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.\" Copyright (c) 2002-2004 Tim J. Robbins
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd May 21, 2013
.Dt MBRTOWC 3
.Os
.Sh NAME
.Nm mbrtowc ,
.Nm mbrtoc16 ,
.Nm mbrtoc32
.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 pc" "const char * restrict s" "size_t n"
.Fa "mbstate_t * restrict ps"
.Fc
.In uchar.h
.Ft size_t
.Fo mbrtoc16
.Fa "char16_t * restrict pc" "const char * restrict s" "size_t n"
.Fa "mbstate_t * restrict ps"
.Fc
.Ft size_t
.Fo mbrtoc32
.Fa "char32_t * restrict pc" "const char * restrict s" "size_t n"
.Fa "mbstate_t * restrict ps"
.Fc
.Sh DESCRIPTION
The
.Fn mbrtowc ,
.Fn mbrtoc16
and
.Fn mbrtoc32
functions inspect at most
.Fa n
bytes pointed to by
.Fa s
to determine the number of bytes needed to complete the next multibyte
character.
If a character can be completed, and
.Fa pc
is not
.Dv NULL ,
the wide character which is represented by
.Fa s
is stored in the
.Vt wchar_t ,
.Vt char16_t
or
.Vt char32_t
it points to.
.Pp
If
.Fa s
is
.Dv NULL ,
these functions behave as if
.Fa pc
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 ,
these functions use an internal, static
.Vt mbstate_t
object, which is initialized to the initial conversion state
at program startup.
.Pp
As a single
.Vt char16_t
is not large enough to represent certain multibyte characters, the
.Fn mbrtoc16
function may need to be invoked multiple times to convert a single
multibyte character sequence.
.Sh RETURN VALUES
The
.Fn mbrtowc ,
.Fn mbrtoc16
and
.Fn mbrtoc32
functions return:
.Bl -tag -width indent
.It 0
The next
.Fa n
or fewer bytes
represent the null wide character
.Pq Li "L'\e0'" .
.It >0
The next
.Fa n
or fewer bytes represent a valid character, these functions
return the number of bytes used to complete the multibyte character.
.It Po Vt size_t Pc Ns \-1
An encoding error has occurred.
The next
.Fa n
or fewer bytes do not contribute to a valid multibyte character.
.It Po Vt size_t Pc Ns \-2
The next
.Fa n
contribute to, but do not complete, a valid multibyte character sequence,
and all
.Fa n
bytes have been processed.
.El
.Pp
The
.Fn mbrtoc16
function also returns:
.Bl -tag -width indent
.It Po Vt size_t Pc Ns \-3
The next character resulting from a previous call has been stored.
No bytes from the input have been consumed.
.El
.Sh ERRORS
The
.Fn mbrtowc ,
.Fn mbrtoc16
and
.Fn mbrtoc32
functions will fail if:
.Bl -tag -width Er
.It Bq Er EILSEQ
An invalid multibyte sequence was detected.
.It Bq Er EINVAL
The conversion state is invalid.
.El
.Sh SEE ALSO
.Xr mbtowc 3 ,
.Xr multibyte 3 ,
.Xr setlocale 3 ,
.Xr wcrtomb 3
.Sh STANDARDS
The
.Fn mbrtowc ,
.Fn mbrtoc16
and
.Fn mbrtoc32
functions conform to
.St -isoC-2011 .