[mule-ja-2009:09610] Re: Emacs22 =?ISO-2022-JP?B?GyRCJEgbKEI=?= Emacs23 =?ISO-2022-JP?B?GyRCJEcbKEI=?= char-after =?ISO-2022-JP?B?GyRCJE43azJMJCwwYyQmGyhC?=

[Kenichi Handa <handa@xxxxxxxx>]

In article <20090711.144725.243103832.masutaka@xxxxxxxxx>, Takashi Masuda (=?iso-2022-jp?B?GyRCQX1FRDUuO04bKEI=?=) <masutaka@xxxxxxxxx> writes:

> ちょっと調べてみたところ、Emacs22 までは
>  0xC000 + JIS上位バイト*128 + JIS下位バイト
> といった独自のコードで持っているようですね。

> # "次" という文字の JIS コードは 0x3C21 なので
> #  0xC000 + (0x3C * 0x80) + 0x21 = 0xDE21 -> 56865

Emacs 22 の文字コードは正確には以下のようになっていました
(excerpt from src/charset.h)。

  Emacs uses 19 bits for a character code.  The bits are divided into
  3 fields: FIELD1(5bits):FIELD2(7bits):FIELD3(7bits).

  A character code of DIMENSION1 character uses FIELD2 to hold charset
  and FIELD3 to hold POSITION-CODE-1.  A character code of DIMENSION2
  character uses FIELD1 to hold charset, FIELD2 and FIELD3 to hold
  POSITION-CODE-1 and POSITION-CODE-2 respectively.

  More precisely...

  FIELD2 of DIMENSION1 character (except for ascii, eight-bit-control,
  and eight-bit-graphic) is "charset - 0x70".  This is to make all
  character codes except for ASCII and 8-bit codes greater than 256.
  So, the range of FIELD2 of DIMENSION1 character is 0, 1, or
  0x11..0x7F.

  FIELD1 of DIMENSION2 character is "charset - 0x8F" for official
  charset and "charset - 0xE0" for private charset.  So, the range of
  FIELD1 of DIMENSION2 character is 0x01..0x1E.

  -----------------------------------------------------------------------------
  charset		FIELD1 (5-bit)	    FIELD2 (7-bit)	FIELD3 (7-bit)
  -----------------------------------------------------------------------------
  ascii			0		    0			0x00..0x7F
  eight-bit-control	0		    1			0x00..0x1F
  eight-bit-graphic	0		    1			0x20..0x7F
  DIMENSION1		0		    charset - 0x70	POSITION-CODE-1
  DIMENSION2(o)		charset - 0x8F	    POSITION-CODE-1	POSITION-CODE-2
  DIMENSION2(p)		charset - 0xE0	    POSITION-CODE-1	POSITION-CODE-2
  -----------------------------------------------------------------------------
  "(o)": official, "(p)": private
  -----------------------------------------------------------------------------

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半田＠ＡＩＳＴ