260 lines
6.0 KiB
Groff
260 lines
6.0 KiB
Groff
.\"
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.\" Copyright (c) 2018 Netflix, Inc.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions, and the following disclaimer,
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.\" without modification, immediately at the beginning of the file.
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.\" 2. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
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.\" ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.Dd July 8, 2018
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.Dt Q_INI 3
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.Os
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.Sh NAME
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.Nm Q_INI ,
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.Nm Q_NCBITS ,
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.Nm Q_BT ,
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.Nm Q_TC ,
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.Nm Q_NTBITS ,
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.Nm Q_NFCBITS ,
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.Nm Q_MAXNFBITS ,
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.Nm Q_NFBITS ,
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.Nm Q_NIBITS ,
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.Nm Q_RPSHFT ,
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.Nm Q_ABS ,
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.Nm Q_MAXSTRLEN ,
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.Nm Q_TOSTR ,
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.Nm Q_SHL ,
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.Nm Q_SHR ,
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.Nm Q_DEBUG
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.Nd fixed-point math miscellaneous functions/variables
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.Sh SYNOPSIS
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.In sys/qmath.h
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.Ft QTYPE
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.Fn Q_INI "QTYPE *q" "ITYPE iv" "ITYPE dfv" "int rpshft"
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.Fd Q_NCBITS
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.Ft __typeof(q)
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.Fn Q_BT "QTYPE q"
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.Ft ITYPE
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.Fn Q_TC "QTYPE q" "ITYPE v"
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.Ft uint32_t
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.Fn Q_NTBITS "QTYPE q"
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.Ft uint32_t
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.Fn Q_NFCBITS "QTYPE q"
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.Ft uint32_t
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.Fn Q_MAXNFBITS "QTYPE q"
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.Ft uint32_t
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.Fn Q_NFBITS "QTYPE q"
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.Ft uint32_t
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.Fn Q_NIBITS "QTYPE q"
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.Ft uint32_t
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.Fn Q_RPSHFT "QTYPE q"
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.Ft NTYPE
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.Fn Q_ABS "NTYPE n"
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.Ft uint32_t
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.Fn Q_MAXSTRLEN "QTYPE q" "int base"
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.Ft char *
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.Fn Q_TOSTR "QTYPE q" "int prec" "int base" "char *s" "int slen"
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.Ft ITYPE
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.Fn Q_SHL "QTYPE q" "ITYPE iv"
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.Ft ITYPE
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.Fn Q_SHR "QTYPE q" "ITYPE iv"
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.Ft char *, ...
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.Fn Q_DEBUG "QTYPE q" "char *prefmt" "char *postfmt" "incfmt"
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.Ft ITYPE
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.Fn Q_DFV2BFV "ITYPE dfv" "int nfbits"
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.Sh DESCRIPTION
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.Fn Q_INI
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initialises a Q number with the supplied integral value
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.Fa iv
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and decimal fractional value
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.Fa dfv ,
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with appropriate control bits based on the requested radix shift point
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.Fa rpshft .
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.Fa dfv
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must be passed as a preprocessor literal to preserve leading zeroes.
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.Pp
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The
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.Dv Q_NCBITS
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defined constant specifies the number of reserved control bits, currently 3.
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.Pp
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.Fn Q_NTBITS ,
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.Fn Q_NFCBITS ,
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.Fn Q_MAXNFBITS ,
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.Fn Q_NFBITS
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and
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.Fn Q_NIBITS
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return the
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.Fa q Ns -specific
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count of total, control-encoded fractional, maximum fractional, effective
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fractional, and integer bits applicable to
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.Fa q
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respectively.
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.Pp
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.Fn Q_BT
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returns the C data type of
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.Fa q ,
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while
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.Fn Q_TC
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returns
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.Fa v
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type casted to the C data type of
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.Fa q .
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.Pp
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.Fn Q_RPSHFT
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returns the bit position of
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.Fa q Ap s
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binary radix point relative to bit zero.
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.Pp
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.Fn Q_ABS
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returns the absolute value of any standard numeric type
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.Pq that uses the MSB as a sign bit, but not Q numbers
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passed in as
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.Fa n .
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The function is signed/unsigned type safe.
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.Pp
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.Fn Q_SHL
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and
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.Fn Q_SHR
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return the integral value
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.Fa v
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left or right shifted by the appropriate amount for
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.Fa q .
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.Pp
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.Fn Q_MAXSTRLEN
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calculates the maximum number of characters that may be required to render the
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C-string representation of
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.Fa q
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with numeric base
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.Fa base .
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.Pp
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.Fn Q_TOSTR
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renders the C-string representation of
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.Fa q
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with numeric base
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.Fa base
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and fractional precision
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.Fa prec
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into
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.Fa s
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which has an available capacity of
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.Fa slen
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characters.
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.Fa base
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must be in range
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.Bq 2,16 .
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Specifying
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.Fa prec
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as -1 renders the number's fractional component with maximum precision.
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If
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.Fa slen
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is greater than zero but insufficient to hold the complete C-string, the '\\0'
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C-string terminator will be written to
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.Fa *s ,
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thereby returning a zero length C-string.
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.Pp
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.Fn Q_DEBUG
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returns a format string and associated data suitable for printf-like rendering
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of debugging information pertaining to
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.Fa q .
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If either
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.Fa prefmt
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and/or
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.Fa postfmt
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are specified, they are prepended and appended to the resulting format string
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respectively.
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The
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.Fa incfmt
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boolean specifies whether to include
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.Pq Vt true
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or exclude
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.Pq Vt false
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the raw format string itself in the debugging output.
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.Pp
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.Fn Q_DFV2BFV
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converts decimal fractional value
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.Fa dfv
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to its binary-encoded representation with
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.Fa nfbits
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of binary precision.
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.Fa dfv
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must be passed as a preprocessor literal to preserve leading zeroes.
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The returned value can be used to set a Q number's fractional bits, for example
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using
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.Fn Q_SFVAL .
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.Pp
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All of those functions operate on
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the following data types:
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.Vt s8q_t ,
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.Vt u8q_t ,
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.Vt s16q_t ,
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.Vt u16q_t ,
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.Vt s32q_t ,
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.Vt u32q_t ,
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.Vt s64q_t ,
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and
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.Vt u64q_t ,
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which are referred to generically as
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.Fa QTYPE .
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The
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.Fa ITYPE
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refers to the
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.Xr stdint 7
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integer types.
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.Fa NTYPE
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is used to refer to any numeric type and is therefore a superset of
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.Fa QTYPE
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and
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.Fa ITYPE .
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.Pp
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For more details, see
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.Xr qmath 3 .
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.Sh RETURN VALUES
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.Fn Q_INI
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returns the initialised Q number which can be used to chain initialise
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additional Q numbers.
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.Pp
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.Fn Q_TOSTR
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returns a pointer to the '\\0' C-string terminator appended to
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.Fa s
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after the rendered numeric data, or NULL on buffer overflow.
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.Pp
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.Fn Q_DFV2BFV
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returns the binary-encoded representation of decimal fractional value
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.Fa dfv
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with
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.Fa nfbits
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of binary precision.
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.Sh SEE ALSO
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.Xr errno 2 ,
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.Xr qmath 3 ,
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.Xr stdint 7
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.Sh HISTORY
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The
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.Xr qmath 3
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functions first appeared in
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.Fx 13.0 .
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.Sh AUTHORS
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.An -nosplit
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The
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.Xr qmath 3
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functions and this manual page were written by
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.An Lawrence Stewart Aq Mt lstewart@FreeBSD.org
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and sponsored by Netflix, Inc.
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