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. The --enable-right-tz configure option is used in determining how the conversion should proceed. If the --enable-tai-clock and --enable-right-tz configure options have been both enabled or both disabled, everything is naturally converted as it should be. If only one of them has been enabled, unholy magic happens here to get the correct broken-down time despite the timezone definition being wrong.
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_ref tmn, tain_t const *a, int lo) ;
int tain_from_localtmn (tain_t *a, localtmn_t const *tmn) ;
int localtmn_from_sysclock (localtmn_t_ref tmn, tain_t const *a, int lo) ;
int sysclock_from_localtmn (tain_t *a, localtmn_t const *tmn) ;