.\" 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.
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.\" 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
.\"
.TH MBSNRTOWCS 3  2011-10-01 "GNU" "Linux Programmer's Manual"
.SH NAME
mbsnrtowcs \- convert a multibyte string to a wide-character string
.SH SYNOPSIS
.nf
.B #include <wchar.h>
.sp
.BI "size_t mbsnrtowcs(wchar_t *" dest ", const char **" src ,
.BI "                  size_t " nms ", size_t " len ", mbstate_t *" ps );
.fi
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.BR mbsnrtowcs ():
.PD 0
.ad l
.RS 4
.TP 4
Since glibc 2.10:
_XOPEN_SOURCE\ >=\ 700 || _POSIX_C_SOURCE\ >=\ 200809L
.TP
Before glibc 2.10:
_GNU_SOURCE
.RE
.ad
.PD
.SH DESCRIPTION
The
.BR mbsnrtowcs ()
function is like the
.BR mbsrtowcs (3)
function, except that
the number of bytes to be converted, starting at \fI*src\fP, is limited to
\fInms\fP.
.PP
If \fIdest\fP is not a NULL pointer, the
.BR mbsnrtowcs ()
function converts at
most \fInms\fP bytes from the
multibyte string \fI*src\fP to a wide-character string starting at \fIdest\fP.
At most \fIlen\fP wide characters are written to \fIdest\fP.
The shift state
\fI*ps\fP is updated.
The conversion is effectively performed by repeatedly
calling
.I "mbrtowc(dest, *src, n, ps)"
where \fIn\fP is some
positive number, as long as this call succeeds, and then incrementing
\fIdest\fP by one and \fI*src\fP by the number of bytes consumed.
The
conversion can stop for three reasons:
.IP 1. 3
An invalid multibyte sequence has been encountered.
In this case \fI*src\fP
is left pointing to the invalid multibyte sequence,
.I (size_t)\ \-1
is returned,
and \fIerrno\fP is set to \fBEILSEQ\fP.
.IP 2.
The \fInms\fP limit forces a stop,
or \fIlen\fP non-L\(aq\\0\(aq wide characters
have been stored at \fIdest\fP.
In this case \fI*src\fP is left pointing to the
next multibyte sequence to be converted, and the number of wide characters
written to \fIdest\fP is returned.
.IP 3.
The multibyte string has been completely converted, including the
terminating null wide character (\(aq\\0\(aq)
(which has the side effect of bringing back \fI*ps\fP to the
initial state).
In this case \fI*src\fP is set to NULL, and the number of wide
characters written to \fIdest\fP,
excluding the terminating null wide character,
is returned.
.PP
If \fIdest\fP is NULL, \fIlen\fP is ignored, and the conversion proceeds as
above, except that the converted wide characters
are not written out to memory,
and that no destination length limit exists.
.PP
In both of the above cases, if \fIps\fP is a NULL pointer, a static anonymous
state only known to the mbsnrtowcs function is used instead.
.PP
The programmer must ensure that there is room for at least \fIlen\fP wide
characters at \fIdest\fP.
.SH "RETURN VALUE"
The
.BR mbsnrtowcs ()
function returns the number of wide characters
that make up the converted part of the wide-character string,
not including the terminating null wide character.
If an invalid multibyte sequence was
encountered,
.I (size_t)\ \-1
is returned, and \fIerrno\fP set to \fBEILSEQ\fP.
.SH "CONFORMING TO"
POSIX.1-2008.
.SH NOTES
The behavior of
.BR mbsnrtowcs ()
depends on the
.B LC_CTYPE
category of the
current locale.
.PP
Passing NULL as \fIps\fP is not multithread safe.
.SH "SEE ALSO"
.BR iconv (3),
.BR mbsrtowcs (3)
.SH COLOPHON
This page is part of release 3.44 of the Linux
.I man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.