5a38af1fb8
This makes it possible to perform mathematical operations on fractional values without using floating point. It operates on Q numbers, which are integer-sized, opaque structures initialized to hold a chosen number of integer and fractional bits. For a general description of the Q number system, see the "Fixed Point Representation & Fractional Math" whitepaper[1]; for the actual API see the qmath(3) man page. This is one of dependencies for the upcoming stats(3) framework[2] that will be applied to the TCP stack in a later commit. 1. https://www.superkits.net/whitepapers/Fixed%20Point%20Representation%20&%20Fractional%20Math.pdf 2. https://reviews.freebsd.org/D20477 Reviewed by: bcr (man pages, earlier version), sef (earlier version) Discussed with: cem, dteske, imp, lstewart Sponsored By: Klara Inc, Netflix Obtained from: Netflix Differential Revision: https://reviews.freebsd.org/D20116
135 lines
3.1 KiB
Groff
135 lines
3.1 KiB
Groff
.\"
|
|
.\" Copyright (c) 2018 Netflix, Inc.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions, and the following disclaimer,
|
|
.\" without modification, immediately at the beginning of the file.
|
|
.\" 2. The name of the author may not be used to endorse or promote products
|
|
.\" derived from this software without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
|
|
.\" ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd July 8, 2018
|
|
.Dt Q_QADDI 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm Q_QADDI ,
|
|
.Nm Q_QDIVI ,
|
|
.Nm Q_QMULI ,
|
|
.Nm Q_QSUBI ,
|
|
.Nm Q_QFRACI ,
|
|
.Nm Q_QCPYVALI
|
|
.Nd fixed-point math functions which apply integers to a Q number
|
|
.Sh SYNOPSIS
|
|
.In sys/qmath.h
|
|
.Ft int
|
|
.Fn Q_QADDI "QTYPE *a" "ITYPE b"
|
|
.Ft int
|
|
.Fn Q_QDIVI "QTYPE *a" "ITYPE b"
|
|
.Ft int
|
|
.Fn Q_QMULI "QTYPE *a" "ITYPE b"
|
|
.Ft int
|
|
.Fn Q_QSUBI "QTYPE *a" "ITYPE b"
|
|
.Ft int
|
|
.Fn Q_QFRACI "QTYPE *q" "ITYPE n" "ITYPE d"
|
|
.Ft int
|
|
.Fn Q_QCPYVALI "QTYPE *q" "ITYPE i"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn Q_QADDI ,
|
|
.Fn Q_QDIVI ,
|
|
.Fn Q_QMULI
|
|
and
|
|
.Fn Q_QSUBI
|
|
functions add, divide, multiply or subtract
|
|
.Fa b
|
|
to/by/from
|
|
.Fa a
|
|
respectively, storing the result in
|
|
.Fa a .
|
|
.Pp
|
|
The
|
|
.Fn Q_QFRACI
|
|
function computes the fraction
|
|
.Fa n
|
|
divided by
|
|
.Fa d
|
|
and stores the fixed-point result in
|
|
.Fa q .
|
|
.Pp
|
|
The
|
|
.Fn Q_QCPYVALI
|
|
function overwrites
|
|
.Fa q Ap s
|
|
integer and fractional bits with the Q representation of integer value
|
|
.Fa i .
|
|
.Pp
|
|
All of those functions operate on
|
|
the following data types:
|
|
.Vt s8q_t ,
|
|
.Vt u8q_t ,
|
|
.Vt s16q_t ,
|
|
.Vt u16q_t ,
|
|
.Vt s32q_t ,
|
|
.Vt u32q_t ,
|
|
.Vt s64q_t ,
|
|
and
|
|
.Vt u64q_t ,
|
|
which are referred to generically as
|
|
.Fa QTYPE .
|
|
The
|
|
.Fa ITYPE
|
|
refers to the
|
|
.Xr stdint 7
|
|
integer types.
|
|
.Pp
|
|
For more details, see
|
|
.Xr qmath 3 .
|
|
.Sh RETURN VALUES
|
|
.Fn Q_QADDI ,
|
|
.Fn Q_QDIVI ,
|
|
.Fn Q_QMULI ,
|
|
.Fn Q_QSUBI ,
|
|
.Fn Q_QFRACI
|
|
and
|
|
.Fn Q_QCPYVALI
|
|
functions return 0 on success, or an errno on failure.
|
|
.Er EINVAL
|
|
is returned for divide-by-zero.
|
|
.Er EOVERFLOW
|
|
and
|
|
.Er ERANGE
|
|
are returned for overflow and underflow respectively.
|
|
.Sh SEE ALSO
|
|
.Xr errno 2 ,
|
|
.Xr qmath 3 ,
|
|
.Xr stdint 7
|
|
.Sh HISTORY
|
|
The
|
|
.Xr qmath 3
|
|
functions first appeared in
|
|
.Fx 13.0 .
|
|
.Sh AUTHORS
|
|
.An -nosplit
|
|
The
|
|
.Xr qmath 3
|
|
functions and this manual page were written by
|
|
.An Lawrence Stewart Aq Mt lstewart@FreeBSD.org
|
|
and sponsored by Netflix, Inc.
|