135 lines
3.8 KiB
Groff
135 lines
3.8 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. 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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.\" @(#)euc.4 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd September 9, 2019
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.Dt EUC 5
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.Os
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.Sh NAME
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.Nm euc
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.Nd EUC encoding of wide characters
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.Sh SYNOPSIS
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.Nm ENCODING
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.Qq EUC
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.Pp
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.Nm VARIABLE
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.Ar len1
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.Ar mask1
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.Ar len2
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.Ar mask2
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.Ar len3
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.Ar mask3
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.Ar len4
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.Ar mask4
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.Ar mask
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.Sh DESCRIPTION
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.\"The
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.\".Nm EUC
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.\"encoding is provided for compatibility with
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.\".Ux
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.\"based systems.
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.\"See
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.\".Xr localedef 1
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.\"for a complete description of the
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.\".Ev LC_CTYPE
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.\"source file format.
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.\".Pp
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.Nm EUC
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implements a system of 4 multibyte codesets.
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A multibyte character in the first codeset consists of
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.Ar len1
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bytes starting with a byte in the range of 0x00 to 0x7f.
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To allow use of
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.Tn ASCII ,
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.Ar len1
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is always 1.
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A multibyte character in the second codeset consists of
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.Ar len2
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bytes starting with a byte in the range of 0x80-0xff excluding 0x8e and 0x8f.
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A multibyte character in the third codeset consists of
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.Ar len3
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bytes starting with the byte 0x8e.
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A multibyte character in the fourth codeset consists of
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.Ar len4
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bytes starting with the byte 0x8f.
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.Pp
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The
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.Vt wchar_t
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encoding of
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.Nm EUC
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multibyte characters is dependent on the
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.Ar len
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and
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.Ar mask
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arguments.
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First, the bytes are moved into a
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.Vt wchar_t
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as follows:
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.Bd -literal
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byte0 << ((\fIlen\fPN-1) * 8) | byte1 << ((\fIlen\fPN-2) * 8) | ... | byte\fIlen\fPN-1
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.Ed
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.Pp
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The result is then ANDed with
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.Ar ~mask
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and ORed with
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.Ar maskN .
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Codesets 2 and 3 are special in that the leading byte (0x8e or 0x8f) is
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first removed and the
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.Ar lenN
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argument is reduced by 1.
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.Pp
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For example, the
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.Li ja_JP.eucJP
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locale has the following
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.Va VARIABLE
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line:
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.Bd -literal
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VARIABLE 1 0x0000 2 0x8080 2 0x0080 3 0x8000 0x8080
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.Ed
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.Pp
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Codeset 1 consists of the values 0x0000 - 0x007f.
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.Pp
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Codeset 2 consists of the values who have the bits 0x8080 set.
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.Pp
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Codeset 3 consists of the values 0x0080 - 0x00ff.
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.Pp
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Codeset 4 consists of the values 0x8000 - 0xff7f excluding the values
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which have the 0x0080 bit set.
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.Pp
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Notice that the global
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.Ar mask
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is set to 0x8080, this implies that from those 2 bits the codeset can
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be determined.
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.Sh SEE ALSO
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.Xr localedef 1 ,
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.Xr setlocale 3
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