mirror of
https://git.savannah.gnu.org/git/emacs.git
synced 2024-11-22 07:09:54 +00:00
Comment changes.
This commit is contained in:
Richard M. Stallman
parent
c49f3d5a65
commit
f4dee5826e
116
src/coding.c
116
src/coding.c
@ -44,41 +44,40 @@ Boston, MA 02111-1307, USA. */
|
||||
0. Emacs' internal format (emacs-mule)
|
||||
|
||||
Emacs itself holds a multi-lingual character in a buffer and a string
|
||||
in a special format. Details are described in the section 2.
|
||||
in a special format. Details are described in section 2.
|
||||
|
||||
1. ISO2022
|
||||
|
||||
The most famous coding system for multiple character sets. X's
|
||||
Compound Text, various EUCs (Extended Unix Code), and such coding
|
||||
systems used in Internet communication as ISO-2022-JP are all
|
||||
variants of ISO2022. Details are described in the section 3.
|
||||
Compound Text, various EUCs (Extended Unix Code), and coding
|
||||
systems used in Internet communication such as ISO-2022-JP are
|
||||
all variants of ISO2022. Details are described in section 3.
|
||||
|
||||
2. SJIS (or Shift-JIS or MS-Kanji-Code)
|
||||
|
||||
A coding system to encode character sets: ASCII, JISX0201, and
|
||||
JISX0208. Widely used for PC's in Japan. Details are described in
|
||||
the section 4.
|
||||
section 4.
|
||||
|
||||
3. BIG5
|
||||
|
||||
A coding system to encode character sets: ASCII and Big5. Widely
|
||||
used by Chinese (mainly in Taiwan and Hong Kong). Details are
|
||||
described in the section 4. In this file, when written as "BIG5"
|
||||
(all uppercase), it means the coding system, and when written as
|
||||
"Big5" (capitalized), it means the character set.
|
||||
described in section 4. In this file, when we write "BIG5"
|
||||
(all uppercase), we mean the coding system, and when we write
|
||||
"Big5" (capitalized), we mean the character set.
|
||||
|
||||
4. Else
|
||||
4. Other
|
||||
|
||||
If a user want to read/write a text encoded in a coding system not
|
||||
If a user wants to read/write a text encoded in a coding system not
|
||||
listed above, he can supply a decoder and an encoder for it in CCL
|
||||
(Code Conversion Language) programs. Emacs executes the CCL program
|
||||
while reading/writing.
|
||||
|
||||
Emacs represent a coding-system by a Lisp symbol that has a property
|
||||
Emacs represents a coding-system by a Lisp symbol that has a property
|
||||
`coding-system'. But, before actually using the coding-system, the
|
||||
information about it is set in a structure of type `struct
|
||||
coding_system' for rapid processing. See the section 6 for more
|
||||
detail.
|
||||
coding_system' for rapid processing. See section 6 for more details.
|
||||
|
||||
*/
|
||||
|
||||
@ -86,14 +85,13 @@ Boston, MA 02111-1307, USA. */
|
||||
|
||||
How end-of-line of a text is encoded depends on a system. For
|
||||
instance, Unix's format is just one byte of `line-feed' code,
|
||||
whereas DOS's format is two bytes sequence of `carriage-return' and
|
||||
whereas DOS's format is two-byte sequence of `carriage-return' and
|
||||
`line-feed' codes. MacOS's format is one byte of `carriage-return'.
|
||||
|
||||
Since how characters in a text is encoded and how end-of-line is
|
||||
encoded is independent, any coding system described above can take
|
||||
Since text characters encoding and end-of-line encoding are
|
||||
independent, any coding system described above can take
|
||||
any format of end-of-line. So, Emacs has information of format of
|
||||
end-of-line in each coding-system. See the section 6 for more
|
||||
detail.
|
||||
end-of-line in each coding-system. See section 6 for more details.
|
||||
|
||||
*/
|
||||
|
||||
@ -117,10 +115,10 @@ detect_coding_emacs_mule (src, src_end)
|
||||
|
||||
These functions decode SRC_BYTES length text at SOURCE encoded in
|
||||
CODING to Emacs' internal format (emacs-mule). The resulting text
|
||||
goes to a place pointed by DESTINATION, the length of which should
|
||||
not exceed DST_BYTES. The bytes actually processed is returned as
|
||||
*CONSUMED. The return value is the length of the decoded text.
|
||||
Below is a template of these functions. */
|
||||
goes to a place pointed to by DESTINATION, the length of which should
|
||||
not exceed DST_BYTES. The number of bytes actually processed is
|
||||
returned as *CONSUMED. The return value is the length of the decoded
|
||||
text. Below is a template of these functions. */
|
||||
#if 0
|
||||
decode_coding_XXX (coding, source, destination, src_bytes, dst_bytes, consumed)
|
||||
struct coding_system *coding;
|
||||
@ -136,10 +134,10 @@ decode_coding_XXX (coding, source, destination, src_bytes, dst_bytes, consumed)
|
||||
|
||||
These functions encode SRC_BYTES length text at SOURCE of Emacs'
|
||||
internal format (emacs-mule) to CODING. The resulting text goes to
|
||||
a place pointed by DESTINATION, the length of which should not
|
||||
exceed DST_BYTES. The bytes actually processed is returned as
|
||||
*CONSUMED. The return value is the length of the encoded text.
