.TH taia 3
.SH NAME
taia \- manipulate times with 1-attosecond precision
.SH SYNTAX
.B #include <taia.h>

double \fBtaia_approx\fP(&\fIt\fR);
.br
double \fBtaia_frac\fP(&\fIt\fR);
.br
void \fBtaia_tai\fP(&\fIt\fR,&\fIsec\fR);

int \fBtaia_less\fP(&\fIa\fR,&\fIb\fR);
.br
void \fBtaia_add\fP(&\fIt\fR,&\fIa\fR,&\fIb\fR);
.br
void \fBtaia_sub\fP(&\fIt\fR,&\fIa\fR,&\fIb\fR);
.br
void \fBtaia_half\fP(&\fIt\fR,&\fIa\fR);

unsigned int \fBtaia_fmtfrac\fP(\fIs\fR,&\fIt\fR);

struct taia \fIt\fR;
.br
struct taia \fIa\fR;
.br
struct taia \fIb\fR;
.br
struct tai \fIsec\fR;
.br
char *\fIs\fR;
.SH DESCRIPTION
A
.B struct taia
stores an integer between 0 inclusive and 2^64x10^18 exclusive.
The format of
.B struct taia
is designed to speed up common operations;
applications should not look inside
.B struct taia\fR.

A
.B struct taia
variable is commonly used to store
a TAI64NA label.
Each TAI64NA label refers to one attosecond of real time;
see
.B http://pobox.com/~djb/proto/tai64.txt
for more information.
The integer in the
.B struct taia
is 10^18 times the second count,
plus 10^9 times the nanosecond count,
plus the attosecond count.

A
.B struct taia
variable may also be used to store
the numerical difference between two TAI64NA labels.
.SH ARITHMETIC
.B taia_approx
returns a double-precision approximation to
.IR t /10^18.
The result of
.B taia_approx
is always nonnegative.

.B taia_tai
places into
.I sec
the integer part of
.IR t /10^18.

.B taia_frac
returns a double-precision approximation to
the fraction part of
.IR t /10^18.
The result of
.B taia_frac
is always nonnegative.

.B taia_less
returns 1 if
.I a
is smaller than
.IR b ,
0 otherwise.

.B taia_add
adds
.I a
and
.I b
modulo 2^64x10^18
and puts the result into
.IR t .
The inputs and outputs may overlap.

.B taia_sub
subtracts
.I b
from
.I a
modulo 2^64x10^18
and puts the result into
.IR t .
The inputs and outputs may overlap.

.B taia_half
divides
.I a
by 2, rounding down,
and puts the result into
.IR t .
The input and output may overlap.
.SH "FORMATTING"
.B taia_fmtfrac
prints the remainder of
.IR t /10^18,
padded to exactly 18 digits,
into the character buffer
.IR s ,
without a terminating NUL.
It returns 18, the number of characters written.
.I s
may be zero;
then
.B taia_fmtfrac
returns 18 without printing anything.

The macro
.B TAIA_FMTFRAC
is defined as 19;
this is enough space for the output of
.B taia_fmtfrac
and a terminating NUL.
.SH "SEE ALSO"
taia_now(3),
taia_pack(3),
tai(3)