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-File: lispref.info, Node: Coding System Properties, Next: Basic Coding System Functions, Prev: EOL Conversion, Up: Coding Systems
-
-Coding System Properties
-------------------------
-
-`mnemonic'
- String to be displayed in the modeline when this coding system is
- active.
-
-`eol-type'
- End-of-line conversion to be used. It should be one of the types
- listed in *Note EOL Conversion::.
-
-`eol-lf'
- The coding system which is the same as this one, except that it
- uses the Unix line-breaking convention.
-
-`eol-crlf'
- The coding system which is the same as this one, except that it
- uses the DOS line-breaking convention.
-
-`eol-cr'
- The coding system which is the same as this one, except that it
- uses the Macintosh line-breaking convention.
-
-`post-read-conversion'
- Function called after a file has been read in, to perform the
- decoding. Called with two arguments, BEG and END, denoting a
- region of the current buffer to be decoded.
-
-`pre-write-conversion'
- Function called before a file is written out, to perform the
- encoding. Called with two arguments, BEG and END, denoting a
- region of the current buffer to be encoded.
-
- The following additional properties are recognized if TYPE is
-`iso2022':
-
-`charset-g0'
-`charset-g1'
-`charset-g2'
-`charset-g3'
- The character set initially designated to the G0 - G3 registers.
- The value should be one of
-
- * A charset object (designate that character set)
-
- * `nil' (do not ever use this register)
-
- * `t' (no character set is initially designated to the
- register, but may be later on; this automatically sets the
- corresponding `force-g*-on-output' property)
-
-`force-g0-on-output'
-`force-g1-on-output'
-`force-g2-on-output'
-`force-g3-on-output'
- If non-`nil', send an explicit designation sequence on output
- before using the specified register.
-
-`short'
- If non-`nil', use the short forms `ESC $ @', `ESC $ A', and `ESC $
- B' on output in place of the full designation sequences `ESC $ (
- @', `ESC $ ( A', and `ESC $ ( B'.
-
-`no-ascii-eol'
- If non-`nil', don't designate ASCII to G0 at each end of line on
- output. Setting this to non-`nil' also suppresses other
- state-resetting that normally happens at the end of a line.
-
-`no-ascii-cntl'
- If non-`nil', don't designate ASCII to G0 before control chars on
- output.
-
-`seven'
- If non-`nil', use 7-bit environment on output. Otherwise, use
- 8-bit environment.
-
-`lock-shift'
- If non-`nil', use locking-shift (SO/SI) instead of single-shift or
- designation by escape sequence.
-
-`no-iso6429'
- If non-`nil', don't use ISO6429's direction specification.
-
-`escape-quoted'
- If non-nil, literal control characters that are the same as the
- beginning of a recognized ISO 2022 or ISO 6429 escape sequence (in
- particular, ESC (0x1B), SO (0x0E), SI (0x0F), SS2 (0x8E), SS3
- (0x8F), and CSI (0x9B)) are "quoted" with an escape character so
- that they can be properly distinguished from an escape sequence.
- (Note that doing this results in a non-portable encoding.) This
- encoding flag is used for byte-compiled files. Note that ESC is a
- good choice for a quoting character because there are no escape
- sequences whose second byte is a character from the Control-0 or
- Control-1 character sets; this is explicitly disallowed by the ISO
- 2022 standard.
-
-`input-charset-conversion'
- A list of conversion specifications, specifying conversion of
- characters in one charset to another when decoding is performed.
- Each specification is a list of two elements: the source charset,
- and the destination charset.
-
-`output-charset-conversion'
- A list of conversion specifications, specifying conversion of
- characters in one charset to another when encoding is performed.
- The form of each specification is the same as for
- `input-charset-conversion'.
-
- The following additional properties are recognized (and required) if
-TYPE is `ccl':
-
-`decode'
- CCL program used for decoding (converting to internal format).
-
-`encode'
- CCL program used for encoding (converting to external format).
-
- The following properties are used internally: EOL-CR, EOL-CRLF,
-EOL-LF, and BASE.
-
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-File: lispref.info, Node: Basic Coding System Functions, Next: Coding System Property Functions, Prev: Coding System Properties, Up: Coding Systems
-
-Basic Coding System Functions
------------------------------
-
- - Function: find-coding-system coding-system-or-name
- This function retrieves the coding system of the given name.
