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Null-terminated multibyte strings

A null-terminated multibyte string (NTMBS), or "multibyte string", is a sequence of nonzero bytes followed by a byte with value zero (the terminating null character).

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Each character stored in the string may occupy more than one byte. The encoding used to represent characters in a multibyte character string is locale-specific: it may be UTF-8, GB18030, EUC-JP, Shift-JIS, etc. For example, the char array {'\xe4','\xbd','\xa0','\xe5','\xa5','\xbd','\0'} is an NTMBS holding the string "你好" in UTF-8 multibyte encoding: the first three bytes encode the character 你, the next three bytes encode the character 好. The same string encoded in GB18030 is the char array {'\xc4', '\xe3', '\xba', '\xc3', '\0'}, where each of the two characters is encoded as a two-byte sequence.

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In some multibyte encodings, any given multibyte character sequence may represent different characters depending on the previous byte sequences, known as "shift sequences". Such encodings are known as state-dependent: knowledge of the current shift state is required to interpret each character. An NTMBS is only valid if it begins and ends in the initial shift state: if a shift sequence was used, the corresponding unshift sequence has to be present before the terminating null character. Examples of such encodings are BOCU-1 and SCSU.

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A multibyte character string is layout-compatible with null-terminated byte string (NTBS), that is, can be stored, copied, and examined using the same facilities, except for calculating the number of characters. If the correct locale is in effect, I/O functions also handle multibyte strings. Multibyte strings can be converted to and from wide strings using the following locale-dependent conversion functions:

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Multibyte/wide character conversions

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Defined in header <stdlib.h>
returns the number of bytes in the next multibyte character
(function)
converts the next multibyte character to wide character
(function)
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(C11)
 converts a wide character to its multibyte representation
(function)
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(C11)
 converts a narrow multibyte character string to wide string
(function)
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(C11)
 converts a wide string to narrow multibyte character string
(function)
Defined in header <wchar.h>
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(C95)
 checks if the mbstate_t object represents initial shift state
(function)
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(C95)
 widens a single-byte narrow character to wide character, if possible
(function)
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(C95)
 narrows a wide character to a single-byte narrow character, if possible
(function)
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(C95)
 returns the number of bytes in the next multibyte character, given state
(function)
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(C95)
 converts the next multibyte character to wide character, given state
(function)
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(C95)(C11)
 converts a wide character to its multibyte representation, given state
(function)
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(C95)(C11)
 converts a narrow multibyte character string to wide string, given state
(function)
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(C95)(C11)
 converts a wide string to narrow multibyte character string, given state
(function)
Defined in header <uchar.h>
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(C23)
 converts a narrow multibyte character to UTF-8 encoding
(function)
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(C23)
 converts UTF-8 string to narrow multibyte encoding
(function)
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(C11)
 generates the next 16-bit wide character from a narrow multibyte string
(function)
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(C11)
 converts a 16-bit wide character to narrow multibyte string
(function)
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(C11)
 generates the next 32-bit wide character from a narrow multibyte string
(function)
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(C11)
 converts a 32-bit wide character to narrow multibyte string
(function)

Types

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Defined in header <wchar.h>
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(C95)
 conversion state information necessary to iterate multibyte character strings
(class)
Defined in header <uchar.h>
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(C23)
 UTF-8 character type, an alias for unsigned char
(typedef)
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(C11)
 16-bit wide character type
(typedef)
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(C11)
 32-bit wide character type
(typedef)

Macros

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Defined in header <limits.h>
MB_LEN_MAX
 maximum number of bytes in a multibyte character, for any supported locale
(macro constant)
Defined in header <stdlib.h>
MB_CUR_MAX
 maximum number of bytes in a multibyte character, in the current locale
(macro variable)

References

See also

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C++ documentation for Null-terminated multibyte strings
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+ © cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
+ https://en.cppreference.com/w/c/string/multibyte +

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