/* IRCfs - IRC FileServ for *nix.
 * Copyright (C) 2002  Nick 'Zaf' Clifford <zaf@nrc.co.nz>
 * For licensing details, refer to the LICENSE file in the source 
 * code directory.
 */
#include "timeutil.h"
#include "runtime.h"


/* add_time(a,b,c)
 * a = b + c
 * Returns a.tv_sec
 */
time_t add_time(struct timeval *a, struct timeval *b, struct timeval *c)
{
	time_t usec;
	ASSERT(a);
	ASSERT(b);
	ASSERT(c);

	usec = b->tv_usec + c->tv_usec;
	a->tv_sec = b->tv_sec + c->tv_sec + usec / 1000000;
	a->tv_usec = usec % 1000000;

	return a->tv_sec;
}
	

/* sub_time(a,b,c)
 * a = b - c
 * Returns a.tv_sec
 * Does not return negative numbers. (Will round negative numbers to 0)
 */
time_t sub_time(struct timeval *a, struct timeval *b, struct timeval *c)
{
	ASSERT(a);
	ASSERT(b);
	ASSERT(c);
	// e = (c > a) ? 0 : (a-c);
	// a.b - c.d = (d>b) ? (e)-1.(10-d-b) : (e).(b-d)
	if (c->tv_sec > b->tv_sec)
		a->tv_sec = 0;
	else
		a->tv_sec = b->tv_sec - c->tv_sec;

	if (c->tv_usec > b->tv_usec) {
		if (a->tv_sec) {
			a->tv_sec--; // Decrement a, if not zero
			a->tv_usec = 1000000 - (c->tv_usec - b->tv_usec);
		} else
			a->tv_usec = 0;
	} else {
		a->tv_usec = b->tv_usec - c->tv_usec;
	}

	return a->tv_sec;
}
	
/* time_comp(a,b)
 * If a < b, returns -1
 * if a > b, returns 1
 * if a == b, returns 0
 */
int time_comp(struct timeval *a, struct timeval *b)
{
	ASSERT(a);
	ASSERT(b);
		
	if (a->tv_sec < b->tv_sec)
		return -1;
	if (a->tv_sec > b->tv_sec)
		return 1;
	/* a->tv_sec == b->tv_sec */
	if (a->tv_usec < b->tv_usec)
		return -1;
	if (a->tv_usec > b->tv_usec)
		return 1;
	/* a->tv_usec == b->tv_usec */
	return 0;
}