time.c

linux环境下用纯c写的RTP协议的通用开发库

/* time.c - timeadd, timesub, timeflatten, timeunflatten, timecmp */

#include <util.h>
#include <time.h>

/*-----------------------------------------------------------------------
 * timeadd - add two struct timespecs
 *-----------------------------------------------------------------------
 */
struct timespec
timeadd(struct timespec a, struct timespec b)
{

	b.tv_sec = -b.tv_sec;
	b.tv_nsec = -b.tv_nsec;
  
	return timesub(a, b);
}

/*-----------------------------------------------------------------------
 * timesub - subtract struct timespec b from a
 *-----------------------------------------------------------------------
 */
struct timespec
timesub(struct timespec a, struct timespec b)
{

	struct timespec c;
  
	c.tv_sec = a.tv_sec - b.tv_sec;
	c.tv_nsec = a.tv_nsec - b.tv_nsec;
  
	/* borrow if necessary */
	if (c.tv_nsec < 0) {
		c.tv_nsec += 1000000000;
		c.tv_sec--;
	}
	else if (c.tv_nsec > 1000000000) {
		c.tv_nsec -= 1000000000;
		c.tv_sec++;
	}
	return c;
}

/*-----------------------------------------------------------------------
 * timeflatten - convert a struct timespec to a flat time value
 *-----------------------------------------------------------------------
 */
mediatime_t 
timeflatten(struct timespec t, int clkrt)
{

	int rv;
	double d;

	rv = t.tv_sec * clkrt;

	d = (double) t.tv_nsec * .000000001;
	d *= (double) clkrt;

	rv += (int) d;

	return rv;
}

/*------------------------------------------------------------------------
 * timeunflatten - convert a flat time value to a struct timespec
 *------------------------------------------------------------------------
 */
struct timespec
timeunflatten(mediatime_t t, int clkrt)
{

	struct timespec	ts;
	double	d;

	ts.tv_sec = t / clkrt;
	d = ((double) (t % clkrt)) / ((double) clkrt);
	ts.tv_nsec = (int) (d * (double) 1000000000);

	return ts;
}

/*------------------------------------------------------------------------
 * timecmp - compare two strucxt timespecs. Return -1 if a is after b, 
 * 1 if b is after a, or 0 if equal. Yes, this is backward wrt to 
 * convention.
 *------------------------------------------------------------------------
 */
int
timecmp(struct timespec a, struct timespec b)
{
  
	if (a.tv_sec < b.tv_sec)
		return 1;
  
	if (a.tv_sec > b.tv_sec)
		return -1;    

	if (a.tv_nsec < b.tv_nsec)
		return 1;
  
	if (a.tv_nsec > b.tv_nsec)
		return -1;

	return 0;
}