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	1	.\" Copyright (c) 2002-2004 Tim J. Robbins
	2	.\" All rights reserved.
	3	.\"
	4	.\" Redistribution and use in source and binary forms, with or without
	5	.\" modification, are permitted provided that the following conditions
	6	.\" are met:
	7	.\" 1. Redistributions of source code must retain the above copyright
	8	.\" notice, this list of conditions and the following disclaimer.
	9	.\" 2. Redistributions in binary form must reproduce the above copyright
	10	.\" notice, this list of conditions and the following disclaimer in the
	11	.\" documentation and/or other materials provided with the distribution.
	12	.\"
	13	.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
	14	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	15	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	16	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
	17	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	18	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	19	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	20	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	21	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	22	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	23	.\" SUCH DAMAGE.
	24	.\"
	25	.\" $FreeBSD: src/lib/libc/locale/mbrtowc.3,v 1.5 2004/06/30 19:32:41 ru Exp $
	26	.\"
	27	.Dd April 8, 2004
	28	.Dt MBRTOWC 3
	29	.Os
	30	.Sh NAME
	31	.Nm mbrtowc ,
	32	.Nm mbrtowc_l
	33	.Nd "convert a character to a wide-character code (restartable)"
	34	.Sh LIBRARY
	35	.Lb libc
	36	.Sh SYNOPSIS
	37	.In wchar.h
	38	.Ft size_t
	39	.Fo mbrtowc
	40	.Fa "wchar_t *restrict pwc"
	41	.Fa "const char *restrict s"
	42	.Fa "size_t n"
	43	.Fa "mbstate_t *restrict ps"
	44	.Fc
	45	.In wchar.h
	46	.In xlocale.h
	47	.Ft size_t
	48	.Fo mbrtowc_l
	49	.Fa "wchar_t *restrict pwc"
	50	.Fa "const char *restrict s"
	51	.Fa "size_t n"
	52	.Fa "mbstate_t *restrict ps"
	53	.Fa "locale_t loc"
	54	.Fc
	55	.Sh DESCRIPTION
	56	The
	57	.Fn mbrtowc
	58	function inspects at most
	59	.Fa n
	60	bytes, pointed to by
	61	.Fa s ,
	62	to determine the number of bytes needed to complete the next multibyte
	63	character.
	64	If a character can be completed, and
	65	.Fa pwc
	66	is not
	67	.Dv NULL ,
	68	the wide character which is represented by
	69	.Fa s
	70	is stored in the
	71	.Vt wchar_t
	72	it points to.
	73	.Pp
	74	If
	75	.Fa s
	76	is
	77	.Dv NULL ,
	78	.Fn mbrtowc
	79	behaves as if
	80	.Fa pwc
	81	were
	82	.Dv NULL ,
	83	.Fa s
	84	were an empty string
	85	.Pq Qq ,
	86	and
	87	.Fa n
	88	were 1.
	89	.Pp
	90	The
	91	.Vt mbstate_t
	92	argument,
	93	.Fa ps ,
	94	is used to keep track of the shift state.
	95	If it is
	96	.Dv NULL ,
	97	.Fn mbrtowc
	98	uses an internal, static
	99	.Vt mbstate_t
	100	object, which is initialized to the initial conversion state
	101	at program startup.
	102	.Pp
	103	While the
	104	.Fn mbrtowc
	105	function uses the current locale, the
	106	.Fn mbrtowc_l
	107	function may be passed a locale directly. See
	108	.Xr xlocale 3
	109	for more information.
	110	.Sh RETURN VALUES
	111	The
	112	.Fn mbrtowc
	113	functions returns:
	114	.Bl -tag -width indent
	115	.It 0
	116	The next
	117	.Fa n
	118	or fewer bytes
	119	represent the null wide character
	120	.Pq Li "L'\e0'" .
	121	.It >0
	122	The next
	123	.Fa n
	124	or fewer bytes
	125	represent a valid character,
	126	.Fn mbrtowc
	127	returns the number of bytes used to complete the multibyte character.
	128	.It Po Vt size_t Pc Ns \-2
	129	The next
	130	.Fa n
	131	contribute to, but do not complete, a valid multibyte character sequence,
	132	and all
	133	.Fa n
	134	bytes have been processed.
	135	.It Po Vt size_t Pc Ns \-1
	136	An encoding error has occurred.
	137	The next
	138	.Fa n
	139	or fewer bytes do not contribute to a valid multibyte character.
	140	.El
	141	.Sh ERRORS
	142	The
	143	.Fn mbrtowc
	144	function will fail if:
	145	.Bl -tag -width Er
	146	.It Bq Er EILSEQ
	147	An invalid multibyte sequence was detected.
	148	.It Bq Er EINVAL
	149	The conversion state is invalid.
	150	.El
	151	.Sh SEE ALSO
	152	.Xr mbtowc 3 ,
	153	.Xr multibyte 3 ,
	154	.Xr setlocale 3 ,
	155	.Xr wcrtomb 3 ,
	156	.Xr xlocale 3
	157	.Sh STANDARDS
	158	The
	159	.Fn mbrtowc
	160	function conforms to
	161	.St -isoC-99 .