1.\" $OpenBSD: mbtowc.3,v 1.3 2010/11/20 18:23:19 stsp Exp $ 2.\" $NetBSD: mbtowc.3,v 1.5 2003/09/08 17:54:31 wiz Exp $ 3.\" 4.\" Copyright (c)2002 Citrus Project, 5.\" All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.Dd $Mdocdate: November 20 2010 $ 29.Dt MBTOWC 3 30.Os 31.\" ---------------------------------------------------------------------- 32.Sh NAME 33.Nm mbtowc 34.Nd converts a multibyte character to a wide character 35.\" ---------------------------------------------------------------------- 36.Sh SYNOPSIS 37.Fd #include <stdlib.h> 38.Ft int 39.Fn mbtowc "wchar_t * restrict pwc" "const char * restrict s" "size_t n" 40.Sh DESCRIPTION 41The 42.Fn mbtowc 43usually converts the multibyte character pointed to by 44.Fa s 45to a wide character, and stores it in the wchar_t object pointed to by 46.Fa pwc 47if 48.Fa pwc 49is non-null and 50.Fa s 51points to a valid character. 52This function may inspect at most n bytes of the array beginning from 53.Fa s . 54.Pp 55In state-dependent encodings, 56.Fa s 57may point to the special sequence bytes to change the shift-state. 58Although such sequence bytes correspond to no individual 59wide-character code, 60.Fn mbtowc 61changes its own state by the sequence bytes and treats them 62as if they are a part of the subsequence multibyte character. 63.Pp 64Unlike 65.Xr mbrtowc 3 , 66the first 67.Fa n 68bytes pointed to by 69.Fa s 70need to form an entire multibyte character. 71Otherwise, this function causes an error. 72.Pp 73Calling any other functions in 74.Em libc 75never change the internal 76state of the 77.Fn mbtowc , 78except for calling 79.Xr setlocale 3 80with the 81.Dv LC_CTYPE 82category changed to that of the current locale. 83Such 84.Xr setlocale 3 85calls cause the internal state of this function to be indeterminate. 86.Pp 87The behaviour of 88.Fn mbtowc 89is affected by the 90.Dv LC_CTYPE 91category of the current locale. 92.Pp 93These are the special cases: 94.Bl -tag -width 012345678901 95.It s == NULL 96.Fn mbtowc 97initializes its own internal state to an initial state, and 98determines whether the current encoding is state-dependent. 99This function returns 0 if the encoding is state-independent, 100otherwise non-zero. 101In this case, 102.Fa pwc 103is completely ignored. 104.It pwc == NULL 105.Fn mbtowc 106executes the conversion as if 107.Fa pwc 108is non-null, but a result of the conversion is discarded. 109.It n == 0 110In this case, 111the first 112.Fa n 113bytes of the array pointed to by 114.Fa s 115never form a complete character. 116Thus, the 117.Fn mbtowc 118always fails. 119.El 120.\" ---------------------------------------------------------------------- 121.Sh RETURN VALUES 122Normally, 123.Fn mbtowc 124returns: 125.Bl -tag -width 012345678901 126.It 0 127.Fa s 128points to a null byte 129.Pq Sq \e0 . 130.It positive 131Number of bytes for the valid multibyte character pointed to by 132.Fa s . 133There are no cases where the value returned is greater than 134the value of the 135.Dv MB_CUR_MAX 136macro. 137.It -1 138.Fa s 139points to an invalid or an incomplete multibyte character. 140The 141.Fn mbtowc 142also sets errno to indicate the error. 143.El 144.Pp 145When 146.Fa s 147is equal to NULL, 148.Fn mbtowc 149returns: 150.Bl -tag -width 0123456789 151.It 0 152The current encoding is state-independent. 153.It non-zero 154The current encoding is state-dependent. 155.El 156.\" ---------------------------------------------------------------------- 157.Sh ERRORS 158.Fn mbtowc 159may cause an error in the following cases: 160.Bl -tag -width Er 161.It Bq Er EILSEQ 162.Fa s 163points to an invalid or incomplete multibyte character. 164.El 165.\" ---------------------------------------------------------------------- 166.Sh SEE ALSO 167.Xr mblen 3 , 168.Xr mbrtowc 3 , 169.Xr setlocale 3 170.\" ---------------------------------------------------------------------- 171.Sh STANDARDS 172The 173.Fn mbtowc 174function conforms to 175.St -ansiC . 176The restrict qualifier is added at 177.\" .St -isoC99 . 178ISO/IEC 9899/1999 179.Pq Dq ISO C99 . 180.Sh CAVEATS 181On error, callers of 182.Fn mbtowc 183cannot tell whether the multibyte character was invalid or incomplete. 184To treat incomplete data differently from invalid data the 185.Xr mbrtowc 3 186function can be used instead. 187