.\" 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 MBRTOWC 3  "July 25, 1999" "GNU" "Linux Programmer's Manual"
.SH NAME
mbrtowc \- convert a multibyte sequence to a wide character
.SH SYNOPSIS
.nf
.B #include <wchar.h>
.sp
.BI "size_t mbrtowc (wchar_t *" pwc ", const char *" s ", size_t " n ", mbstate_t *" ps );
.fi
.SH DESCRIPTION
The main case for this function is when \fIs\fP is not NULL and \fIpwc\fP is
not NULL. In this case, the \fBmbrtowc\fP function inspects at most \fIn\fP
bytes of the multibyte string starting at \fIs\fP, extracts the next complete
multibyte character, converts it to a wide character and stores it at
\fI*pwc\fP. It updates the shift state \fI*ps\fP. If the converted wide
character is not L'\\0', it returns the number of bytes that were consumed
from \fIs\fP. If the converted wide character is L'\\0', it resets the shift
state \fI*ps\fP to the initial state and returns 0.
.PP
If the \fIn\fP bytes starting at \fIs\fP do not contain a complete multibyte
character, \fBmbrtowc\fP returns \fI(size_t)(-2)\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, \fBmbrtowc\fP returns
\fI(size_t)(-1)\fP and sets \fBerrno\fP to \fBEILSEQ\fP. In this case,
the effects on \fI*ps\fP are undefined.
.PP
A different case is when \fIs\fP is not NULL but \fIpwc\fP is NULL. In this
case the \fBmbrtowc\fP function behaves as above, excepts that it does not
store the converted wide character in memory.
.PP
A third case is when \fIs\fP is NULL. In this case, \fIpwc\fP and \fIn\fP are
ignored. The \fBmbrtowc\fP function puts \fI*ps\fP in the initial state and
returns 0.
.PP
In all of the above cases, if \fIps\fP is a NULL pointer, a static anonymous
state only known to the mbrtowc function is used instead.
.SH "RETURN VALUE"
The \fBmbrtowc\fP function returns the number of bytes parsed from the multibyte
sequence starting at \fIs\fP, if a non-L'\\0' wide character was recognized.
It returns 0, if a L'\\0' wide character was recognized. It returns (size_t)(-1)
and sets \fBerrno\fP to \fBEILSEQ\fP, if an invalid multibyte sequence was
encountered. It returns (size_t)(-2) if it couldn't parse a complete multibyte
character, meaning that \fIn\fP should be increased.
.SH "CONFORMING TO"
ISO/ANSI C, UNIX98
.SH "SEE ALSO"
.BR mbsrtowcs (3)
.SH NOTES
The behaviour of \fBmbrtowc\fP depends on the LC_CTYPE category of the
current locale.