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UTF8(5)                     BSD File Formats Manual                    UTF8(5)

     utf8 -- UTF-8, a transformation format of ISO 10646


     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 poten-tial potential
     tial security risk, and destroy the 1:1 character:octet sequence mapping.


     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 1_646, January 1998, RFC 2279.

     The Unicode Standard, Version 3._, 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.

     The utf8 encoding is compatible with RFC 2279 and Unicode 3.2.

BSD                              April 7, 2004                             BSD

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