89 lines
3.6 KiB
Groff
89 lines
3.6 KiB
Groff
.\" Copyright (c) 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Paul Borman at Krystal Technologies.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)utf2.4 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd June 4, 1993
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.Dt UTF2 4
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.Os
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.Sh NAME
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.Nm utf2
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.Nd "Universal character set Transformation Format encoding of runes
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.Sh SYNOPSIS
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.Nm ENCODING
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.Qq UTF2
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.Sh DESCRIPTION
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The
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.Nm UTF2
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encoding is based on a proposed X-Open multibyte
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\s-1FSS-UCS-TF\s+1 (File System Safe Universal Character Set Transformation Format) encoding as used in
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.Nm Plan 9 from Bell Labs.
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Although it is capable of representing more than 16 bits,
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the current implementation is limited to 16 bits as defined by the
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Unicode Standard.
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.Pp
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.Nm UTF2
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representation is backwards compatible with ASCII, so 0x00-0x7f refer to the
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ASCII character set. The multibyte encoding of runes between 0x0080 and 0xffff
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consist entirely of bytes whose high order bit is set. The actual
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encoding is represented by the following table:
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.Bd -literal
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[0x0000 - 0x007f] [00000000.0bbbbbbb] -> 0bbbbbbb
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[0x0080 - 0x07ff] [00000bbb.bbbbbbbb] -> 110bbbbb, 10bbbbbb
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[0x0800 - 0xffff] [bbbbbbbb.bbbbbbbb] -> 1110bbbb, 10bbbbbb, 10bbbbbb
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.Ed
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.Pp
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If more than a single representation of a value exists (for example,
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0x00; 0xC0 0x80; 0xE0 0x80 0x80) the shortest representation is always
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used (but the longer ones will be correctly decoded).
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.Pp
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The final three encodings provided by X-Open:
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.Bd -literal
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[00000000.000bbbbb.bbbbbbbb.bbbbbbbb] ->
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11110bbb, 10bbbbbb, 10bbbbbb, 10bbbbbb
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[000000bb.bbbbbbbb.bbbbbbbb.bbbbbbbb] ->
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111110bb, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb
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[0bbbbbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb] ->
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1111110b, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb
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.Ed
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.Pp
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which provides for the entire proposed ISO-10646 31 bit standard are currently
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not implemented.
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.Sh "SEE ALSO"
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.Xr mklocale 1 ,
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.Xr setlocale 3
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