Coding system objects and api for them.
Coding system objects and API for them.
The m17n library represents a character encoding scheme (CES) of coded character sets (CCS) as an object called coding system. Application programs can add original coding systems.
To encode means converting code-points to character codes and to decode means converting character codes back to code-points.
Application programs can decode a byte sequence with a specified coding system into an M-text, and inversely, can encode an M-text into a byte sequence.
FIELD DOCUMENTATION:
int MConverter::lenient
If the conversion is strict, the converter stops at the first invalid byte (on decoding) or at the first character not supported by the coding system (on encoding). If this happens, MConverter->result is set to MCONVERSION_RESULT_INVALID_BYTE or MCONVERSION_RESULT_INVALID_CHAR accordingly.
If the conversion is lenient, on decoding, an invalid byte is kept per se, and on encoding, an invalid character is replaced with '<U+XXXX>' (if the character is a Unicode character) or with '<M+XXXXXX>' (otherwise).
int MConverter::last_block
On decoding, in the case that the last few bytes are too short to form a valid byte sequence:
If the value is nonzero, the conversion terminates by error (MCONVERSION_RESULT_INVALID_BYTE) at the first byte of the sequence.
If the value is zero, the conversion terminates successfully. Those bytes are stored in the converter as carryover and are prepended to the byte sequence of the further conversion.
On encoding, in the case that the coding system is context dependent:
If the value is nonzero, the conversion may produce a byte sequence at the end to reset the context to the initial state even if the source characters are zero.
If the value is zero, the conversion never produce such a byte sequence at the end.
unsigned MConverter::at_most
int MConverter::nchars
Number of characters most recently decoded or encoded.
int MConverter::nbytes
enum MConversionResult MConverter::result
void* MConverter::ptr
double MConverter::dbl
char MConverter::c[256]
union { ... } MConverter::status
void* MConverter::internal_info
FIELD DOCUMENTATION:
int MCodingInfoISO2022::initial_invocation[2]
char MCodingInfoISO2022::designations[32]
If an element value is 0..3, it specifies a graphic register number to designate the corresponds charset. In addition, the charset is initially designated to that graphic register.
If the value is -4..-1, it specifies a graphic register number 0..3 respectively to designate the corresponds charset. Initially, the charset is not designated to any graphic register.
unsigned MCodingInfoISO2022::flags
FIELD DOCUMENTATION:
int MCodingInfoUTF::code_unit_bits
int MCodingInfoUTF::bom
0: On decoding, check the first two byte. If they are BOM, decide endian by them. If not, decide endian by the member endian. On encoding, produce byte sequence according to endian with heading BOM.
1: On decoding, do not handle the first two bytes as BOM, and decide endian by endian. On encoding, produce byte sequence according to endian without BOM.
2: On decoding, handle the first two bytes as BOM and decide ending by them. On encoding, produce byte sequence according to endian with heading BOM.
If <code_unit_bits> is 8, the value has no meaning.
int MCodingInfoUTF::endian
If <code_unit_bits> is 8, the value has no meaning.
Codes that represent the result of code conversion. One of these values is set in MConverter->result.
Enumerator:
MCONVERSION_RESULT_SUCCESS
Code conversion is successful.
MCONVERSION_RESULT_INVALID_BYTE
On decoding, the source contains an invalid byte.
MCONVERSION_RESULT_INVALID_CHAR
On encoding, the source contains a character that cannot be encoded by the specified coding system.
MCONVERSION_RESULT_INSUFFICIENT_SRC
On decoding, the source ends with an incomplete byte sequence.
MCONVERSION_RESULT_INSUFFICIENT_DST
On encoding, the destination is too short to store the result.
MCONVERSION_RESULT_IO_ERROR
An I/O error occurred in the conversion.
Types of coding system.
Enumerator:
MCODING_TYPE_CHARSET
A coding system of this type supports charsets directly. The dimension of each charset defines the length of bytes to represent a single character of the charset, and a byte sequence directly represents the code-point of a character. The m17n library provides the default decoding and encoding routines of this type.
MCODING_TYPE_UTF
A coding system of this type supports byte sequences of a UTF (UTF-8, UTF-16, UTF-32) like structure. The m17n library provides the default decoding and encoding routines of this type.
MCODING_TYPE_ISO_2022
A coding system of this type supports byte sequences of an ISO-2022 like structure. The details of each structure are specified by MCodingInfoISO2022. The m17n library provides decoding and encoding routines of this type.
