.\"
.\" Copyright (c) 2026 Ka Ho Ng
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd July 12, 2026
.Dt SBINTIME 9
.Os
.Sh NAME
.Nm sbintime_t ,
.Nm sbintime_getsec ,
.Nm bttosbt ,
.Nm sbttobt ,
.Nm sbttons ,
.Nm nstosbt ,
.Nm sbttous ,
.Nm ustosbt ,
.Nm sbttoms ,
.Nm mstosbt ,
.Nm sbttots ,
.Nm tstosbt ,
.Nm sbttotv ,
.Nm tvtosbt
.Nd Q32.32 fixed point representation of time
.Sh SYNOPSIS
.In sys/types.h
.In sys/time.h
.Vt typedef __int64_t __sbintime_t ;
.Vt typedef __sbintime_t sbintime_t ;
.Fd #define SBT_1S ((sbintime_t)1 << 32)
.Fd #define SBT_1M (SBT_1S * 60)
.Fd #define SBT_1MS (SBT_1S / 1000)
.Fd #define SBT_1US (SBT_1S / 1000000)
.Fd #define SBT_1NS (SBT_1S / 1000000000)
.Ft int
.Fn sbintime_getsec "sbintime_t sbt"
.Ft sbintime_t
.Fn bttosbt "const struct bintime bt"
.Ft struct bintime
.Fn sbttobt "sbintime_t sbt"
.Ft int64_t
.Fn sbttons "sbintime_t sbt"
.Ft sbintime_t
.Fn nstosbt "int64_t ns"
.Ft int64_t
.Fn sbttous "sbintime_t sbt"
.Ft sbintime_t
.Fn ustosbt "int64_t us"
.Ft int64_t
.Fn sbttoms "sbintime_t sbt"
.Ft sbintime_t
.Fn mstosbt "int64_t ms"
.Ft struct timespec
.Fn sbttots "sbintime_t sbt"
.Ft sbintime_t
.Fn tstosbt "struct timespec ts"
.Ft struct timeval
.Fn sbttotv "sbintime_t sbt"
.Ft sbintime_t
.Fn tvtosbt "struct timeval tv"
.Sh DESCRIPTION
The
.Vt sbintime_t
type is a Q32.32 fixed point representation of time.
The high 32-bit integral bits specify the number of seconds,
and the low 32-bit fractional bits specify the sub-second portion.
Since the lower 32 bits are counting with a base unit of 1/2^32 seconds,
.Ql (sbintime_t)0x1
is just under 250 picoseconds.
.Pp
All of the conversion functions are designed to do the conversion without large
truncation errors that are possible with naive math.
.\" Begin of helper functions subsection
.Bl -tag -width indent
.It Fn sbintime_getsec sbt
Return the whole number of seconds from a
.Vt sbintime_t
specified by the
.Fa sbt
argument.
.It Fn bttosbt bt
Convert a
.Vt struct bintime
specified by the
.Fa bt
argument to a
.Vt sbintime_t .
.It Fn sbttobt sbt
Convert a
.Vt sbintime_t
specified by the
.Fa sbt
argument to a
.Vt "struct bintime" .
.It Fn sbttons sbt
Convert a
.Vt sbintime_t
specified by the
.Fa sbt
argument to the number of nanoseconds.
.It Fn nstosbt ns
Convert the number of nanoseconds specified by the
.Fa ns
argument to a
.Vt sbintime_t .
.It Fn sbttous sbt
Convert a
.Vt sbintime_t
specified by the
.Fa sbt
argument to the number of microseconds.
.It Fn ustosbt us
Convert the number of microseconds specified by the
.Fa us
argument to a
.Vt sbintime_t .
.It Fn sbttoms sbt
Convert a
.Vt sbintime_t
specified by the
.Fa sbt
argument to the number of milliseconds.
.It Fn mstosbt ms
Convert the number of milliseconds specified by the
.Fa ms
argument to a
.Vt sbintime_t .
.It Fn sbttots sbt
Convert a
.Vt sbintime_t
specified by the
.Fa sbt
argument to a
.Vt "struct timespec" .
.It Fn tstosbt ts
Convert a
.Vt "struct timespec"
specified by the
.Fa ts
argument to a
.Vt sbintime_t .
.It Fn sbttotv sbt
Convert a
.Vt sbintime_t
specified by the
.Fa sbt
argument to a
.Vt "struct timeval" .
.It Fn tvtosbt tv
Convert a
.Vt "struct timeval"
specified by the
.Fa tv
argument to a
.Vt sbintime_t .
.El
.\" End of helper functions subsection
.Sh SEE ALSO
.Xr bintime 9 ,
.Xr callout 9 ,
.Xr tvtohz 9
.Sh HISTORY
The
.Nm sbintime_t
type and most of the helper functions first appeared in
.Fx 10.0 .
The Xstosbt functions first appeared in
.Fx 12.0 .
.Sh AUTHORS
This manual page was written by
.An Ka Ho Ng Aq Mt khng@FreeBSD.org .