-
- If CODING-SYSTEM-OR-NAME is a coding-system object, it is simply
- returned. Otherwise, CODING-SYSTEM-OR-NAME should be a symbol.
- If there is no such coding system, `nil' is returned. Otherwise
- the associated coding system object is returned.
-
- - Function: get-coding-system name
- This function retrieves the coding system of the given name. Same
- as `find-coding-system' except an error is signalled if there is no
- such coding system instead of returning `nil'.
-
- - Function: coding-system-list
- This function returns a list of the names of all defined coding
- systems.
-
- - Function: coding-system-name coding-system
- This function returns the name of the given coding system.
-
- - Function: coding-system-base coding-system
- Returns the base coding system (undecided EOL convention) coding
- system.
-
- - Function: make-coding-system name type &optional doc-string props
- This function registers symbol NAME as a coding system.
-
- TYPE describes the conversion method used and should be one of the
- types listed in *Note Coding System Types::.
-
- DOC-STRING is a string describing the coding system.
-
- PROPS is a property list, describing the specific nature of the
- character set. Recognized properties are as in *Note Coding
- System Properties::.
-
- - Function: copy-coding-system old-coding-system new-name
- This function copies OLD-CODING-SYSTEM to NEW-NAME. If NEW-NAME
- does not name an existing coding system, a new one will be created.
-
- - Function: subsidiary-coding-system coding-system eol-type
- This function returns the subsidiary coding system of
- CODING-SYSTEM with eol type EOL-TYPE.
-
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-File: lispref.info, Node: Coding System Property Functions, Next: Encoding and Decoding Text, Prev: Basic Coding System Functions, Up: Coding Systems
-
-Coding System Property Functions
---------------------------------
-
- - Function: coding-system-doc-string coding-system
- This function returns the doc string for CODING-SYSTEM.
-
- - Function: coding-system-type coding-system
- This function returns the type of CODING-SYSTEM.
-
- - Function: coding-system-property coding-system prop
- This function returns the PROP property of CODING-SYSTEM.
-
-\1f
-File: lispref.info, Node: Encoding and Decoding Text, Next: Detection of Textual Encoding, Prev: Coding System Property Functions, Up: Coding Systems
-
-Encoding and Decoding Text
---------------------------
-
- - Function: decode-coding-region start end coding-system &optional
- buffer
- This function decodes the text between START and END which is
- encoded in CODING-SYSTEM. This is useful if you've read in
- encoded text from a file without decoding it (e.g. you read in a
- JIS-formatted file but used the `binary' or `no-conversion' coding
- system, so that it shows up as `^[$B!<!+^[(B'). The length of the
- encoded text is returned. BUFFER defaults to the current buffer
- if unspecified.
-
- - Function: encode-coding-region start end coding-system &optional
- buffer
- This function encodes the text between START and END using
- CODING-SYSTEM. This will, for example, convert Japanese
- characters into stuff such as `^[$B!<!+^[(B' if you use the JIS
- encoding. The length of the encoded text is returned. BUFFER
- defaults to the current buffer if unspecified.
-
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-File: lispref.info, Node: Detection of Textual Encoding, Next: Big5 and Shift-JIS Functions, Prev: Encoding and Decoding Text, Up: Coding Systems
-
-Detection of Textual Encoding
------------------------------
-
- - Function: coding-category-list
- This function returns a list of all recognized coding categories.
-
- - Function: set-coding-priority-list list
- This function changes the priority order of the coding categories.
- LIST should be a list of coding categories, in descending order of
- priority. Unspecified coding categories will be lower in priority
- than all specified ones, in the same relative order they were in
- previously.
-
- - Function: coding-priority-list
- This function returns a list of coding categories in descending
- order of priority.
-
- - Function: set-coding-category-system coding-category coding-system
- This function changes the coding system associated with a coding
- category.
-
- - Function: coding-category-system coding-category
- This function returns the coding system associated with a coding
- category.
-
- - Function: detect-coding-region start end &optional buffer
- This function detects coding system of the text in the region
- between START and END. Returned value is a list of possible coding
- systems ordered by priority. If only ASCII characters are found,
- it returns `autodetect' or one of its subsidiary coding systems
- according to a detected end-of-line type. Optional arg BUFFER
- defaults to the current buffer.
