns milliseconds with
 * double precision.  We still wrap around at 2^32 -1 milliseconds.
 * We will have wraparound error if (maxCounter*1000 / maxFrequency) % (2^32 - 1)
 */                                 
#ifndef MAX_ULONG32_AS_DOUBLE
#define MAX_ULONG32_AS_DOUBLE	((double) ((ULONG32) 0xFFFFFFFF))
#endif
double GetMSTickDouble32()
{
    static double s_dFrequency = 0;
    static BOOL s_bFrequencyChecked = FALSE;
    double dTick;
    UINT32 ulQuotient;
    do
    {
        if (s_dFrequency)
        {
            ULARGE_INTEGER ullPerformanceCounter;
            if (QueryPerformanceCounter((union _LARGE_INTEGER*)
                                         &ullPerformanceCounter))
            {
                double dPerformanceCounter = 4294967296.0;
                dPerformanceCounter *= ullPerformanceCounter.HighPart;
                dPerformanceCounter += ullPerformanceCounter.LowPart;                         
                    
                // Convert out of range doubles here; is there a standard 
                // conversion from an out of range float64 to a uint32?
                // We can't use fmod here; it's not in the pncrt nor in
                // every Windows runtime:
                dTick = dPerformanceCounter*1000 / s_dFrequency;
                ulQuotient = (UINT32) (dTick / (MAX_ULONG32_AS_DOUBLE + 1));
                return dTick - (ulQuotient*(MAX_ULONG32_AS_DOUBLE + 1));
            }
        }
        if (!s_bFrequencyChecked)
        {
            ULARGE_INTEGER ullPerformanceFrequency;
            // Hopefully this is atomic kernel call:
            if (QueryPerformanceFrequency((union _LARGE_INTEGER*)
                                           &ullPerformanceFrequency)
                // If the frequency > 32 bits, we lose range
                && !(ullPerformanceFrequency.HighPart 
                     // If the frequency < 1000, we lose precision
                     || (ullPerformanceFrequency.LowPart < 1000)))
            {
                s_dFrequency = 4294967296.0;
                s_dFrequency *= ullPerformanceFrequency.HighPart;
                s_dFrequency += ullPerformanceFrequency.LowPart;
            }
            s_bFrequencyChecked = TRUE;
        }
        
    } while (s_dFrequency);
    
    return GetTickCount();
}
#endif // _WIN32

						