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/*
* This file is Copyright (c) 2015 by the GPSD project
* BSD terms apply: see the file COPYING in the distribution root for details.
*/
#ifndef GPSD_TIMESPEC_H
#define GPSD_TIMESPEC_H
/* normalize a timespec
*
* three cases to note
* if tv_sec is positve, then tv_nsec must be positive
* if tv_sec is negative, then tv_nsec must be negative
* if tv_sec is zero, then tv_nsec may be positive or negative.
*
* this only handles the case where two normalized timespecs
* are added or subracted. (e.g. only a one needs to be borrowed/carried
*
* NOTE: this normalization is not the same as ntpd uses
*/
#define NS_IN_SEC 1000000000LL
#define MS_IN_SEC 1000000LL
/* return the difference between timespecs in nanoseconds
* int may be too small, 32 bit long is too small, floats are too imprecise,
* doubles are not quite precise enough
* MUST be long long to maintain precision on 32 bit code */
#define timespec_diff_ns(x, y) \
(long long)((((x).tv_sec-(y).tv_sec)*NS_IN_SEC)+(x).tv_nsec-(y).tv_nsec)
static inline void TS_NORM( struct timespec *ts)
{
if ( ( 1 <= ts->tv_sec ) ||
( (0 == ts->tv_sec ) && (0 <= ts->tv_nsec ) ) ) {
/* result is positive */
if ( NS_IN_SEC <= ts->tv_nsec ) {
/* borrow from tv_sec */
ts->tv_nsec -= NS_IN_SEC;
ts->tv_sec++;
} else if ( 0 > (ts)->tv_nsec ) {
/* carry to tv_sec */
ts->tv_nsec += NS_IN_SEC;
ts->tv_sec--;
}
} else {
/* result is negative */
if ( -NS_IN_SEC >= ts->tv_nsec ) {
/* carry to tv_sec */
ts->tv_nsec += NS_IN_SEC;
ts->tv_sec--;
} else if ( 0 < ts->tv_nsec ) {
/* borrow from tv_sec */
ts->tv_nsec -= NS_IN_SEC;
ts->tv_sec++;
}
}
}
/* normalize a timeval */
#define TV_NORM(tv) \
do { \
if ( MS_IN_SEC <= (tv)->tv_usec ) { \
(tv)->tv_usec -= MS_IN_SEC; \
(tv)->tv_sec++; \
} else if ( 0 > (tv)->tv_usec ) { \
(tv)->tv_usec += MS_IN_SEC; \
(tv)->tv_sec--; \
} \
} while (0)
/* convert timespec to timeval, with rounding */
#define TSTOTV(tv, ts) \
do { \
(tv)->tv_sec = (ts)->tv_sec; \
(tv)->tv_usec = ((ts)->tv_nsec + 500)/1000; \
TV_NORM( tv ); \
} while (0)
/* convert timeval to timespec */
#define TVTOTS(ts, tv) \
do { \
(ts)->tv_sec = (tv)->tv_sec; \
(ts)->tv_nsec = (tv)->tv_usec*1000; \
TS_NORM( ts ); \
} while (0)
/* subtract two timespec */
#define TS_SUB(r, ts1, ts2) \
do { \
(r)->tv_sec = (ts1)->tv_sec - (ts2)->tv_sec; \
(r)->tv_nsec = (ts1)->tv_nsec - (ts2)->tv_nsec; \
TS_NORM( r ); \
} while (0)
/* convert a timespec to a double.
* if tv_sec > 2, then inevitable loss of precision in tv_nsec
* so best to NEVER use TSTONS()
* WARNING replacing 1e9 with NS_IN_SEC causes loss of precision */
#define TSTONS(ts) ((double)((ts)->tv_sec + ((ts)->tv_nsec / 1e9)))
#define TIMESPEC_LEN 22 /* required length of a timespec buffer */
extern void timespec_str(const struct timespec *, char *, size_t);
#endif /* GPSD_TIMESPEC_H */
/* end */
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