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.\" @(#)multibyte.3 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD$ 34.\" 35.Dd September 9, 2019 36.Dt MULTIBYTE 3 37.Os 38.Sh NAME 39.Nm multibyte 40.Nd multibyte and wide character manipulation functions 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In limits.h 45.In stdlib.h 46.In wchar.h 47.Sh DESCRIPTION 48The basic elements of some written natural languages, such as Chinese, 49cannot be represented uniquely with single C 50.Vt char Ns s . 51The C standard supports two different ways of dealing with 52extended natural language encodings: 53wide characters and 54multibyte characters. 55Wide characters are an internal representation 56which allows each basic element to map 57to a single object of type 58.Vt wchar_t . 59Multibyte characters are used for input and output 60and code each basic element as a sequence of C 61.Vt char Ns s . 62Individual basic elements may map into one or more 63(up to 64.Dv MB_LEN_MAX ) 65bytes in a multibyte character. 66.Pp 67The current locale 68.Pq Xr setlocale 3 69governs the interpretation of wide and multibyte characters. 70The locale category 71.Dv LC_CTYPE 72specifically controls this interpretation. 73The 74.Vt wchar_t 75type is wide enough to hold the largest value 76in the wide character representations for all locales. 77.Pp 78Multibyte strings may contain 79.Sq shift 80indicators to switch to and from 81particular modes within the given representation. 82If explicit bytes are used to signal shifting, 83these are not recognized as separate characters 84but are lumped with a neighboring character. 85There is always a distinguished 86.Sq initial 87shift state. 88Some functions (e.g., 89.Xr mblen 3 , 90.Xr mbtowc 3 91and 92.Xr wctomb 3 ) 93maintain static shift state internally, whereas 94others store it in an 95.Vt mbstate_t 96object passed by the caller. 97Shift states are undefined after a call to 98.Xr setlocale 3 99with the 100.Dv LC_CTYPE 101or 102.Dv LC_ALL 103categories. 104.Pp 105For convenience in processing, 106the wide character with value 0 107(the null wide character) 108is recognized as the wide character string terminator, 109and the character with value 0 110(the null byte) 111is recognized as the multibyte character string terminator. 112Null bytes are not permitted within multibyte characters. 113.Pp 114The C library provides the following functions for dealing with 115multibyte characters: 116.Bl -column "Description" 117.It Sy "Function Description" 118.It Xr mblen 3 Ta "get number of bytes in a character" 119.It Xr mbrlen 3 Ta "get number of bytes in a character (restartable)" 120.It Xr mbrtowc 3 Ta "convert a character to a wide-character code (restartable)" 121.It Xr mbsrtowcs 3 Ta "convert a character string to a wide-character string (restartable)" 122.It Xr mbstowcs 3 Ta "convert a character string to a wide-character string" 123.It Xr mbtowc 3 Ta "convert a character to a wide-character code" 124.It Xr wcrtomb 3 Ta "convert a wide-character code to a character (restartable)" 125.It Xr wcstombs 3 Ta "convert a wide-character string to a character string" 126.It Xr wcsrtombs 3 Ta "convert a wide-character string to a character string (restartable)" 127.It Xr wctomb 3 Ta "convert a wide-character code to a character" 128.El 129.Sh SEE ALSO 130.Xr localedef 1 , 131.Xr setlocale 3 , 132.Xr stdio 3 , 133.Xr big5 5 , 134.Xr euc 5 , 135.Xr gb18030 5 , 136.Xr gb2312 5 , 137.Xr gbk 5 , 138.Xr mskanji 5 , 139.Xr utf8 5 140.Sh STANDARDS 141These functions conform to 142.St -isoC-99 . 143