localtime.cxx

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#include <localtime.hxx>
#include <limits.h>
#include <unicode/timezone.h>
#include <memory>
 
const tools::Long DAY_SEC = 24 * 60 * 60;
const tools::Long YEAR_SEC = 365 * DAY_SEC;
const tools::Long FOURYEAR_SEC = 4 * YEAR_SEC + DAY_SEC;
#ifndef LONG_MAX
const long LONG_MAX = 2147483647;
#endif
//01-01-70 was a Thursday
const tools::Long BASE_DOW = 4;
 
bool LtgGmTime(tools::Long rtime, LtTm& rtm)
{
    if (rtime < 0)
    {
        return false;
    }
    //is-current-year-a-leap-year flag
    int islpyr = 0;
 
    tools::Long tmptim;
    tools::Long caltim = rtime;
    tmptim = static_cast<tools::Long>(caltim / FOURYEAR_SEC);
    caltim -= tmptim * FOURYEAR_SEC;
 
    //Determine which year of the interval
 
    // 1970, 1974, 1978,...,etc.
    tmptim = (tmptim * 4) + 70;
 
    if (caltim >= YEAR_SEC)
    {
        //1971, 1975, 1979,...,etc.
        tmptim++;
        caltim -= YEAR_SEC;
 
        if (caltim >= YEAR_SEC)
        {
            // 1972, 1976, 1980,...,etc.
            tmptim++;
            caltim -= YEAR_SEC;
 
            //Note, it takes 366 days-worth of seconds to get past a leap year.
            if (caltim >= (YEAR_SEC + DAY_SEC))
            {
                //1973, 1977, 1981,...,etc.
                tmptim++;
                caltim -= (YEAR_SEC + DAY_SEC);
            }
            else
            {
                //In a leap year after all, set the flag.
                islpyr++;
            }
        }
    }
 
    //tmptim now holds the value for tm_year. caltim now holds the
    //number of elapsed seconds since the beginning of that year.
 
    rtm.tm_year = tmptim;
 
    //Determine days since January 1 (0 - 365). This is the tm_yday value.
    //Leave caltim with number of elapsed seconds in that day.
 
    rtm.tm_yday = static_cast<tools::Long>(caltim / DAY_SEC);
    caltim -= rtm.tm_yday * DAY_SEC;
 
    //Determine months since January (0 - 11) and day of month (1 - 31)
 
    tools::Long const* mdays;
    if (islpyr)
    {
        static tools::Long const lpdays[]
            = { -1, 30, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 };
        mdays = lpdays;
    }
    else
    {
        static tools::Long const days[]
            = { -1, 30, 58, 89, 119, 150, 180, 211, 242, 272, 303, 333, 364 };
        mdays = days;
    }
 
    for (tmptim = 1; mdays[tmptim] < rtm.tm_yday; tmptim++)
        ;
 
    rtm.tm_mon = --tmptim;
 
    rtm.tm_mday = rtm.tm_yday - mdays[tmptim];
 
    //Determine days since Sunday (0 - 6)
 
    rtm.tm_wday = (static_cast<tools::Long>(rtime / DAY_SEC) + BASE_DOW) % 7;
 
    //Determine hours since midnight (0 - 23), minutes after the hour
    //(0 - 59), and seconds after the minute (0 - 59).
 
    rtm.tm_hour = static_cast<tools::Long>(caltim / 3600);
    caltim -= rtm.tm_hour * 3600;
 
    rtm.tm_min = static_cast<tools::Long>(caltim / 60);
    rtm.tm_sec = static_cast<tools::Long>(caltim - (rtm.tm_min) * 60);
 
    //adjust year & month
    rtm.tm_year += 1900;
    ++(rtm.tm_mon);
 
    return true;
};
bool LtgLocalTime(tools::Long rtime, LtTm& rtm)
{
    if (rtime < 0)
    {
        return false;
    }
 
    if ((rtime > 3 * DAY_SEC) && (rtime < LONG_MAX - 3 * DAY_SEC))
    {
        std::unique_ptr<icu::TimeZone> pLocalZone(icu::TimeZone::createDefault());
        tools::Long offset = (pLocalZone->getRawOffset()) / 1000;
        pLocalZone.reset();
        tools::Long ltime = rtime + offset;
        return LtgGmTime(ltime, rtm);
    }
    return false;
};
 
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