Geografic-Information-System/lib/datetime/tz1.c

/*
 * Copyright (C) 1995.  Bill Brown <brown@gis.uiuc.edu> & Michael Shapiro
 *
 * This program is free software under the GPL (>=v2)
 * Read the file GPL.TXT coming with GRASS for details.
 */
#include <grass/datetime.h>


static int have(int x, const DateTime * dt)
{
    return datetime_is_between(x, dt->from, dt->to);
}


/*!
 * \brief 
 *
 * returns 0 on success
 *
 *  \param dt
 *  \param minutes
 *  \return int
 */

int datetime_check_timezone(const DateTime * dt, int minutes)
{
    if (!datetime_is_absolute(dt))
	return datetime_error(-1, "datetime not absolute");
    if (!have(DATETIME_MINUTE, dt))
	return datetime_error(-2, "datetime has no minute");
    if (!datetime_is_valid_timezone(minutes))
	return datetime_error(-3, "invalid datetime timezone");

    return 0;
}


/*!
 * \brief 
 *
 * returns 0 on success
 *
 *  \param dt
 *  \param minutes
 *  \return int
 */

int datetime_get_timezone(const DateTime * dt, int *minutes)
{
    int stat;

    stat = datetime_check_timezone(dt, dt->tz);
    if (stat == 0)
	*minutes = dt->tz;

    return stat;
}


/*!
 * \brief 
 *
 * returns 0 on success
 *
 *  \param dt
 *  \param minutes
 *  \return int
 */

int datetime_set_timezone(DateTime * dt, int minutes)
{
    int stat;

    stat = datetime_check_timezone(dt, minutes);
    if (stat == 0)
	dt->tz = minutes;

    return stat;
}

/*!
 * \brief 
 *
 * unsets timezone in 'dt'
 * returns 0
 *
 *  \param dt
 *  \return int
 */

int datetime_unset_timezone(DateTime * dt)
{
    dt->tz = -9999;

    return 0;
}


/*!
 * \brief 
 *
 * Returns:  
 * 1 OK: -720 <= minutes <= 780 (720 = 12 hours; 780 = 13 hours)  
 * 0 NOT OK 
 *
 *  \param minutes
 *  \return int
 */

int datetime_is_valid_timezone(int minutes)
{
    return (minutes >= -720 && minutes <= 780);
}