MCODING_TYPE_MISC
A coding system of this type is for byte sequences of miscellaneous structures. The m17n library does not provide decoding and encoding routines of this type. They must be provided by the application program.
Bit-masks to specify the detail of coding system whose type is MCODING_TYPE_ISO_2022.
Enumerator:
MCODING_ISO_RESET_AT_EOL
On encoding, reset the invocation and designation status to initial at end of line.
MCODING_ISO_RESET_AT_CNTL
On encoding, reset the invocation and designation status to initial before any control codes.
MCODING_ISO_EIGHT_BIT
Use the right graphic plane.
MCODING_ISO_LONG_FORM
Use the non-standard 4 bytes format for designation sequence for charsets JISX0208-1978, GB2312, and JISX0208-1983.
MCODING_ISO_DESIGNATION_G0
On encoding, unless explicitly specified, designate charsets to G0.
MCODING_ISO_DESIGNATION_G1
On encoding, unless explicitly specified, designate charsets except for ASCII to G1.
MCODING_ISO_DESIGNATION_CTEXT
On encoding, unless explicitly specified, designate 94-chars charsets to G0, 96-chars charsets to G1.
MCODING_ISO_DESIGNATION_CTEXT_EXT
On encoding, encode such charsets not conforming to ISO-2022 by ESC % / ..., and encode non-supported Unicode characters by ESC % G ... ESC % @ . On decoding, handle those escape sequences.
MCODING_ISO_LOCKING_SHIFT
Use locking shift.
MCODING_ISO_SINGLE_SHIFT
Use single shift (SS2 (0x8E or ESC N), SS3 (0x8F or ESC O)).
MCODING_ISO_SINGLE_SHIFT_7
Use 7-bit single shift 2 (SS2 (0x19)).
MCODING_ISO_EUC_TW_SHIFT
Use EUC-TW like special shifting.
MCODING_ISO_ISO6429
Use ISO-6429 escape sequences to indicate direction. Not yet implemented.
MCODING_ISO_REVISION_NUMBER
On encoding, if a charset has revision number, produce escape sequences to specify the number.
MCODING_ISO_FULL_SUPPORT
Support all ISO-2022 charsets.
MCODING_ISO_FLAG_MAX
Symbol for the coding system US-ASCII. The symbol Mcoding_us_ascii has name 'us-ascii' and represents a coding system for the CES US-ASCII.
Symbol for the coding system ISO-8859-1. The symbol Mcoding_iso_8859_1 has name 'iso-8859-1' and represents a coding system for the CES ISO-8859-1.
Symbol for the coding system UTF-8. The symbol Mcoding_utf_8 has name 'utf-8' and represents a coding system for the CES UTF-8.
Symbol for the coding system UTF-8-FULL. The symbol Mcoding_utf_8_full has name 'utf-8-full' and represents a coding system that is a extension of UTF-8. This coding system uses the same encoding algorithm as UTF-8 but is not limited to the Unicode characters. It can encode all characters supported by the m17n library.
Symbol for the coding system UTF-16. The symbol Mcoding_utf_16 has name 'utf-16' and represents a coding system for the CES UTF-16 (RFC 2279).
Symbol for the coding system UTF-16BE. The symbol Mcoding_utf_16be has name 'utf-16be' and represents a coding system for the CES UTF-16BE (RFC 2279).
Symbol for the coding system UTF-16LE. The symbol Mcoding_utf_16le has name 'utf-16le' and represents a coding system for the CES UTF-16LE (RFC 2279).
Symbol for the coding system UTF-32. The symbol Mcoding_utf_32 has name 'utf-32' and represents a coding system for the CES UTF-32 (RFC 2279).
Symbol for the coding system UTF-32BE. The symbol Mcoding_utf_32be has name 'utf-32be' and represents a coding system for the CES UTF-32BE (RFC 2279).
Symbol for the coding system UTF-32LE. The symbol Mcoding_utf_32le has name 'utf-32le' and represents a coding system for the CES UTF-32LE (RFC 2279).
Symbol for the coding system SJIS. The symbol Mcoding_sjis has name 'sjis' and represents a coding system for the CES Shift-JIS.
Symbol whose name is 'maybe'. The variable Mmaybe is a symbol of name 'maybe'. It is used a value of Mbom parameter of the function mconv_define_coding() (which see).
The symbol Mcoding. Any decoded M-text has a text property whose key is the predefined symbol Mcoding. The name of Mcoding is 'coding'.
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Copyright (C) 2001-2011 National Institute of Advanced Industrial Science and Technology (AIST)
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