/****************************************************************************
*                                                                           *
*   DT2UNIX.SPL Copyright 2021 (C) DSP Development Corporation              *
*                                                                           *
*   Author:      Randy Race                                                 *
*                                                                           *
*   Synopsis:    Converts Julian date and seconds to UNIX timestamp s       *
*                                                                           *
*   Revisions:   18 Jan 2021     RRR     Creation                           *
*                                                                           *
****************************************************************************/


#if @HELP_DT2UNIX

    DT2UNIX

    Purpose: Converts Julian date and clock seconds to UNIX timestamps.

    Syntax:  DT2UNIX(date, time)

              date - Optional. A string or integer Julian date, the
                     input date. Defaults to the current date.

              time - Optional. A string or real TOD, the input time. Defaults
                     to the current time.

    Returns: A scalar or series of Unix timestamps

    Example:
             udt = dt2unix("1-1-2021", "12:00:00");
             dtu = unix2dt(edt);

             udt == 1609502400.0
             dtu == "1/1/2021 12:00:00.000"

    Example:
             W1: {julstr("1-1-1999"), julstr("1-10-1999"), julstr("4-2-1999")}
             W2: {todstr("12:00"), todstr("14:00"), todstr("9:35")}
             W3: dt2unix(w1, w2)
             W4: unix2dt(w3)

             W3 == {915192000.0, 915976800.0, 923045700.0}

             W4 contains the date and time values:

              01/01/1999  12:00:00.000
              01/10/1999  14:00:00:000
              04/02/1999   9:35:00.000

    Remarks:
             A Unix timestamp is a real value that represents the number
             of seconds that have elapsed since midnight January 1, 1970 UTC
             time. The integer part is the whole number of days and the
             fractional part is the fraction of a day.
           
             See UNIX2DT to convert an Unix timestamp to a Julian date and
             clock time value.

             See DT2TIMESTAMP to convert date time values to internal
             timestamps suitable for date time arithmetic.

    See Also:
             DT2TIMESTAMP
             DTXY
             JULSTR
             LOCAL2UTC
             STRJUL
             STRTOD
             TIMESTAMP2DT
             TODSTR
             UNIX2DT
             UTC2LOCAL
             XYDT
#endif


/* convert date and time to unix timestamp */
dt2unix(date = getdate(), time = getutctime(), startdate = "1-1-1970")
{
        local unixdt;

        /* parse inputs */
        (date, time, startdate) = dt2_parse_args(date, time, startdate);

        /* start date as julian */
        startjul = julstr(startdate);
        
        /* unix seconds for each pair of date/time columns */
        unixdt = dt2unix_iterate(date, time, startjul);

        return(unixdt);
}


/* iterate on pairs of date/time series */
ITERATE dt2unix_iterate(date, time, startjul)
{
        local unixdt;

        /* unix date offset */
        unixdt = (date - startjul) * 86400 + time;

        if (isarray(unixdt))
        {
                setmatrix(unixdt, 0);
                setvunits(unixdt, "s");
        }

        return(unixdt);
}