ntptime.h

著名的 helix realplayer 基于手机 symbian 系统的 播放器全套源代码

/* ***** 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 
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 * 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. 
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 * This file, and the files included with this file, is distributed and made 
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 * EXPRESS OR IMPLIED, AND REALNETWORKS HEREBY DISCLAIMS ALL SUCH WARRANTIES, 
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 * ***** END LICENSE BLOCK ***** */ 

#ifndef _NTPTIME_H_
#define _NTPTIME_H_

#include "timeval.h"

/*
 * Number of seconds between 1-Jan-1900 and 1-Jan-1970
 */
#define GETTIMEOFDAY_TO_NTP_OFFSET 2208988800UL

#if !defined(MAX_UINT32)
#define MAX_UINT32		    0xFFFFFFFF
#endif

class NTPTime
{
public:

    // constructors
    NTPTime();
    NTPTime(UINT32 ulSec, UINT32 ulFraction);
    NTPTime(UINT32 mSec);
    NTPTime(Timeval tv);
    NTPTime(const NTPTime& lhs);

    // assignment
    NTPTime& operator=(const NTPTime& lhs);

    // conversion to ms
    operator UINT32();

    // arithmetic
    NTPTime operator+(const NTPTime& lhs);
    NTPTime operator-(const NTPTime& lhs);
    NTPTime& operator+=(const NTPTime& lhs);
    NTPTime& operator-=(const NTPTime& lhs);

    // comparison
    INT32 compare(const NTPTime& lhs) const;
    UINT32 toMSec();

    UINT32 m_ulSecond;
    UINT32 m_ulFraction;

private:
    UINT32 usec2ntp(UINT32 uSec);
    void fromMSec(INT32 mSec);
    void fromTimeval(Timeval tv);
};

/*
 * convert microseconds to fraction of second * 2^32 (i.e., the lsw of
 * a 64-bit ntp timestamp).  This routine uses the factorization
 * 2^32/10^6 = 4096 + 256 - 1825/32 which results in a max conversion
 * error of 3 * 10^-7 and an average error of half that.
 */
inline UINT32 NTPTime::usec2ntp(UINT32 uSec)
{
	UINT32 t = (uSec * 1825) >> 5;
	return ((uSec << 12) + (uSec << 8) - t);
}

inline void NTPTime::fromTimeval(Timeval tv)
{
    m_ulSecond = (UINT32)tv.tv_sec + GETTIMEOFDAY_TO_NTP_OFFSET;
    m_ulFraction = usec2ntp((UINT32)tv.tv_usec);
}

inline BOOL operator==(const NTPTime& t1, const NTPTime& t2)
{
    return t1.compare(t2) == 0;
}

inline BOOL operator!=(const NTPTime& t1, const NTPTime& t2)
{
    return t1.compare(t2) != 0;
}

inline BOOL operator<(const NTPTime& t1, const NTPTime& t2)
{
    return t1.compare(t2) < 0;
}

inline BOOL operator>(const NTPTime& t1, const NTPTime& t2)
{
    return t1.compare(t2) > 0;
}

inline BOOL operator<=(const NTPTime& t1, const NTPTime& t2)
{
    return t1.compare(t2) <= 0;
}

inline BOOL operator>=(const NTPTime& t1, const NTPTime& t2)
{
    return t1.compare(t2) >= 0;
}

#endif /* _NTPTIME_H_ */