Q_INI(3)               FreeBSD Library Functions Manual               Q_INI(3)

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
     errno(2), qmath(3), stdint(7)

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.

FreeBSD 13.1-RELEASE-p6          July 8, 2018          FreeBSD 13.1-RELEASE-p6