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timespec: Add timespec subtraction helpers

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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>
This commit is contained in:
Daniel Stone 2017-03-01 11:34:03 +00:00 committed by Pekka Paalanen
parent 37ad7e3bae
commit 839b63546d
2 changed files with 48 additions and 0 deletions
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26
shared/timespec-util.h
View File

@ -93,6 +93,20 @@ 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
@ -106,6 +120,18 @@ 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

22
tests/timespec-test.c
View File

@ -142,3 +142,25 @@ ZUC_TEST(timespec_test, timespec_add_msec)
ZUC_ASSERT_EQ(1002, r.tv_sec);
ZUC_ASSERT_EQ(2000001, r.tv_nsec);
}
ZUC_TEST(timespec_test, timespec_sub_to_nsec)
{
struct timespec a, b;
a.tv_sec = 1000;
a.tv_nsec = 1;
b.tv_sec = 1;
b.tv_nsec = 2;
ZUC_ASSERT_EQ((999L * NSEC_PER_SEC) - 1, timespec_sub_to_nsec(&a, &b));
}
ZUC_TEST(timespec_test, timespec_sub_to_msec)
{
struct timespec a, b;
a.tv_sec = 1000;
a.tv_nsec = 2000000L;
b.tv_sec = 2;
b.tv_nsec = 1000000L;
ZUC_ASSERT_EQ((998 * 1000) + 1, timespec_sub_to_msec(&a, &b));
}