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Diffstat (limited to 'contrib/ntp/include/timespecops.h')
| -rw-r--r-- | contrib/ntp/include/timespecops.h | 222 |
1 files changed, 222 insertions, 0 deletions
diff --git a/contrib/ntp/include/timespecops.h b/contrib/ntp/include/timespecops.h new file mode 100644 index 000000000000..17a9b680681e --- /dev/null +++ b/contrib/ntp/include/timespecops.h @@ -0,0 +1,222 @@ +/* + * timespecops.h -- calculations on 'struct timespec' values + * + * Written by Juergen Perlinger (perlinger@ntp.org) for the NTP project. + * The contents of 'html/copyright.html' apply. + * + * Rationale + * --------- + * + * Doing basic arithmetic on a 'struct timespec' is not exceedingly + * hard, but it requires tedious and repetitive code to keep the result + * normalised. We consider a timespec normalised when the nanosecond + * fraction is in the interval [0 .. 10^9[ ; there are multiple value + * pairs of seconds and nanoseconds that denote the same time interval, + * but the normalised representation is unique. No two different + * intervals can have the same normalised representation. + * + * Another topic is the representation of negative time intervals. + * There's more than one way to this, since both the seconds and the + * nanoseconds of a timespec are signed values. IMHO, the easiest way is + * to use a complement representation where the nanoseconds are still + * normalised, no matter what the sign of the seconds value. This makes + * normalisation easier, since the sign of the integer part is + * irrelevant, and it removes several sign decision cases during the + * calculations. + * + * As long as no signed integer overflow can occur with the nanosecond + * part of the operands, all operations work as expected and produce a + * normalised result. + * + * The exception to this are functions fix a '_fast' suffix, which do no + * normalisation on input data and therefore expect the input data to be + * normalised. + * + * Input and output operands may overlap; all input is consumed before + * the output is written to. + */ +#ifndef TIMESPECOPS_H +#define TIMESPECOPS_H + +#include <sys/types.h> +#include <stdio.h> +#include <math.h> + +#include "ntp.h" +#include "timetoa.h" + + +/* nanoseconds per second */ +#define NANOSECONDS 1000000000 + +/* predicate: returns TRUE if the nanoseconds are in nominal range */ +#define timespec_isnormal(x) \ + ((x)->tv_nsec >= 0 && (x)->tv_nsec < NANOSECONDS) + +/* predicate: returns TRUE if the nanoseconds are out-of-bounds */ +#define timespec_isdenormal(x) (!timespec_isnormal(x)) + + + + +/* make sure nanoseconds are in nominal range */ +extern struct timespec normalize_tspec(struct timespec x); + +/* x = a + b */ +static inline struct timespec +add_tspec( + struct timespec a, + struct timespec b + ) +{ + struct timespec x; + + x = a; + x.tv_sec += b.tv_sec; + x.tv_nsec += b.tv_nsec; + + return normalize_tspec(x); +} + +/* x = a + b, b is fraction only */ +static inline struct timespec +add_tspec_ns( + struct timespec a, + long b + ) +{ + struct timespec x; + + x = a; + x.tv_nsec += b; + + return normalize_tspec(x); +} + +/* x = a - b */ +static inline struct timespec +sub_tspec( + struct timespec a, + struct timespec b + ) +{ + struct timespec x; + + x = a; + x.tv_sec -= b.tv_sec; + x.tv_nsec -= b.tv_nsec; + + return normalize_tspec(x); +} + +/* x = a - b, b is fraction only */ +static inline struct timespec +sub_tspec_ns( + struct timespec a, + long b + ) +{ + struct timespec x; + + x = a; + x.tv_nsec -= b; + + return normalize_tspec(x); +} + +/* x = -a */ +static inline struct timespec +neg_tspec( + struct timespec a + ) +{ + struct timespec x; + + x.tv_sec = -a.tv_sec; + x.tv_nsec = -a.tv_nsec; + + return normalize_tspec(x); +} + +/* x = abs(a) */ +struct timespec abs_tspec(struct timespec a); + +/* + * compare previously-normalised a and b + * return 1 / 0 / -1 if a < / == / > b + */ +extern int cmp_tspec(struct timespec a, struct timespec b); + +/* + * compare possibly-denormal a and b + * return 1 / 0 / -1 if a < / == / > b + */ +static inline int +cmp_tspec_denorm( + struct timespec a, + struct timespec b + ) +{ + return cmp_tspec(normalize_tspec(a), normalize_tspec(b)); +} + +/* + * test previously-normalised a + * return 1 / 0 / -1 if a < / == / > 0 + */ +extern int test_tspec(struct timespec a); + +/* + * test possibly-denormal a + * return 1 / 0 / -1 if a < / == / > 0 + */ +static inline int +test_tspec_denorm( + struct timespec a + ) +{ + return test_tspec(normalize_tspec(a)); +} + +/* return LIB buffer ptr to string rep */ +static inline const char * +tspectoa( + struct timespec x + ) +{ + return format_time_fraction(x.tv_sec, x.tv_nsec, 9); +} + +/* + * convert to l_fp type, relative and absolute + */ + +/* convert from timespec duration to l_fp duration */ +extern l_fp tspec_intv_to_lfp(struct timespec x); + +/* x must be UN*X epoch, output will be in NTP epoch */ +static inline l_fp +tspec_stamp_to_lfp( + struct timespec x + ) +{ + l_fp y; + + y = tspec_intv_to_lfp(x); + y.l_ui += JAN_1970; + + return y; +} + +/* convert from l_fp type, relative signed/unsigned and absolute */ +extern struct timespec lfp_intv_to_tspec(l_fp x); +extern struct timespec lfp_uintv_to_tspec(l_fp x); + +/* + * absolute (timestamp) conversion. Input is time in NTP epoch, output + * is in UN*X epoch. The NTP time stamp will be expanded around the + * pivot time *p or the current time, if p is NULL. + */ +extern struct timespec lfp_stamp_to_tspec(l_fp x, const time_t *pivot); + +#endif /* TIMESPECOPS_H */ |