NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c++-part1/5435

Text File | 1996-08-05 | 4.6 KB | 205 lines

Path: newsfeed.internetmci.com!xmission!news
From: [e-mail]  ( Todd Knarr )
Newsgroups: comp.lang.c++
Subject: Re: Date class
Date: 4 Feb 1996 18:05:00 GMT
Organization: Chaos Central
Message-ID: <4f2sgc$[e-mail]>
References: <4f09k2$[e-mail]>
Reply-To: [e-mail] ( Todd Knarr )
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X-Newsreader: IBM NewsReader/2 v1.2

Here's the .C file that completes the Date class.

//
//  Classname : Date
//
//  Author    : Todd Knarr
//
//  Description    :
//      Provides a Date class which represents dates as Julian day numbers
//      ( days since 1 Jan 4713 BC ).
//      This class can handle all dates from  1 Jan 4713BC to 31 Dec 9999AD.
//
//      Note: Years AD are positive, years BC are negative. There is
//      no year 0AD, it goes from 1BC to 1AD. A year of 0 will be treated
//      as 1BC. No attempt is made to validate ranges. Physical errors
//      will not result from insane day-month combinations like the 87th
//      day of the 45th month, but the results will obviously not make
//      much sense.
//
//      Date conversion routines by Eric Bergman-Terrell,
//          Computer Language Dec 1990.
//

#include "date.h"

#include <time.h>

//
//  Function :  YmdToJd
//
//  Parameters     : int year, month, day
//
//  Return values  : long julian day
//
//  Description    :
//
long Date::YmdToJd( const int iYear, const int iMonth, const int iDay )
{
    long jul_day;

    int a,b;
    int year = iYear, month = iMonth, day = iDay;
    float year_corr;

    if ( year < 0 )
        year++;
    year_corr = ( year > 0 ? 0.0 : 0.75 );
    if ( month <= 2 )
    {
        year--;
        month += 12;
    }
    b = 0;
    if ( year * 10000.0 + month * 100.0 + day >= 15821015.0 )
    {
        a = year / 100;
        b = 2 - a + a / 4;
    }
    jul_day = (long) ( 365.25 * year - year_corr ) +
              (long) ( 30.6001 * ( month + 1 ) ) + day + 1720995L + b;

    return jul_day;
}

//
//  Function :  JdToYmd
//
//  Parameters     : long julian day, pointers to int year, month, day
//
//  Return values  : none
//
//  Description    :
//
void Date::JdToYmd( const long lJD, int *piYear, int *piMonth, int *piDay )
{
    long a, b, c, d, e, z, alpha;

    z = lJD;
    if ( z < 2299161L )
        a = z;
    else
    {
        alpha = (long) ( ( z - 1867216.25 ) / 36524.25 );
        a = z + 1 + alpha - alpha / 4;
    }
    b = a + 1524;
    c = (long) ( ( b - 122.1 ) / 365.25 );
    d = (long) ( 365.25 * c );
    e = (long) ( ( b - d ) / 30.6001 );
    *piDay = (int) b - d - (long) ( 30.6001 * e );
    *piMonth = (int) ( e < 13.5 ) ? e - 1 : e - 13;
    *piYear = (int) ( *piMonth > 2.5 ) ? ( c - 4716 ) : c - 4715;
    if ( *piYear <= 0 )
        *piYear -= 1;

    return;
}

//
//  Function :  ToString
//
//  Parameters     : pointer to string buffer to fill in
//
//  Return values  : none
//
//  Description    : Formats the Date into an ASCII representation.
//              This is the ASCII form of the long Julian day number.
//              The string is a fixed-length 11-character string, including
//              the NUL terminator;
//
void Date::ToString( char *szBuffer ) const
{
    int i;
    long Temp;

    Temp = lJulianDay;
    if ( Temp < 0L )
        szBuffer[0] = '-';
    else
        szBuffer[0] = '+';
    szBuffer[10] = '\0';
    for ( i = 9; i > 0; i-- )
    {
        szBuffer[i] = ( Temp % 10L ) + '0';
        Temp /= 10;
    }

    return;
}

//
//  Function :      DayOfYear
//
//  Parameters     : none
//
//  Return values  : day within year
//
//  Description    :
//
int Date::DayOfYear( void ) const
{
    int y, m, d;
    long soy;

    JdToYmd( lJulianDay, &y, &m, &d );
    soy = YmdToJd( y, 1, 1 );
    return (int) ( lJulianDay - soy + 1 );
}

//
//  Function :      ToSysTime
//
//  Parameters     : none
//
//  Return values  : converted result
//
//  Description    : Converts the date to a time_t value
//          representing midnight of that date.
//
time_t Date::ToSysTime( void ) const
{
    struct tm tmRep;
    int y, m, d;
    time_t t;

    JdToYmd( lJulianDay, &y, &m, &d );
    if ( y < 1970 )
    {
        y = 1970;
        m = 1;
        d = 1;
    }
    tmRep.tm_year = y - 1900 ;
    tmRep.tm_mon = m;
    tmRep.tm_mday = d;
    tmRep.tm_hour = 0;
    tmRep.tm_min = 0;
    tmRep.tm_sec = 0;
    tmRep.tm_isdst = 0;

    t = mktime( &tmRep );
    return t;
}

--
Todd Knarr : [e-mail]      |  finger for PGP public key
                                      |  Member, USENET Cabal

Seriously, I don't want to die just yet.  I don't care how
good-looking they are, I! don't! want! to! die!"
                                        -- Megazone ( UF1 )