-
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-File: lispref.info, Node: Big5 and Shift-JIS Functions, Next: Predefined Coding Systems, Prev: Detection of Textual Encoding, Up: Coding Systems
-
-Big5 and Shift-JIS Functions
-----------------------------
-
- These are special functions for working with the non-standard
-Shift-JIS and Big5 encodings.
-
- - Function: decode-shift-jis-char code
- This function decodes a JIS X 0208 character of Shift-JIS
- coding-system. CODE is the character code in Shift-JIS as a cons
- of type bytes. The corresponding character is returned.
-
- - Function: encode-shift-jis-char ch
- This function encodes a JIS X 0208 character CH to SHIFT-JIS
- coding-system. The corresponding character code in SHIFT-JIS is
- returned as a cons of two bytes.
-
- - Function: decode-big5-char code
- This function decodes a Big5 character CODE of BIG5 coding-system.
- CODE is the character code in BIG5. The corresponding character
- is returned.
-
- - Function: encode-big5-char ch
- This function encodes the Big5 character CHAR to BIG5
- coding-system. The corresponding character code in Big5 is
- returned.
-
-\1f
-File: lispref.info, Node: Predefined Coding Systems, Prev: Big5 and Shift-JIS Functions, Up: Coding Systems
-
-Coding Systems Implemented
---------------------------
-
- MULE initializes most of the commonly used coding systems at XEmacs's
-startup. A few others are initialized only when the relevant language
-environment is selected and support libraries are loaded. (NB: The
-following list is based on XEmacs 21.2.19, the development branch at the
-time of writing. The list may be somewhat different for other
-versions. Recent versions of GNU Emacs 20 implement a few more rare
-coding systems; work is being done to port these to XEmacs.)
-
- Unfortunately, there is not a consistent naming convention for
-character sets, and for practical purposes coding systems often take
-their name from their principal character sets (ASCII, KOI8-R, Shift
-JIS). Others take their names from the coding system (ISO-2022-JP,
-EUC-KR), and a few from their non-text usages (internal, binary). To
-provide for this, and for the fact that many coding systems have
-several common names, an aliasing system is provided. Finally, some
-effort has been made to use names that are registered as MIME charsets
-(this is why the name 'shift_jis contains that un-Lisp-y underscore).
-
- There is a systematic naming convention regarding end-of-line (EOL)
-conventions for different systems. A coding system whose name ends in
-"-unix" forces the assumptions that lines are broken by newlines (0x0A).
-A coding system whose name ends in "-mac" forces the assumptions that
-lines are broken by ASCII CRs (0x0D). A coding system whose name ends
-in "-dos" forces the assumptions that lines are broken by CRLF sequences
-(0x0D 0x0A). These subsidiary coding systems are automatically derived
-from a base coding system. Use of the base coding system implies
-autodetection of the text file convention. (The fact that the -unix,
--mac, and -dos are derived from a base system results in them showing up
-as "aliases" in `list-coding-systems'.) These subsidiaries have a
-consistent modeline indicator as well. "-dos" coding systems have ":T"
-appended to their modeline indicator, while "-mac" coding systems have
-":t" appended (eg, "ISO8:t" for iso-2022-8-mac).
-
- In the following table, each coding system is given with its mode
-line indicator in parentheses. Non-textual coding systems are listed
-first, followed by textual coding systems and their aliases. (The
-coding system subsidiary modeline indicators ":T" and ":t" will be
-omitted from the table of coding systems.)
-
- ### SJT 1999-08-23 Maybe should order these by language? Definitely
-need language usage for the ISO-8859 family.
-
- Note that although true coding system aliases have been implemented
-for XEmacs 21.2, the coding system initialization has not yet been
-converted as of 21.2.19. So coding systems described as aliases have
-the same properties as the aliased coding system, but will not be equal
-as Lisp objects.
-
-`automatic-conversion'
-`undecided'
-`undecided-dos'
-`undecided-mac'
-`undecided-unix'
- Modeline indicator: `Auto'. A type `undecided' coding system.
- Attempts to determine an appropriate coding system from file
- contents or the environment.
