'\" t
.\" Copyright (c) Bruno Haible <haible@clisp.cons.org>
.\"
.\" SPDX-License-Identifier: GPL-2.0-or-later
.\"
.\" References consulted:
.\"   GNU glibc-2 source code and manual
.\"   Dinkumware C library reference http://www.dinkumware.com/
.\"   OpenGroup's Single UNIX specification http://www.UNIX-systems.org/online.html
.\"   ISO/IEC 9899:1999
.\"
.TH mbrlen 3 2023-03-30 "Linux man-pages 6.04"
.SH NAME
mbrlen \- determine number of bytes in next multibyte character
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.B #include <wchar.h>
.PP
.BI "size_t mbrlen(const char " s "[restrict ." n "], size_t " n ,
.BI "              mbstate_t *restrict " ps );
.fi
.SH DESCRIPTION
The
.BR mbrlen ()
function inspects at most
.I n
bytes of the multibyte
string starting at
.I s
and extracts the next complete multibyte character.
It updates the shift state
.IR *ps .
If the multibyte character is not the
null wide character, it returns the number of bytes that were consumed from
.IR s .
If the multibyte character is the null wide character, it resets the
shift state
.I *ps
to the initial state and returns 0.
.PP
If the
.I n
bytes starting at
.I s
do not contain a complete multibyte
character,
.BR mbrlen ()
returns
.IR "(size_t)\ \-2" .
This can happen even if
.I n
>=
.IR MB_CUR_MAX ,
if the multibyte string contains redundant shift
sequences.
.PP
If the multibyte string starting at
.I s
contains an invalid multibyte
sequence before the next complete character,
.BR mbrlen ()
returns
.I (size_t)\ \-1
and sets
.I errno
to
.BR EILSEQ .
In this case,
the effects on
.I *ps
are undefined.
.PP
If
.I ps
is NULL, a static anonymous state known only to the
.BR mbrlen ()
function is used instead.
.SH RETURN VALUE
The
.BR mbrlen ()
function returns the number of bytes
parsed from the multibyte
sequence starting at
.IR s ,
if a non-null wide character was recognized.
It returns 0, if a null wide character was recognized.
It returns
.I "(size_t)\ \-1"
and sets
.I errno
to
.BR EILSEQ ,
if an invalid multibyte sequence was
encountered.
It returns
.I (size_t)\ \-2
if it couldn't parse a complete multibyte
character, meaning that
.I n
should be increased.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.BR mbrlen ()
T}	Thread safety	MT-Unsafe race:mbrlen/!ps
.TE
.hy
.ad
.sp 1
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
POSIX.1-2001, C99.
.SH NOTES
The behavior of
.BR mbrlen ()
depends on the
.B LC_CTYPE
category of the
current locale.
.SH SEE ALSO
.BR mbrtowc (3)