1.\" Copyright (c) 2002-2004 Tim J. Robbins. All rights reserved. 2.\" Copyright (c) 1993 3.\" The Regents of the University of California. All rights reserved. 4.\" 5.\" This code is derived from software contributed to Berkeley by 6.\" Donn Seeley of BSDI. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.Dd September 9, 2019 33.Dt MULTIBYTE 3 34.Os 35.Sh NAME 36.Nm multibyte 37.Nd multibyte and wide character manipulation functions 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In limits.h 42.In stdlib.h 43.In wchar.h 44.Sh DESCRIPTION 45The basic elements of some written natural languages, such as Chinese, 46cannot be represented uniquely with single C 47.Vt char Ns s . 48The C standard supports two different ways of dealing with 49extended natural language encodings: 50wide characters and 51multibyte characters. 52Wide characters are an internal representation 53which allows each basic element to map 54to a single object of type 55.Vt wchar_t . 56Multibyte characters are used for input and output 57and code each basic element as a sequence of C 58.Vt char Ns s . 59Individual basic elements may map into one or more 60(up to 61.Dv MB_LEN_MAX ) 62bytes in a multibyte character. 63.Pp 64The current locale 65.Pq Xr setlocale 3 66governs the interpretation of wide and multibyte characters. 67The locale category 68.Dv LC_CTYPE 69specifically controls this interpretation. 70The 71.Vt wchar_t 72type is wide enough to hold the largest value 73in the wide character representations for all locales. 74.Pp 75Multibyte strings may contain 76.Sq shift 77indicators to switch to and from 78particular modes within the given representation. 79If explicit bytes are used to signal shifting, 80these are not recognized as separate characters 81but are lumped with a neighboring character. 82There is always a distinguished 83.Sq initial 84shift state. 85Some functions (e.g., 86.Xr mblen 3 , 87.Xr mbtowc 3 88and 89.Xr wctomb 3 ) 90maintain static shift state internally, whereas 91others store it in an 92.Vt mbstate_t 93object passed by the caller. 94Shift states are undefined after a call to 95.Xr setlocale 3 96with the 97.Dv LC_CTYPE 98or 99.Dv LC_ALL 100categories. 101.Pp 102For convenience in processing, 103the wide character with value 0 104(the null wide character) 105is recognized as the wide character string terminator, 106and the character with value 0 107(the null byte) 108is recognized as the multibyte character string terminator. 109Null bytes are not permitted within multibyte characters. 110.Pp 111The C library provides the following functions for dealing with 112multibyte characters: 113.Bl -column "Description" 114.It Sy "Function Description" 115.It Xr mblen 3 Ta "get number of bytes in a character" 116.It Xr mbrlen 3 Ta "get number of bytes in a character (restartable)" 117.It Xr mbrtowc 3 Ta "convert a character to a wide-character code (restartable)" 118.It Xr mbsrtowcs 3 Ta "convert a character string to a wide-character string (restartable)" 119.It Xr mbstowcs 3 Ta "convert a character string to a wide-character string" 120.It Xr mbtowc 3 Ta "convert a character to a wide-character code" 121.It Xr wcrtomb 3 Ta "convert a wide-character code to a character (restartable)" 122.It Xr wcstombs 3 Ta "convert a wide-character string to a character string" 123.It Xr wcsrtombs 3 Ta "convert a wide-character string to a character string (restartable)" 124.It Xr wctomb 3 Ta "convert a wide-character code to a character" 125.El 126.Sh SEE ALSO 127.Xr localedef 1 , 128.Xr setlocale 3 , 129.Xr stdio 3 , 130.Xr big5 5 , 131.Xr euc 5 , 132.Xr gb18030 5 , 133.Xr gb2312 5 , 134.Xr gbk 5 , 135.Xr mskanji 5 , 136.Xr utf8 5 137.Sh STANDARDS 138These functions conform to 139.St -isoC-99 . 140