-
-`raw-text'
-`no-conversion'
-`raw-text-dos'
-`raw-text-mac'
-`raw-text-unix'
-`no-conversion-dos'
-`no-conversion-mac'
-`no-conversion-unix'
- Modeline indicator: `Raw'. A type `no-conversion' coding system,
- which converts only line-break-codes. An implementation quirk
- means that this coding system is also used for ISO8859-1.
-
-`binary'
- Modeline indicator: `Binary'. A type `no-conversion' coding
- system which does no character coding or EOL conversions. An
- alias for `raw-text-unix'.
-
-`alternativnyj'
-`alternativnyj-dos'
-`alternativnyj-mac'
-`alternativnyj-unix'
- Modeline indicator: `Cy.Alt'. A type `ccl' coding system used for
- Alternativnyj, an encoding of the Cyrillic alphabet.
-
-`big5'
-`big5-dos'
-`big5-mac'
-`big5-unix'
- Modeline indicator: `Zh/Big5'. A type `big5' coding system used
- for BIG5, the most common encoding of traditional Chinese as used
- in Taiwan.
-
-`cn-gb-2312'
-`cn-gb-2312-dos'
-`cn-gb-2312-mac'
-`cn-gb-2312-unix'
- Modeline indicator: `Zh-GB/EUC'. A type `iso2022' coding system
- used for simplified Chinese (as used in the People's Republic of
- China), with the `ascii' (G0), `chinese-gb2312' (G1), and `sisheng'
- (G2) character sets initially designated. Chinese EUC (Extended
- Unix Code).
-
-`ctext-hebrew'
-`ctext-hebrew-dos'
-`ctext-hebrew-mac'
-`ctext-hebrew-unix'
- Modeline indicator: `CText/Hbrw'. A type `iso2022' coding system
- with the `ascii' (G0) and `hebrew-iso8859-8' (G1) character sets
- initially designated for Hebrew.
-
-`ctext'
-`ctext-dos'
-`ctext-mac'
-`ctext-unix'
- Modeline indicator: `CText'. A type `iso2022' 8-bit coding system
- with the `ascii' (G0) and `latin-iso8859-1' (G1) character sets
- initially designated. X11 Compound Text Encoding. Often
- mistakenly recognized instead of EUC encodings; usual cause is
- inappropriate setting of `coding-priority-list'.
-
-`escape-quoted'
- Modeline indicator: `ESC/Quot'. A type `iso2022' 8-bit coding
- system with the `ascii' (G0) and `latin-iso8859-1' (G1) character
- sets initially designated and escape quoting. Unix EOL conversion
- (ie, no conversion). It is used for .ELC files.
-
-`euc-jp'
-`euc-jp-dos'
-`euc-jp-mac'
-`euc-jp-unix'
- Modeline indicator: `Ja/EUC'. A type `iso2022' 8-bit coding system
- with `ascii' (G0), `japanese-jisx0208' (G1), `katakana-jisx0201'
- (G2), and `japanese-jisx0212' (G3) initially designated. Japanese
- EUC (Extended Unix Code).
-
-`euc-kr'
-`euc-kr-dos'
-`euc-kr-mac'
-`euc-kr-unix'
- Modeline indicator: `ko/EUC'. A type `iso2022' 8-bit coding system
- with `ascii' (G0) and `korean-ksc5601' (G1) initially designated.
- Korean EUC (Extended Unix Code).
-
-`hz-gb-2312'
- Modeline indicator: `Zh-GB/Hz'. A type `no-conversion' coding
- system with Unix EOL convention (ie, no conversion) using
- post-read-decode and pre-write-encode functions to translate the
- Hz/ZW coding system used for Chinese.
-
-`iso-2022-7bit'
-`iso-2022-7bit-unix'
-`iso-2022-7bit-dos'
-`iso-2022-7bit-mac'
-`iso-2022-7'
- Modeline indicator: `ISO7'. A type `iso2022' 7-bit coding system
- with `ascii' (G0) initially designated. Other character sets must
- be explicitly designated to be used.
-
-`iso-2022-7bit-ss2'
-`iso-2022-7bit-ss2-dos'
-`iso-2022-7bit-ss2-mac'
-`iso-2022-7bit-ss2-unix'
- Modeline indicator: `ISO7/SS'. A type `iso2022' 7-bit coding
- system with `ascii' (G0) initially designated. Other character
- sets must be explicitly designated to be used. SS2 is used to
- invoke a 96-charset, one character at a time.