|
||||
Below is a template of these functions. */
|
||||
a place pointed to by DESTINATION, the length of which should not
|
||||
exceed DST_BYTES. The number of bytes actually processed is
|
||||
returned as *CONSUMED. The return value is the length of the
|
||||
encoded text. Below is a template of these functions. */
|
||||
#if 0
|
||||
encode_coding_XXX (coding, source, destination, src_bytes, dst_bytes, consumed)
|
||||
struct coding_system *coding;
|
||||
@ -200,7 +198,7 @@ encode_coding_XXX (coding, source, destination, src_bytes, dst_bytes, consumed)
|
||||
*dst++ = (c); \
|
||||
} while (0)
|
||||
|
||||
/* Decode one DIMENSION1 character of which charset is CHARSET and
|
||||
/* Decode one DIMENSION1 character whose charset is CHARSET and whose
|
||||
position-code is C. */
|
||||
|
||||
#define DECODE_CHARACTER_DIMENSION1(charset, c) \
|
||||
@ -215,7 +213,7 @@ encode_coding_XXX (coding, source, destination, src_bytes, dst_bytes, consumed)
|
||||
*dst++ = (c) | 0x80; \
|
||||
} while (0)
|
||||
|
||||
/* Decode one DIMENSION2 character of which charset is CHARSET and
|
||||
/* Decode one DIMENSION2 character whose charset is CHARSET and whose
|
||||
position-codes are C1 and C2. */
|
||||
|
||||
#define DECODE_CHARACTER_DIMENSION2(charset, c1, c2) \
|
||||
@ -337,25 +335,25 @@ Lisp_Object Vdefault_process_coding_system;
|
||||
/*** 2. Emacs internal format (emacs-mule) handlers ***/
|
||||
|
||||
/* Emacs' internal format for encoding multiple character sets is a
|
||||
kind of multi-byte encoding, i.e. encoding a character by a sequence
|
||||
of one-byte codes of variable length. ASCII characters and control
|
||||
characters (e.g. `tab', `newline') are represented by one-byte as
|
||||
is. It takes the range 0x00 through 0x7F. The other characters
|
||||
are represented by a sequence of `base leading-code', optional
|
||||
`extended leading-code', and one or two `position-code's. Length
|
||||
of the sequence is decided by the base leading-code. Leading-code
|
||||
takes the range 0x80 through 0x9F, whereas extended leading-code
|
||||
and position-code take the range 0xA0 through 0xFF. See the
|
||||
document of `charset.h' for more detail about leading-code and
|
||||
position-code.
|
||||
kind of multi-byte encoding, i.e. characters are encoded by
|
||||
variable-length sequences of one-byte codes. ASCII characters
|
||||
and control characters (e.g. `tab', `newline') are represented by
|
||||
one-byte sequences which are their ASCII codes, in the range 0x00
|
||||
through 0x7F. The other characters are represented by a sequence
|
||||
of `base leading-code', optional `extended leading-code', and one
|
||||
or two `position-code's. The length of the sequence is determined
|
||||
by the base leading-code. Leading-code takes the range 0x80
|
||||
through 0x9F, whereas extended leading-code and position-code take
|
||||
the range 0xA0 through 0xFF. See `charset.h' for more details
|
||||
about leading-code and position-code.
|
||||
|
||||
There's one exception in this rule. Special leading-code
|
||||
There's one exception to this rule. Special leading-code
|
||||
`leading-code-composition' denotes that the following several
|
||||
characters should be composed into one character. Leading-codes of
|
||||
components (except for ASCII) are added 0x20. An ASCII character
|
||||
component is represented by a 2-byte sequence of `0xA0' and
|
||||
`ASCII-code + 0x80'. See also the document in `charset.h' for the
|
||||
detail of composite character. Hence, we can summarize the code
|
||||
`ASCII-code + 0x80'. See also the comments in `charset.h' for the
|
||||
details of composite character. Hence, we can summarize the code
|
||||
range as follows:
|
||||
|
||||
--- CODE RANGE of Emacs' internal format ---
|
||||
@ -447,21 +445,21 @@ detect_coding_emacs_mule (src, src_end)
|
||||
/*** 3. ISO2022 handlers ***/
|
||||
|
||||
/* The following note describes the coding system ISO2022 briefly.
|
||||
Since the intension of this note is to help understanding of the
|
||||
programs in this file, some parts are NOT ACCURATE or OVERLY
|
||||
Since the intention of this note is to help in understanding of
|
||||
the programs in this file, some parts are NOT ACCURATE or OVERLY
|
||||
SIMPLIFIED. For the thorough understanding, please refer to the
|
||||
original document of ISO2022.
