ntptime.c

基于SNTP协议的时间同步客户端的c代码。其中计算传输时间偏移和同步误差都在客户端实现。可顺利移植到DSP上

#include "NtpTime.h"
#include "datatype.h"
#include <stdio.h>
#include <windows.h>
#define FALSE               0

SYSTEMTIME st;

CNtpTimePacket host2network(CNtpTimePacket ntp)  //transform the host byte order to network byte order,before filling the packet
{
	ntp.m_dwInteger = htonl(ntp.m_dwInteger);
	ntp.m_dwFractional = htonl(ntp.m_dwFractional);
	return ntp;
}
CNtpTimePacket network2host(CNtpTimePacket packet) //transform the network byte order to host byte order,after receiving the packet
{ 
	CNtpTimePacket hosttime;
	hosttime.m_dwFractional = ntohl(packet.m_dwFractional);
	hosttime.m_dwInteger = ntohl(packet.m_dwInteger);

	return hosttime;
}

////////////////////////////////////////////////////////////////////////////

CNtpTimePacket Systemtime2CNtpTimePacket(SYSTEMTIME st) //transform year,month,day,h,m,s to 2 packets of 32 bit
{  
	CNtpTimePacket t;
	//Currently this function only operates correctly in 
	//the 1900 - 2036 primary epoch defined by NTP
 
	long Seconds;
	long JD = GetJulianDay(st.wYear, st.wMonth, st.wDay);
	JD -= JAN_1ST_1900;   //year,month,day form to 32bit data

	assert(JD >= 0); //NTP only supports dates greater than 1900
	Seconds = JD;
	Seconds = (Seconds * 24) + st.wHour;
	Seconds = (Seconds * 60) + st.wMinute;
	Seconds = (Seconds * 60) + st.wSecond;
	assert(Seconds <= 0xFFFFFFFF); //NTP Only supports up to 2036
	t.m_dwInteger=Seconds;
	t.m_dwFractional=Ms2NtpFraction(st.wMilliseconds);
	return t;
}


SYSTEMTIME CNtpTimePacket2Systemtime(CNtpTimePacket pNtpTime)//transform  2 packets of 32 bit to year,month,day
{
	//Currently this function only operates correctly in 
	//the 1900 - 2036 primary epoch defined by NTP

	SYSTEMTIME st;
    ulong s = pNtpTime.m_dwInteger;  //integer part of pNtpTime to s
	long      JD;
	long      d;
	long      m;
	long      j;
	long      y;
	st.wSecond = (u16_t)(s % 60);
	s /= 60;
	st.wMinute = (u16_t)(s % 60);
	s /= 60;
	st.wHour = (u16_t)(s % 24);
	s /= 24;
	JD = s + JAN_1ST_1900;
	st.wDayOfWeek = (u16_t)((JD + 1) % 7);

    j = JD - 1721119;
    y = (4 * j - 1) / 146097;
    j = 4 * j - 1 - 146097 * y;
    d = j / 4;
    j = (4 * d + 3) / 1461;
    d = 4 * d + 3 - 1461 * j;
    d = (d + 4) / 4;
    m = (5 * d - 3) / 153;
    d = 5 * d - 3 - 153 * m;
    d = (d + 5) / 5;
    y = 100 * y + j;
    if (m < 10)
        m = m + 3;
    else
    {
        m = m - 9;
        y = y + 1;
    }

	  	st.wYear = (u16_t) y;
		st.wMonth= (u16_t) m;
		st.wDay = (u16_t) d;
	    st.wMilliseconds = NtpFraction2Ms(pNtpTime.m_dwFractional);
	return st;
}

long GetJulianDay(u16_t Year, u16_t Month, u16_t Day) //transform year,month,day to 1 integer of 32 bit
{
	long    c;
	long    ya;
	long    j;
	long    y = (long) Year;
	long    m = (long) Month;
	long    d = (long) Day;

    if (m > 2)
        m = m - 3;
    else
    {
        m = m + 9;
        y = y - 1;
    }
    c = y / 100;
    ya = y - 100 * c;
    j = (146097L * c) / 4 + (1461L * ya) / 4 + (153L * m + 2) / 5 + d + 1721119L;
    return j;
}


double CNtpTimePacket2Double(CNtpTimePacket pNtpTime) //transform 2 packets of 32 bit to double packet Round trip delay and c-s clock offset
{
	double t;                               
    t = (pNtpTime.m_dwInteger << 32) +NtpFraction2Second (pNtpTime.m_dwFractional);
	return t;
}

CNtpTimePacket Double2CNtpTimePacket(double dt) //transform double packet Round trip delay and c-s clock offset to 2 packets of 32 bit
{                                          
	CNtpTimePacket  t;
	t.m_dwInteger= (ulong) (dt);    //force dt to 1 integer of 32 bit，drop the fractional part
	NTP_TO_SECOND=(((double)1.0)/0xFFFFFFFF);   
	t.m_dwFractional=(ulong) (dt /NTP_TO_SECOND);    
	return t;
}

ulong Ms2NtpFraction(u16_t wMilliSeconds)
{
    assert(wMilliSeconds < 1000);
    return m_Ms2NTP[wMilliSeconds];   //fractional part is the 32bit data in look up table 
}

  
u16_t NtpFraction2Ms(ulong dwFraction)
{
    NTP_FRACTIONAL_TO_MS = (((double)1000.0)/0xFFFFFFFF);
	return (u16_t) ((((double) dwFraction) * NTP_FRACTIONAL_TO_MS) + 0.5);
} 

double NtpFraction2Second(ulong dwFraction) //fractional part to seconds,transform 32 bit integer to 0.xxxxxx s
{
    double   d = (double) dwFraction;
    NTP_TO_SECOND=(((double)1.0)/0xFFFFFFFF);
    d *= NTP_TO_SECOND;
    return ((double) dwFraction) * NTP_TO_SECOND;
}
 

CNtpTimePacket myGetCurrentTime()
{
    SYSTEMTIME st;
    GetSystemTime(&st);
    return Systemtime2CNtpTimePacket(st);
}
 
int  SetClientTime(CNtpTimePacket *NewTime)  //system get the new time
{
	int bSuccess = FALSE;
	SYSTEMTIME st =CNtpTimePacket2Systemtime(*NewTime);
	bSuccess = SetSystemTime(&st);
	if (!bSuccess)
	     printf("Failed in call to set the system time\n");

    return bSuccess;
}