NAME
Q_INI
, Q_NCBITS
,
Q_BT
, Q_TC
,
Q_NTBITS
, Q_NFCBITS
,
Q_MAXNFBITS
, Q_NFBITS
,
Q_NIBITS
, Q_RPSHFT
,
Q_ABS
, Q_MAXSTRLEN
,
Q_TOSTR
, Q_SHL
,
Q_SHR
, Q_DEBUG
—
fixed-point math miscellaneous
functions/variables
SYNOPSIS
#include
<sys/qmath.h>
QTYPE
Q_INI
(QTYPE
*q, ITYPE iv,
ITYPE dfv,
int rpshft);
Q_NCBITS
__typeof(q)
Q_BT
(QTYPE
q);
ITYPE
Q_TC
(QTYPE
q, ITYPE v);
uint32_t
Q_NTBITS
(QTYPE
q);
uint32_t
Q_NFCBITS
(QTYPE
q);
uint32_t
Q_MAXNFBITS
(QTYPE
q);
uint32_t
Q_NFBITS
(QTYPE
q);
uint32_t
Q_NIBITS
(QTYPE
q);
uint32_t
Q_RPSHFT
(QTYPE
q);
NTYPE
Q_ABS
(NTYPE
n);
uint32_t
Q_MAXSTRLEN
(QTYPE
q, int base);
char *
Q_TOSTR
(QTYPE
q, int prec,
int base,
char *s,
int slen);
ITYPE
Q_SHL
(QTYPE
q, ITYPE iv);
ITYPE
Q_SHR
(QTYPE
q, ITYPE iv);
char *, ...
Q_DEBUG
(QTYPE
q, char *prefmt,
char *postfmt,
incfmt);
ITYPE
Q_DFV2BFV
(ITYPE
dfv, int
nfbits);
DESCRIPTION
Q_INI
()
initialises a Q number with the supplied integral value
iv and decimal fractional value
dfv, with appropriate control bits based on the
requested radix shift point rpshft.
dfv must be passed as a preprocessor literal to preserve
leading zeroes.
The Q_NCBITS
defined constant specifies
the number of reserved control bits, currently 3.
Q_NTBITS
(),
Q_NFCBITS
(),
Q_MAXNFBITS
(),
Q_NFBITS
()
and
Q_NIBITS
()
return the q-specific count of total, control-encoded
fractional, maximum fractional, effective fractional, and integer bits
applicable to q respectively.
Q_BT
()
returns the C data type of q, while
Q_TC
()
returns v type casted to the C data type of
q.
Q_RPSHFT
()
returns the bit position of q's binary radix point
relative to bit zero.
Q_ABS
()
returns the absolute value of any standard numeric type (that uses the MSB
as a sign bit, but not Q numbers) passed in as n. The
function is signed/unsigned type safe.
Q_SHL
()
and
Q_SHR
()
return the integral value v left or right shifted by
the appropriate amount for q.
Q_MAXSTRLEN
()
calculates the maximum number of characters that may be required to render
the C-string representation of q with numeric base
base.
Q_TOSTR
()
renders the C-string representation of q with numeric
base base and fractional precision
prec into s which has an
available capacity of slen characters.
base must be in range [2,16]. Specifying
prec as -1 renders the number's fractional component
with maximum precision. If slen is greater than zero
but insufficient to hold the complete C-string, the '\0' C-string terminator
will be written to *s, thereby returning a zero length
C-string.
Q_DEBUG
()
returns a format string and associated data suitable for printf-like
rendering of debugging information pertaining to q. If
either prefmt and/or postfmt are
specified, they are prepended and appended to the resulting format string
respectively. The incfmt boolean specifies whether to
include (true) or exclude
(false) the raw format string itself in the debugging
output.
Q_DFV2BFV
()
converts decimal fractional value dfv to its
binary-encoded representation with nfbits of binary
precision. dfv must be passed as a preprocessor
literal to preserve leading zeroes. The returned value can be used to set a
Q number's fractional bits, for example using
Q_SFVAL
().
All of those functions operate on the following data types: s8q_t, u8q_t, s16q_t, u16q_t, s32q_t, u32q_t, s64q_t, and u64q_t, which are referred to generically as QTYPE. The ITYPE refers to the stdint(7) integer types. NTYPE is used to refer to any numeric type and is therefore a superset of QTYPE and ITYPE.
For more details, see qmath(3).
RETURN VALUES
Q_INI
() returns the initialised Q number
which can be used to chain initialise additional Q numbers.
Q_TOSTR
() returns a pointer to the '\0'
C-string terminator appended to s after the rendered
numeric data, or NULL on buffer overflow.
Q_DFV2BFV
() returns the binary-encoded
representation of decimal fractional value dfv with
nfbits of binary precision.
SEE ALSO
HISTORY
The qmath(3) functions first appeared in FreeBSD 13.0.
AUTHORS
The qmath(3) functions and this manual page were written by Lawrence Stewart <lstewart@FreeBSD.org> and sponsored by Netflix, Inc.