-
-`iso-2022-8'
-`iso-2022-8-dos'
-`iso-2022-8-mac'
-`iso-2022-8-unix'
- Modeline indicator: `ISO8'. A type `iso2022' 8-bit coding system
- with `ascii' (G0) and `latin-iso8859-1' (G1) initially designated.
- Other character sets must be explicitly designated to be used.
- No single-shift or locking-shift.
-
-`iso-2022-8bit-ss2'
-`iso-2022-8bit-ss2-dos'
-`iso-2022-8bit-ss2-mac'
-`iso-2022-8bit-ss2-unix'
- Modeline indicator: `ISO8/SS'. A type `iso2022' 8-bit coding
- system with `ascii' (G0) and `latin-iso8859-1' (G1) initially
- designated. Other character sets must be explicitly designated to
- be used. SS2 is used to invoke a 96-charset, one character at a
- time.
-
-`iso-2022-int-1'
-`iso-2022-int-1-dos'
-`iso-2022-int-1-mac'
-`iso-2022-int-1-unix'
- Modeline indicator: `INT-1'. A type `iso2022' 7-bit coding system
- with `ascii' (G0) and `korean-ksc5601' (G1) initially designated.
- ISO-2022-INT-1.
-
-`iso-2022-jp-1978-irv'
-`iso-2022-jp-1978-irv-dos'
-`iso-2022-jp-1978-irv-mac'
-`iso-2022-jp-1978-irv-unix'
- Modeline indicator: `Ja-78/7bit'. A type `iso2022' 7-bit coding
- system. For compatibility with old Japanese terminals; if you
- need to know, look at the source.
-
-`iso-2022-jp'
-`iso-2022-jp-2 (ISO7/SS)'
-`iso-2022-jp-dos'
-`iso-2022-jp-mac'
-`iso-2022-jp-unix'
-`iso-2022-jp-2-dos'
-`iso-2022-jp-2-mac'
-`iso-2022-jp-2-unix'
- Modeline indicator: `MULE/7bit'. A type `iso2022' 7-bit coding
- system with `ascii' (G0) initially designated, and complex
- specifications to insure backward compatibility with old Japanese
- systems. Used for communication with mail and news in Japan. The
- "-2" versions also use SS2 to invoke a 96-charset one character at
- a time.
-
-`iso-2022-kr'
- Modeline indicator: `Ko/7bit' A type `iso2022' 7-bit coding
- system with `ascii' (G0) and `korean-ksc5601' (G1) initially
- designated. Used for e-mail in Korea.
-
-`iso-2022-lock'
-`iso-2022-lock-dos'
-`iso-2022-lock-mac'
-`iso-2022-lock-unix'
- Modeline indicator: `ISO7/Lock'. A type `iso2022' 7-bit coding
- system with `ascii' (G0) initially designated, using Locking-Shift
- to invoke a 96-charset.
-
-`iso-8859-1'
-`iso-8859-1-dos'
-`iso-8859-1-mac'
-`iso-8859-1-unix'
- Due to implementation, this is not a type `iso2022' coding system,
- but rather an alias for the `raw-text' coding system.
-
-`iso-8859-2'
-`iso-8859-2-dos'
-`iso-8859-2-mac'
-`iso-8859-2-unix'
- Modeline indicator: `MIME/Ltn-2'. A type `iso2022' coding system
- with `ascii' (G0) and `latin-iso8859-2' (G1) initially invoked.
-
-`iso-8859-3'
-`iso-8859-3-dos'
-`iso-8859-3-mac'
-`iso-8859-3-unix'
- Modeline indicator: `MIME/Ltn-3'. A type `iso2022' coding system
- with `ascii' (G0) and `latin-iso8859-3' (G1) initially invoked.
-
-`iso-8859-4'
-`iso-8859-4-dos'
-`iso-8859-4-mac'
-`iso-8859-4-unix'
- Modeline indicator: `MIME/Ltn-4'. A type `iso2022' coding system
- with `ascii' (G0) and `latin-iso8859-4' (G1) initially invoked.
