xref: /freebsd/lib/libc/locale/euc.5 (revision dc36d6f9bb1753f3808552f3afd30eda9a7b206a)

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