libstddjb
skalibs
skalibs
Software
skarnet.org
The following functions are declared in the skalibs/djbtime.h header, and implemented in the libskarnet.a or libskarnet.so library.
djbtime is a set of functions to convert tai_t and tain_t structures, and TAI time, from and to other time formats and user-friendly representations.
User-friendly time is calculated from UTC. Internal time computations should be performed on TAI time - because TAI flows linearly whereas UTC does not. To convert between UTC and TAI time, you need a leap second table. skalibs provides such a file in its src/etc/leapsecs.dat subdirectory, which is copied to /etc/leapsecs.dat at installation time (unless you specify a --prefix or --datadir option to configure). The /etc/leapsecs.dat file must remain accessible on your system, else time conversions will not be computed properly.
int utc_from_tai (uint64 *u, tai_t const *t)
Converts the absolute TAI64 time in *t to an UTC time, stored in
*u as an unsigned 64-bit integer. *u is actually 2^62
plus the number of seconds since the Epoch.
The function returns 1 if it succeeds, or 0 (and sets errno) if an
error occurs (for instance: the leap second table cannot be found).
int tai_from_utc (tai_t *t, uint64 u)
Converts the UTC time in u, stored
as an unsigned 64-bit integer (2^62 plus the number of seconds since
the Epoch), to a TAI64 time in *t.
The function returns 1 if it succeeds, or 0 (and sets errno) if an
error occurs (for instance: the leap second table cannot be found).
int ntp_from_tain (uint64 *ntp, tain_t const *a)
Converts the absolute TAI64N time in *a to a 64-bit NTP timestamp,
stored in *ntp. The higher 32 bits of *ntp represent a number
of seconds ; the lower 32 bits are the fractional part of the timestamp.
The function returns 1 if it succeeds, or 0 (and sets errno) if an
error occurs (for instance: the leap second table cannot be found, or
*a cannot be represented in the valid NTP range).
int tain_from_ntp (tain_t *a, uint64 ntp)
Converts the NTP timestamp in ntp to a TAI64N time in
*a.
The function returns 1 if it succeeds, or 0 (and sets errno) if an
error occurs (for instance: the leap second table cannot be found).
The following functions convert time between an internal representation and a broken-down struct tm. Conversions are performed to get leap seconds handling right, depending on whether skalibs has been configured for a TAI-10 or a UTC system clock, and on whether the current timezone takes leap seconds into account or not.
int localtm_from_tai (struct tm *tm, tai_t const *t, int lo)
Converts the TAI time in *t to broken-down GMT (if
lo is zero) or local (if lo is nonzero) time in
*tm.
The function returns 1 if it succeeds, or 0 (and sets errno) if an
error occurs (for instance: *t cannot be validly represented
in a struct tm).
int localtm_from_utc (struct tm *tm, uint64 u, int lo)
Converts the UTC time in u to broken-down GMT (if
lo is zero) or local (if lo is nonzero) time in
*tm.
The function returns 1 if it succeeds, or 0 (and sets errno) if an
error occurs (for instance: u cannot be validly represented
in a struct tm).
int localtm_from_sysclock (struct tm *tm, uint64 u, int lo)
Converts the time in u to broken-down GMT (if
lo is zero) or local (if lo is nonzero) time in
*tm. u will be interpreted as a TAI-10 value (with
--enable-tai-clock) or as a UTC value (without --enable-tai-clock).
The function returns 1 if it succeeds, or 0 (and sets errno) if an
error occurs (for instance: u cannot be validly represented
in a struct tm).
int utc_from_localtm (uint64 *u, struct tm const *tm)
Converts the broken-down local time in *tm to an UTC value
in *u.
The function returns 1 if it succeeds, or 0 (and sets errno) if an
error occurs.
int tai_from_localtm (tai_t *t, struct tm const *tm)
Converts the broken-down local time in *tm to a TAI value
in *t.
The function returns 1 if it succeeds, or 0 (and sets errno) if an
error occurs.
int sysclock_from_localtm (uint64 *u, struct tm const *tm)
Converts the broken-down local time in *tm to a value
in *u - either TAI-10 or UTC depending on your system clock.
The function returns 1 if it succeeds, or 0 (and sets errno) if an
error occurs.
The following functions use the localtmn_t type to hold both a broken-down time and a nanosecond count:
typedef struct localtmn_s localtmn_t, *localtmn_t_ref ;
struct localtmn_s
{
struct tm tm ;
uint32 nano ;
} ;
The prototypes are self-explaining:
int localtmn_from_tain (localtmn_t *tmn, tain_t const *a, int lo) ;
int tain_from_localtmn (tain_t *a, localtmn_t const *tmn) ;
int localtmn_from_sysclock (localtmn_t *tmn, tain_t const *a, int lo) ;
int sysclock_from_localtmn (tain_t *a, localtmn_t const *tmn) ;