-
-`iso-8859-5'
-`iso-8859-5-dos'
-`iso-8859-5-mac'
-`iso-8859-5-unix'
- Modeline indicator: `ISO8/Cyr'. A type `iso2022' coding system
- with `ascii' (G0) and `cyrillic-iso8859-5' (G1) initially invoked.
-
-`iso-8859-7'
-`iso-8859-7-dos'
-`iso-8859-7-mac'
-`iso-8859-7-unix'
- Modeline indicator: `Grk'. A type `iso2022' coding system with
- `ascii' (G0) and `greek-iso8859-7' (G1) initially invoked.
-
-`iso-8859-8'
-`iso-8859-8-dos'
-`iso-8859-8-mac'
-`iso-8859-8-unix'
- Modeline indicator: `MIME/Hbrw'. A type `iso2022' coding system
- with `ascii' (G0) and `hebrew-iso8859-8' (G1) initially invoked.
-
-`iso-8859-9'
-`iso-8859-9-dos'
-`iso-8859-9-mac'
-`iso-8859-9-unix'
- Modeline indicator: `MIME/Ltn-5'. A type `iso2022' coding system
- with `ascii' (G0) and `latin-iso8859-9' (G1) initially invoked.
-
-`koi8-r'
-`koi8-r-dos'
-`koi8-r-mac'
-`koi8-r-unix'
- Modeline indicator: `KOI8'. A type `ccl' coding-system used for
- KOI8-R, an encoding of the Cyrillic alphabet.
-
-`shift_jis'
-`shift_jis-dos'
-`shift_jis-mac'
-`shift_jis-unix'
- Modeline indicator: `Ja/SJIS'. A type `shift-jis' coding-system
- implementing the Shift-JIS encoding for Japanese. The underscore
- is to conform to the MIME charset implementing this encoding.
-
-`tis-620'
-`tis-620-dos'
-`tis-620-mac'
-`tis-620-unix'
- Modeline indicator: `TIS620'. A type `ccl' encoding for Thai. The
- external encoding is defined by TIS620, the internal encoding is
- peculiar to MULE, and called `thai-xtis'.
-
-`viqr'
- Modeline indicator: `VIQR'. A type `no-conversion' coding system
- with Unix EOL convention (ie, no conversion) using
- post-read-decode and pre-write-encode functions to translate the
- VIQR coding system for Vietnamese.
-
-`viscii'
-`viscii-dos'
-`viscii-mac'
-`viscii-unix'
- Modeline indicator: `VISCII'. A type `ccl' coding-system used for
- VISCII 1.1 for Vietnamese. Differs slightly from VSCII; VISCII is
- given priority by XEmacs.
-
-`vscii'
-`vscii-dos'
-`vscii-mac'
-`vscii-unix'
- Modeline indicator: `VSCII'. A type `ccl' coding-system used for
- VSCII 1.1 for Vietnamese. Differs slightly from VISCII, which is
- given priority by XEmacs. Use `(prefer-coding-system
- 'vietnamese-vscii)' to give priority to VSCII.
-
-\1f
-File: lispref.info, Node: CCL, Next: Category Tables, Prev: Coding Systems, Up: MULE
-
-CCL
-===
-
- CCL (Code Conversion Language) is a simple structured programming
-language designed for character coding conversions. A CCL program is
-compiled to CCL code (represented by a vector of integers) and executed
-by the CCL interpreter embedded in Emacs. The CCL interpreter
-implements a virtual machine with 8 registers called `r0', ..., `r7', a
-number of control structures, and some I/O operators. Take care when
-using registers `r0' (used in implicit "set" statements) and especially
-`r7' (used internally by several statements and operations, especially
-for multiple return values and I/O operations).
-
- CCL is used for code conversion during process I/O and file I/O for
-non-ISO2022 coding systems. (It is the only way for a user to specify a
-code conversion function.) It is also used for calculating the code
-point of an X11 font from a character code. However, since CCL is
-designed as a powerful programming language, it can be used for more
-generic calculation where efficiency is demanded. A combination of
-three or more arithmetic operations can be calculated faster by CCL than
-by Emacs Lisp.
