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util: add function to subtract NTP timestamps

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This will be needed to work with monotonic timestamps, which don't have
a stable epoch and cannot be converted to timespec.
This commit is contained in:
Miroslav Lichvar 2021-11-10 14:28:53 +01:00
parent a97ca73704
commit a652ce7d0e
3 changed files with 21 additions and 1 deletions
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9
test/unit/util.c
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@ -34,7 +34,7 @@ test_unit(void)
{
struct timespec ts, ts2, ts3, ts4;
char buf[16], *s, *s2, *words[3];
NTP_int64 ntp_ts, ntp_fuzz;
NTP_int64 ntp_ts, ntp_ts2, ntp_fuzz;
NTP_int32 ntp32_ts;
struct timeval tv;
double x, y, nan, inf;
@ -114,6 +114,13 @@ test_unit(void)
#endif
TEST_CHECK(ts.tv_nsec == 999999999);
ntp_ts.hi = htonl(JAN_1970 - 1);
ntp_ts.lo = htonl(0xffffffff);
ntp_ts2.hi = htonl(JAN_1970 + 1);
ntp_ts2.lo = htonl(0x80000000);
TEST_CHECK(fabs(UTI_DiffNtp64ToDouble(&ntp_ts, &ntp_ts2) + 1.5) < 1e-9);
TEST_CHECK(fabs(UTI_DiffNtp64ToDouble(&ntp_ts2, &ntp_ts) - 1.5) < 1e-9);
UTI_AddDoubleToTimespec(&ts, 1e-9, &ts);
#if defined(HAVE_LONG_TIME_T) && NTP_ERA_SPLIT > 0
TEST_CHECK(ts.tv_sec == 1 + 0x100000000LL * (1 + (NTP_ERA_SPLIT - 1) / 0x100000000LL));

10
util.c
View file

@ -751,6 +751,16 @@ UTI_Ntp64ToTimespec(const NTP_int64 *src, struct timespec *dest)
/* ================================================== */
double
UTI_DiffNtp64ToDouble(const NTP_int64 *a, const NTP_int64 *b)
{
/* Don't convert to timespec to allow any epoch */
return (int32_t)(ntohl(a->hi) - ntohl(b->hi)) +
((double)ntohl(a->lo) - (double)ntohl(b->lo)) / (1.0e9 * NSEC_PER_NTP64);
}
/* ================================================== */
/* Maximum offset between two sane times */
#define MAX_OFFSET 4294967296.0

3
util.h
View file

@ -155,6 +155,9 @@ extern void UTI_TimespecToNtp64(const struct timespec *src, NTP_int64 *dest,
/* Convert an NTP timestamp into a timespec */
extern void UTI_Ntp64ToTimespec(const NTP_int64 *src, struct timespec *dest);
/* Calculate a - b in any epoch */
extern double UTI_DiffNtp64ToDouble(const NTP_int64 *a, const NTP_int64 *b);
/* Check if time + offset is sane */
extern int UTI_IsTimeOffsetSane(const struct timespec *ts, double offset);