NAME
multibyte —
multibyte and wide character
manipulation functions
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
DESCRIPTION
The basic elements of some written natural languages, such as
Chinese, cannot be represented uniquely with single C
chars. The C standard supports two different ways of
dealing with extended natural language encodings: wide characters and
multibyte characters. Wide characters are an internal representation which
allows each basic element to map to a single object of type
wchar_t. Multibyte characters are used for input and
output and code each basic element as a sequence of C
chars. Individual basic elements may map into one or
more (up to MB_LEN_MAX) bytes in a multibyte
character.
The current locale
(setlocale(3)) governs the interpretation of wide and multibyte
characters. The locale category LC_CTYPE
specifically controls this interpretation. The wchar_t
type is wide enough to hold the largest value in the wide character
representations for all locales.
Multibyte strings may contain ‘shift’ indicators to
switch to and from particular modes within the given representation. If
explicit bytes are used to signal shifting, these are not recognized as
separate characters but are lumped with a neighboring character. There is
always a distinguished ‘initial’ shift state. Some functions
(e.g., mblen(3), mbtowc(3) and wctomb(3)) maintain static shift state internally, whereas
others store it in an mbstate_t object passed by the
caller. Shift states are undefined after a call to
setlocale(3) with the LC_CTYPE or
LC_ALL categories.
For convenience in processing, the wide character with value 0 (the null wide character) is recognized as the wide character string terminator, and the character with value 0 (the null byte) is recognized as the multibyte character string terminator. Null bytes are not permitted within multibyte characters.
The C library provides the following functions for dealing with multibyte characters:
| Function | Description |
| mblen(3) | get number of bytes in a character |
| mbrlen(3) | get number of bytes in a character (restartable) |
| mbrtowc(3) | convert a character to a wide-character code (restartable) |
| mbsrtowcs(3) | convert a character string to a wide-character string (restartable) |
| mbstowcs(3) | convert a character string to a wide-character string |
| mbtowc(3) | convert a character to a wide-character code |
| wcrtomb(3) | convert a wide-character code to a character (restartable) |
| wcstombs(3) | convert a wide-character string to a character string |
| wcsrtombs(3) | convert a wide-character string to a character string (restartable) |
| wctomb(3) | convert a wide-character code to a character |
SEE ALSO
mklocale(1), setlocale(3), stdio(3), big5(5), euc(5), gb18030(5), gb2312(5), gbk(5), mskanji(5), utf8(5)
STANDARDS
These functions conform to ISO/IEC 9899:1999 (“ISO C99”).