D. J. Bernstein

The tai library interface

Times with 1-second precision

     #include <tai.h>

     struct tai t;
A struct tai value is an integer between 0 inclusive and 2^64 exclusive. The format of struct tai is designed to speed up common operations; applications should not look inside struct tai.

A struct tai variable is commonly used to store a TAI64 label. Each TAI64 label refers to one second of real time. TAI64 labels span a range of hundreds of billions of years.

A struct tai variable may also be used to store the numerical difference between two TAI64 labels.

Current time

     #include <tai.h>

     struct tai t;

tai_now puts the current time into t. More precisely: tai_now puts into t its best guess as to the TAI64 label for the 1-second interval that contains the current time.

This implementation of tai_now assumes that the time_t returned from the time function represents the number of TAI seconds since 1970-01-01 00:00:10 TAI. This matches the convention used by the Olson tz library in ``right'' mode.

Binary input and output

     #include <tai.h>

     struct tai t;
     char buf[TAI_PACK];

tai_pack converts a TAI64 label from internal format in t to external TAI64 format in buf.

tai_unpack converts a TAI64 label from external TAI64 format in buf to internal format in t.

TAI_PACK is 8.


     #include <tai.h>

     struct tai t;
     struct tai a;
     struct tai b;
     double d;
     int i;

     d = tai_approx(&t);
     i = tai_less(&a,&b);
tai_approx returns a double-precision approximation to t. The result of tai_approx is always nonnegative.

tai_less returns 1 if a is less than b, 0 otherwise.

tai_add adds a to b modulo 2^64 and puts the result into t. The inputs and output may overlap.

tai_sub subtracts b from a modulo 2^64 and puts the result into t. The inputs and output may overlap.