-
- *Warning:* The code in `src/mule-ccl.c' and
-`$packages/lisp/mule-base/mule-ccl.el' is the definitive description of
-CCL's semantics. The previous version of this section contained
-several typos and obsolete names left from earlier versions of MULE,
-and many may remain. (I am not an experienced CCL programmer; the few
-who know CCL well find writing English painful.)
-
- A CCL program transforms an input data stream into an output data
-stream. The input stream, held in a buffer of constant bytes, is left
-unchanged. The buffer may be filled by an external input operation,
-taken from an Emacs buffer, or taken from a Lisp string. The output
-buffer is a dynamic array of bytes, which can be written by an external
-output operation, inserted into an Emacs buffer, or returned as a Lisp
-string.
-
- A CCL program is a (Lisp) list containing two or three members. The
-first member is the "buffer magnification", which indicates the
-required minimum size of the output buffer as a multiple of the input
-buffer. It is followed by the "main block" which executes while there
-is input remaining, and an optional "EOF block" which is executed when
-the input is exhausted. Both the main block and the EOF block are CCL
-blocks.
-
- A "CCL block" is either a CCL statement or list of CCL statements.
-A "CCL statement" is either a "set statement" (either an integer or an
-"assignment", which is a list of a register to receive the assignment,
-an assignment operator, and an expression) or a "control statement" (a
-list starting with a keyword, whose allowable syntax depends on the
-keyword).
-
-* Menu:
-
-* CCL Syntax:: CCL program syntax in BNF notation.
-* CCL Statements:: Semantics of CCL statements.
-* CCL Expressions:: Operators and expressions in CCL.
-* Calling CCL:: Running CCL programs.
-* CCL Examples:: The encoding functions for Big5 and KOI-8.
-
-\1f
-File: lispref.info, Node: CCL Syntax, Next: CCL Statements, Up: CCL
-
-CCL Syntax
-----------
-
- The full syntax of a CCL program in BNF notation:
-
-CCL_PROGRAM :=
- (BUFFER_MAGNIFICATION
- CCL_MAIN_BLOCK
- [ CCL_EOF_BLOCK ])
-
-BUFFER_MAGNIFICATION := integer
-CCL_MAIN_BLOCK := CCL_BLOCK
-CCL_EOF_BLOCK := CCL_BLOCK
-
-CCL_BLOCK :=
- STATEMENT | (STATEMENT [STATEMENT ...])
-STATEMENT :=
- SET | IF | BRANCH | LOOP | REPEAT | BREAK | READ | WRITE
- | CALL | END
-
-SET :=
- (REG = EXPRESSION)
- | (REG ASSIGNMENT_OPERATOR EXPRESSION)
- | integer
-
-EXPRESSION := ARG | (EXPRESSION OPERATOR ARG)
-
-IF := (if EXPRESSION CCL_BLOCK [CCL_BLOCK])
-BRANCH := (branch EXPRESSION CCL_BLOCK [CCL_BLOCK ...])
-LOOP := (loop STATEMENT [STATEMENT ...])
-BREAK := (break)
-REPEAT :=
- (repeat)
- | (write-repeat [REG | integer | string])
- | (write-read-repeat REG [integer | ARRAY])
-READ :=
- (read REG ...)
- | (read-if (REG OPERATOR ARG) CCL_BLOCK CCL_BLOCK)
- | (read-branch REG CCL_BLOCK [CCL_BLOCK ...])
-WRITE :=
- (write REG ...)
- | (write EXPRESSION)
- | (write integer) | (write string) | (write REG ARRAY)
- | string
-CALL := (call ccl-program-name)
-END := (end)
-
-REG := r0 | r1 | r2 | r3 | r4 | r5 | r6 | r7
-ARG := REG | integer
-OPERATOR :=
- + | - | * | / | % | & | '|' | ^ | << | >> | <8 | >8 | //
- | < | > | == | <= | >= | != | de-sjis | en-sjis
-ASSIGNMENT_OPERATOR :=
- += | -= | *= | /= | %= | &= | '|=' | ^= | <<= | >>=
-ARRAY := '[' integer ... ']'
-
-\1f
-File: lispref.info, Node: CCL Statements, Next: CCL Expressions, Prev: CCL Syntax, Up: CCL
-
-CCL Statements
---------------
-
- The Emacs Code Conversion Language provides the following statement
-types: "set", "if", "branch", "loop", "repeat", "break", "read",
-"write", "call", and "end".
