Difference between revisions of "cpp/string/byte"

Revision as of 14:00, 10 November 2011

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A null-terminated byte string (NTBS) or "narrow string", is a sequence of nonzero bytes followed by a byte with value zero (the terminating null character). Each byte in a narrow string encodes one character of some character set. For example, the character array Template:cpp} is an NTBS holding the string Template:cpp in ASCII encoding.

A null-terminated multibyte string (NTMBS), or "multibyte string", is also a sequence of nonzero bytes followed by a byte with value zero (the terminating null character), but each character stored in the string may occupy more than one byte. For example, the char array Template:cpp} is an NTMBS holding the string Template:cpp in UTF-8 multibyte encoding: the first three bytes encode the character 你, the next three bytes encode the character 好.

An NTMBS is only valid if it begins and ends in the initial shift state: if the string above began with Template:cpp, a byte that cannot appear in the initial shift state of UTF-8 (that is, it cannot be the first byte of a multibyte character), the sequence would not be an NTMBS. A multibyte character string is layout-compatible with narrow character string, that is, can be stored, copied, and examined using the same facilities, except for the length calculation. Multibyte strings can be converted to and from wide strings using appropriate conversion functions.