.\" Copyright (c) 2002 Tim J. Robbins
.\" All rights reserved.
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.\" $FreeBSD: src/lib/libc/locale/mbrtowc.3,v 1.3 2002/11/29 17:35:09 ru Exp $
.\"
.Dd August 15, 2002
.Dt MBRTOWC 3
.Os
.Sh NAME
.Nm mbrtowc
.Nd "convert a character to a wide-character code (restartable)"
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In wchar.h
.Ft size_t
.Fo mbrtowc
.Fa "wchar_t * restrict pwc" "const char * restrict s" "size_t n"
.Fa "mbstate_t * restrict ps"
.Fc
.Sh DESCRIPTION
The
.Fn mbrtowc
function inspects at most
.Fa n
bytes pointed to by
.Fa s
and interprets them as a multibyte character sequence
according to the current setting of
.Ev LC_CTYPE .
If
.Fa pwc
is not
.Dv NULL ,
the multibyte character which
.Fa s
represents is stored in the
.Vt wchar_t
it points to.
.Pp
If
.Fa s
is
.Dv NULL ,
.Fn mbrtowc
behaves as if
.Fa pwc
was
.Dv NULL ,
.Fa s
was an empty string
.Pq Qq
and
.Fa n
was 1.
.Pp
The
.Vt mbstate_t
argument,
.Fa ps ,
is used to keep track of the shift state.
If it is
.Dv NULL ,
.Fn mbrtowc
uses an internal, static
.Vt mbstate_t
object.
.Sh RETURN VALUES
The
.Fn mbrtowc
functions returns:
.Bl -tag -width indent
.It 0
The first
.Fa n
or fewer bytes of
.Fa s
represent the null wide character
.Pq Li "L'\e0'" .
.It >0
The first
.Fa n
or fewer bytes of
.Fa s
represent a valid character,
.Fn mbrtowc
returns the length (in bytes) of the multibyte sequence.
.It Po Vt size_t Pc Ns \-2
The first
.Fa n
bytes of
.Fa s
are an incomplete multibyte sequence.
.It Po Vt size_t Pc Ns \-1
The byte sequence pointed to by
.Fa s
is an invalid multibyte sequence.
.El
.Sh ERRORS
The
.Fn mbrtowc
function will fail if:
.Bl -tag -width Er
.\".It Bq Er EINVAL
.\"Invalid argument.
.It Bq Er EILSEQ
An invalid multibyte sequence was detected.
.El
.Sh SEE ALSO
.Xr mbtowc 3 ,
.Xr setlocale 3 ,
.Xr wcrtomb 3
.Sh STANDARDS
The
.Fn mbrtowc
function conforms to
.St -isoC-99 .
.Sh BUGS
The current implementation does not support shift states.