/* nstime.c
 * Routines for manipulating nstime_t structures
 *
 * Copyright (c) 2005 MX Telecom Ltd. <richardv@mxtelecom.com>
 * 
 * $Id$
 *
 * Ethereal - Network traffic analyzer
 * By Gerald Combs <gerald@ethereal.com>
 * Copyright 1998 Gerald Combs
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 */

#include "nstime.h"

/* this is #defined so that we can clearly see that we have the right number of
   zeros, rather than as a guard against the number of nanoseconds in a second
   changing ;) */
#define NS_PER_S 1000000000

/*
 * function: get_timedelta
 * delta = b - a
 */

void get_timedelta(nstime_t *delta, const nstime_t *b, const nstime_t *a )
{
    if (b->secs == a->secs) {
        /* The seconds part of b is the same as the seconds part of a, so if
           the nanoseconds part of the first time is less than the nanoseconds
           part of a, b is before a.  The nanoseconds part of the delta should
           just be the difference between the nanoseconds part of b and the
           nanoseconds part of a; don't adjust the seconds part of the delta,
           as it's OK if the nanoseconds part is negative, and an overflow
           can never result. */
        delta->secs = 0;
        delta->nsecs = b->nsecs - a->nsecs;
    } else if (b->secs <= a->secs) {
        /* The seconds part of b is less than the seconds part of a, so b is
           before a.

           Both the "seconds" and "nanoseconds" value of the delta
           should have the same sign, so if the difference between the
           nanoseconds values would be *positive*, subtract 1,000,000,000
           from it, and add one to the seconds value. */
        delta->secs = b->secs - a->secs;
        delta->nsecs = b->nsecs - a->nsecs;
        if(delta->nsecs > 0) {
            delta->nsecs -= NS_PER_S;
            delta->secs ++;
        }
    } else {
        delta->secs = b->secs - a->secs;
        delta->nsecs = b->nsecs - a->nsecs;
        if(delta->nsecs < 0) {
            delta->nsecs += NS_PER_S;
            delta->secs --;
        }
    }
}

/*
 * function: get_timesum
 * sum = a + b
 */

void get_timesum(nstime_t *sum, const nstime_t *a, const nstime_t *b)
{
    sum->secs = a->secs + b->secs;
    sum->nsecs = a->nsecs + b->nsecs;
    if(sum->nsecs>=NS_PER_S || (sum->nsecs>0 && sum->secs<0)){
        sum->nsecs-=NS_PER_S;
        sum->secs++;
    } else if(sum->nsecs<=-NS_PER_S || (sum->nsecs<0 && sum->secs>0)) {
        sum->nsecs+=NS_PER_S;
        sum->secs--;
    }    
}