.\" Copyright (c) Bruno Haible <haible@clisp.cons.org>
.\"
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" the License, or (at your option) any later version.
.\"
.\" 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 MBLEN 3  "July 25, 1999" "GNU" "Linux Programmer's Manual"
.SH NAME
mblen \- determine number of bytes in next multibyte character
.SH SYNOPSIS
.nf
.B #include <stdlib.h>
.sp
.BI "int mblen (const char *" s ", size_t " n );
.fi
.SH DESCRIPTION
If \fIs\fP is not a NULL pointer, the \fBmblen\fP function inspects at most
\fIn\fP bytes of the multibyte string starting at \fIs\fP and extracts the
next complete multibyte character. It uses a static anonymous shift state only
known to the mblen function. If the multibyte character is not the null wide
character, it returns the number of bytes that were consumed from \fIs\fP. If
the multibyte character is the null wide character, it returns 0.
.PP
If the \fIn\fP bytes starting at \fIs\fP do not contain a complete multibyte
character, \fBmblen\fP returns \fI-1\fP. This can happen even if
\fIn\fP >= \fIMB_CUR_MAX\fP, if the multibyte string contains redundant shift
sequences.
.PP
If the multibyte string starting at \fIs\fP contains an invalid multibyte
sequence before the next complete character, \fBmblen\fP also returns \fI-1\fP.
.PP
If \fIs\fP is a NULL pointer, the \fBmblen\fP function
.\" The Dinkumware doc and the Single Unix specification say this, but
.\" glibc doesn't implement this.
resets the shift state, only known to this function, to the initial state, and
returns non-zero if the encoding has non-trivial shift state, or zero if the
encoding is stateless.
.SH "RETURN VALUE"
The \fBmblen\fP function returns the number of bytes parsed from the multibyte
sequence starting at \fIs\fP, if a non-null wide character was recognized.
It returns 0, if a null wide character was recognized. It returns -1, if an
invalid multibyte sequence was encountered or if it couldn't parse a complete
multibyte character.
.SH "CONFORMING TO"
ISO/ANSI C, UNIX98
.SH "SEE ALSO"
.BR mbrlen (3)
.SH NOTES
The behaviour of \fBmblen\fP depends on the LC_CTYPE category of the
current locale.
.PP
The function \fBmbrlen\fP provides a better interface to the same
functionality.