NAME
utf8 —
UTF-8, a transformation format of ISO
10646
SYNOPSIS
ENCODING |
"UTF-8" |
DESCRIPTION
The UTF-8 encoding represents UCS-4
characters as a sequence of octets, using between 1 and 6 for each
character. It is backwards compatible with ASCII, so 0x00-0x7f refer to the
ASCII character set. The multibyte encoding of
non-ASCII characters consist entirely of bytes whose
high order bit is set. The actual encoding is represented by the following
table:
[0x00000000 - 0x0000007f] [00000000.0bbbbbbb] -> 0bbbbbbb [0x00000080 - 0x000007ff] [00000bbb.bbbbbbbb] -> 110bbbbb, 10bbbbbb [0x00000800 - 0x0000ffff] [bbbbbbbb.bbbbbbbb] -> 1110bbbb, 10bbbbbb, 10bbbbbb [0x00010000 - 0x001fffff] [00000000.000bbbbb.bbbbbbbb.bbbbbbbb] -> 11110bbb, 10bbbbbb, 10bbbbbb, 10bbbbbb [0x00200000 - 0x03ffffff] [000000bb.bbbbbbbb.bbbbbbbb.bbbbbbbb] -> 111110bb, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb [0x04000000 - 0x7fffffff] [0bbbbbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb] -> 1111110b, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb
If more than a single representation of a value exists (for example, 0x00; 0xC0 0x80; 0xE0 0x80 0x80) the shortest representation is always used. Longer ones are detected as an error as they pose a potential security risk, and destroy the 1:1 character:octet sequence mapping.
SEE ALSO
Rob Pike and Ken Thompson, Hello World, Proceedings of the Winter 1993 USENIX Technical Conference, USENIX Association, January 1993.
F. Yergeau, UTF-8, a transformation format of ISO 10646, January 1998, RFC 2279.
The Unicode Standard, Version 3.0, The Unicode Consortium, 2000, as amended by the Unicode Standard Annex #27: Unicode 3.1 and by the Unicode Standard Annex #28: Unicode 3.2.
STANDARDS
The utf8 encoding is compatible with RFC
2279 and Unicode 3.2.