-
-Set statement:
-==============
-
- The "set" statement has three variants with the syntaxes `(REG =
-EXPRESSION)', `(REG ASSIGNMENT_OPERATOR EXPRESSION)', and `INTEGER'.
-The assignment operator variation of the "set" statement works the same
-way as the corresponding C expression statement does. The assignment
-operators are `+=', `-=', `*=', `/=', `%=', `&=', `|=', `^=', `<<=',
-and `>>=', and they have the same meanings as in C. A "naked integer"
-INTEGER is equivalent to a SET statement of the form `(r0 = INTEGER)'.
-
-I/O statements:
-===============
-
- The "read" statement takes one or more registers as arguments. It
-reads one byte (a C char) from the input into each register in turn.
-
- The "write" takes several forms. In the form `(write REG ...)' it
-takes one or more registers as arguments and writes each in turn to the
-output. The integer in a register (interpreted as an Emchar) is
-encoded to multibyte form (ie, Bufbytes) and written to the current
-output buffer. If it is less than 256, it is written as is. The forms
-`(write EXPRESSION)' and `(write INTEGER)' are treated analogously.
-The form `(write STRING)' writes the constant string to the output. A
-"naked string" `STRING' is equivalent to the statement `(write
-STRING)'. The form `(write REG ARRAY)' writes the REGth element of the
-ARRAY to the output.
-
-Conditional statements:
-=======================
-
- The "if" statement takes an EXPRESSION, a CCL BLOCK, and an optional
-SECOND CCL BLOCK as arguments. If the EXPRESSION evaluates to
-non-zero, the first CCL BLOCK is executed. Otherwise, if there is a
-SECOND CCL BLOCK, it is executed.
-
- The "read-if" variant of the "if" statement takes an EXPRESSION, a
-CCL BLOCK, and an optional SECOND CCL BLOCK as arguments. The
-EXPRESSION must have the form `(REG OPERATOR OPERAND)' (where OPERAND is
-a register or an integer). The `read-if' statement first reads from
-the input into the first register operand in the EXPRESSION, then
-conditionally executes a CCL block just as the `if' statement does.
-
- The "branch" statement takes an EXPRESSION and one or more CCL
-blocks as arguments. The CCL blocks are treated as a zero-indexed
-array, and the `branch' statement uses the EXPRESSION as the index of
-the CCL block to execute. Null CCL blocks may be used as no-ops,
-continuing execution with the statement following the `branch'
-statement in the containing CCL block. Out-of-range values for the
-EXPRESSION are also treated as no-ops.
-
- The "read-branch" variant of the "branch" statement takes an
-REGISTER, a CCL BLOCK, and an optional SECOND CCL BLOCK as arguments.
-The `read-branch' statement first reads from the input into the
-REGISTER, then conditionally executes a CCL block just as the `branch'
-statement does.
-
-Loop control statements:
-========================
-
- The "loop" statement creates a block with an implied jump from the
-end of the block back to its head. The loop is exited on a `break'
-statement, and continued without executing the tail by a `repeat'
-statement.
-
- The "break" statement, written `(break)', terminates the current
-loop and continues with the next statement in the current block.
-
- The "repeat" statement has three variants, `repeat', `write-repeat',
-and `write-read-repeat'. Each continues the current loop from its
-head, possibly after performing I/O. `repeat' takes no arguments and
-does no I/O before jumping. `write-repeat' takes a single argument (a
-register, an integer, or a string), writes it to the output, then jumps.
-`write-read-repeat' takes one or two arguments. The first must be a
-register. The second may be an integer or an array; if absent, it is
-implicitly set to the first (register) argument. `write-read-repeat'
-writes its second argument to the output, then reads from the input
-into the register, and finally jumps. See the `write' and `read'
-statements for the semantics of the I/O operations for each type of
-argument.
-
-Other control statements:
-=========================
-
- The "call" statement, written `(call CCL-PROGRAM-NAME)', executes a
-CCL program as a subroutine. It does not return a value to the caller,
-but can modify the register status.
-
- The "end" statement, written `(end)', terminates the CCL program
-successfully, and returns to caller (which may be a CCL program). It
-does not alter the status of the registers.
-