.\" Copyright (c) Bruno Haible <haible@clisp.cons.org>
.\"
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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
.\"   ISO/IEC 9899:1999
.\"
.TH MBSTOWCS 3  2011-09-28 "GNU" "Linux Programmer's Manual"
.SH NAME
mbstowcs \- convert a multibyte string to a wide-character string
.SH SYNOPSIS
.nf
.B #include <stdlib.h>
.sp
.BI "size_t mbstowcs(wchar_t *" dest ", const char *" src ", size_t " n );
.fi
.SH DESCRIPTION
If
.I dest
is not a NULL pointer,
the
.BR mbstowcs ()
function converts the
multibyte string
.I src
to a wide-character string starting at
.IR dest .
At most
.I n
wide characters are written to
.IR dest .
The conversion starts
in the initial state.
The conversion can stop for three reasons:
.IP 1. 3
An invalid multibyte sequence has been encountered.
In this case
.I (size_t)\ \-1
is returned.
.IP 2.
.I n
non-L\(aq\\0\(aq wide characters have been stored at
.IR dest .
In this
case the number of wide characters written to
.I dest
is returned, but the
shift state at this point is lost.
.IP 3.
The multibyte string has been completely converted, including the
terminating null wide character (\(aq\\0\(aq).
In this case the number of wide characters written to
.IR dest ,
excluding the terminating null wide character, is returned.
.PP
The programmer must ensure that there is room for at least
.I n
wide
characters at
.IR dest .
.PP
If
.IR dest
is NULL,
.I n
is ignored, and the conversion proceeds as
above, except that the converted wide characters are not written out to memory,
and that no length limit exists.
.PP
In order to avoid the case 2 above, the programmer should make sure
.I n
is
greater or equal to
.IR "mbstowcs(NULL,src,0)+1" .
.SH RETURN VALUE
The
.BR mbstowcs ()
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.
.SH CONFORMING TO
C99.
.SH NOTES
The behavior of
.BR mbstowcs ()
depends on the
.B LC_CTYPE
category of the
current locale.
.PP
The function
.BR mbsrtowcs (3)
provides a better interface to the same
functionality.
.SH SEE ALSO
.BR mbsrtowcs (3),
.BR wcstombs (3)