weston/shared/timespec-util.h
Daniel Stone 839b63546d timespec: Add timespec subtraction helpers
Add helpers to subtract two timespecs, then return the difference in
either milliseconds or nanoseconds. These will be used to compare
timestamps during the repaint cycle.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Suggested-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
2017-03-13 14:20:06 +02:00

148 lines
3.7 KiB
C

/*
* Copyright © 2014 - 2015 Collabora, Ltd.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice (including the
* next paragraph) shall be included in all copies or substantial
* portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#ifndef TIMESPEC_UTIL_H
#define TIMESPEC_UTIL_H
#include <stdint.h>
#include <assert.h>
#define NSEC_PER_SEC 1000000000
/* Subtract timespecs
*
* \param r[out] result: a - b
* \param a[in] operand
* \param b[in] operand
*/
static inline void
timespec_sub(struct timespec *r,
const struct timespec *a, const struct timespec *b)
{
r->tv_sec = a->tv_sec - b->tv_sec;
r->tv_nsec = a->tv_nsec - b->tv_nsec;
if (r->tv_nsec < 0) {
r->tv_sec--;
r->tv_nsec += NSEC_PER_SEC;
}
}
/* Add a nanosecond value to a timespec
*
* \param r[out] result: a + b
* \param a[in] base operand as timespec
* \param b[in] operand in nanoseconds
*/
static inline void
timespec_add_nsec(struct timespec *r, const struct timespec *a, int64_t b)
{
r->tv_sec = a->tv_sec + (b / NSEC_PER_SEC);
r->tv_nsec = a->tv_nsec + (b % NSEC_PER_SEC);
if (r->tv_nsec >= NSEC_PER_SEC) {
r->tv_sec++;
r->tv_nsec -= NSEC_PER_SEC;
} else if (r->tv_nsec < 0) {
r->tv_sec--;
r->tv_nsec += NSEC_PER_SEC;
}
}
/* Add a millisecond value to a timespec
*
* \param r[out] result: a + b
* \param a[in] base operand as timespec
* \param b[in] operand in milliseconds
*/
static inline void
timespec_add_msec(struct timespec *r, const struct timespec *a, int64_t b)
{
return timespec_add_nsec(r, a, b * 1000000);
}
/* Convert timespec to nanoseconds
*
* \param a timespec
* \return nanoseconds
*/
static inline int64_t
timespec_to_nsec(const struct timespec *a)
{
return (int64_t)a->tv_sec * NSEC_PER_SEC + a->tv_nsec;
}
/* Subtract timespecs and return result in nanoseconds
*
* \param a[in] operand
* \param b[in] operand
* \return to_nanoseconds(a - b)
*/
static inline int64_t
timespec_sub_to_nsec(const struct timespec *a, const struct timespec *b)
{
struct timespec r;
timespec_sub(&r, a, b);
return timespec_to_nsec(&r);
}
/* Convert timespec to milliseconds
*
* \param a timespec
* \return milliseconds
*
* Rounding to integer milliseconds happens always down (floor()).
*/
static inline int64_t
timespec_to_msec(const struct timespec *a)
{
return (int64_t)a->tv_sec * 1000 + a->tv_nsec / 1000000;
}
/* Subtract timespecs and return result in milliseconds
*
* \param a[in] operand
* \param b[in] operand
* \return to_milliseconds(a - b)
*/
static inline int64_t
timespec_sub_to_msec(const struct timespec *a, const struct timespec *b)
{
return timespec_sub_to_nsec(a, b) / 1000000;
}
/* Convert milli-Hertz to nanoseconds
*
* \param mhz frequency in mHz, not zero
* \return period in nanoseconds
*/
static inline int64_t
millihz_to_nsec(uint32_t mhz)
{
assert(mhz > 0);
return 1000000000000LL / mhz;
}
#endif /* TIMESPEC_UTIL_H */