|
||||
|
||||
ISO2022 provides many mechanisms to encode several character sets
|
||||
in 7-bit and 8-bit environment. If one choose 7-bite environment,
|
||||
in 7-bit and 8-bit environment. If one chooses 7-bite environment,
|
||||
all text is encoded by codes of less than 128. This may make the
|
||||
encoded text a little bit longer, but the text get more stability
|
||||
to pass through several gateways (some of them split MSB off).
|
||||
encoded text a little bit longer, but the text gets more stability
|
||||
to pass through several gateways (some of them strip off the MSB).
|
||||
|
||||
There are two kind of character set: control character set and
|
||||
There are two kinds of character set: control character set and
|
||||
graphic character set. The former contains control characters such
|
||||
as `newline' and `escape' to provide control functions (control
|
||||
functions are provided also by escape sequence). The latter
|
||||
functions are provided also by escape sequences). The latter
|
||||
contains graphic characters such as ' A' and '-'. Emacs recognizes
|
||||
two control character sets and many graphic character sets.
|
||||
|
||||
@ -565,7 +563,7 @@ detect_coding_emacs_mule (src, src_end)
|
||||
'(' can be omitted. We call this as "short-form" here after.
|
||||
|
||||
Now you may notice that there are a lot of ways for encoding the
|
||||
same multilingual text in ISO2022. Actually, there exist many
|
||||
same multilingual text in ISO2022. Actually, there exists many
|
||||
coding systems such as Compound Text (used in X's inter client
|
||||
communication, ISO-2022-JP (used in Japanese Internet), ISO-2022-KR
|
||||
(used in Korean Internet), EUC (Extended UNIX Code, used in Asian
|
||||
@ -1018,10 +1016,10 @@ decode_coding_iso2022 (coding, source, destination,
|
||||
return dst - destination;
|
||||
}
|
||||
|
||||
/* ISO2022 encoding staffs. */
|
||||
/* ISO2022 encoding stuff. */
|
||||
|
||||
/*
|
||||
It is not enough to say just "ISO2022" on encoding, but we have to
|
||||
It is not enough to say just "ISO2022" on encoding, we have to
|
||||
specify more details. In Emacs, each coding-system of ISO2022
|
||||
variant has the following specifications:
|
||||
1. Initial designation to G0 thru G3.
|
||||
@ -1036,7 +1034,7 @@ decode_coding_iso2022 (coding, source, destination,
|
||||
9. Use JISX0208-1983 in place of JISX0208-1978?
|
||||
These specifications are encoded in `coding->flags' as flag bits
|
||||
defined by macros CODING_FLAG_ISO_XXX. See `coding.h' for more
|
||||
detail.
|
||||
details.
|
||||
*/
|
||||
|
||||
/* Produce codes (escape sequence) for designating CHARSET to graphic
|
||||
@ -1132,8 +1130,8 @@ decode_coding_iso2022 (coding, source, destination,
|
||||
CODING_SPEC_ISO_INVOCATION (coding, 0) = 3; \
|
||||
} while (0)
|
||||
|
||||
/* Produce codes for a DIMENSION1 character of which character set is
|
||||
CHARSET and position-code is C1. Designation and invocation
|
||||
/* Produce codes for a DIMENSION1 character whose character set is
|
||||
CHARSET and whose position-code is C1. Designation and invocation
|
||||
sequences are also produced in advance if necessary. */
|
||||
|
||||
|
||||
@ -1166,8 +1164,8 @@ decode_coding_iso2022 (coding, source, destination,
|
||||
dst = encode_invocation_designation (charset, coding, dst); \
|
||||
} while (1)
|
||||
|
||||
/* Produce codes for a DIMENSION2 character of which character set is
|
||||
CHARSET and position-codes are C1 and C2. Designation and
|
||||
/* Produce codes for a DIMENSION2 character whose character set is
|
||||
CHARSET and whose position-codes are C1 and C2. Designation and
|
||||
invocation codes are also produced in advance if necessary. */
|
||||
|
||||
#define ENCODE_ISO_CHARACTER_DIMENSION2(charset, c1, c2) \
|
||||
@ -1552,7 +1550,7 @@ encode_coding_iso2022 (coding, source, destination,
|
||||
|
||||
/*** 4. SJIS and BIG5 handlers ***/
|
||||
|
||||
/* Although SJIS and BIG5 are not ISO's coding system, They are used
|
||||
/* Although SJIS and BIG5 are not ISO's coding system, they are used
|
||||
quite widely. So, for the moment, Emacs supports them in the bare
|
||||
C code. But, in the future, they may be supported only by CCL. */
|
||||
|
||||
@ -2167,7 +2165,7 @@ setup_coding_system (coding_system, coding)
|
||||
{
|
||||
Lisp_Object type, eol_type;
|
||||
|
||||
/* At first, set several fields default values. */
|
||||
/* At first, set several fields to default values. */
|
||||
coding->require_flushing = 0;
|
||||
coding->last_block = 0;
|
||||
coding->selective = 0;
|
||||
|
||||
Loading…
Reference in New Issue
Block a user