Ubuntu Manpage: Code_Conversion - Coding system objects and API for them.

NAME

       Code_Conversion - Coding system objects and API for them.

   Data Structures
       struct MConverter
           Structure to be used in code conversion.
       struct MCodingInfoISO2022
           Structure for a coding system of type MCODING_TYPE_ISO_2022.
       struct MCodingInfoUTF
           Structure for extra information about a coding system of type MCODING_TYPE_UTF.

   Enumerations
       enum MConversionResult { MCONVERSION_RESULT_SUCCESS, MCONVERSION_RESULT_INVALID_BYTE,
           MCONVERSION_RESULT_INVALID_CHAR, MCONVERSION_RESULT_INSUFFICIENT_SRC,
           MCONVERSION_RESULT_INSUFFICIENT_DST, MCONVERSION_RESULT_IO_ERROR }
           Codes that represent the result of code conversion.
       enum MCodingType { MCODING_TYPE_CHARSET, MCODING_TYPE_UTF, MCODING_TYPE_ISO_2022,
           MCODING_TYPE_MISC }
           Types of coding system.
       enum MCodingFlagISO2022 { MCODING_ISO_RESET_AT_EOL =  0x1, MCODING_ISO_RESET_AT_CNTL =
           0x2, MCODING_ISO_EIGHT_BIT =  0x4, MCODING_ISO_LONG_FORM =  0x8,
           MCODING_ISO_DESIGNATION_G0 =  0x10, MCODING_ISO_DESIGNATION_G1 =  0x20,
           MCODING_ISO_DESIGNATION_CTEXT =  0x40, MCODING_ISO_DESIGNATION_CTEXT_EXT =  0x80,
           MCODING_ISO_LOCKING_SHIFT =  0x100, MCODING_ISO_SINGLE_SHIFT =  0x200,
           MCODING_ISO_SINGLE_SHIFT_7 =  0x400, MCODING_ISO_EUC_TW_SHIFT =  0x800,
           MCODING_ISO_ISO6429 =  0x1000, MCODING_ISO_REVISION_NUMBER =  0x2000,
           MCODING_ISO_FULL_SUPPORT =  0x3000, MCODING_ISO_FLAG_MAX }
           Bit-masks to specify the detail of coding system whose type is MCODING_TYPE_ISO_2022.

   Functions
       MSymbol mconv_define_coding (const char *name, MPlist *plist, int(*resetter)(MConverter
           *), int(*decoder)(const unsigned char *, int, MText *, MConverter *),
           int(*encoder)(MText *, int, int, unsigned char *, int, MConverter *), void
           *extra_info)
           Define a coding system.
       MSymbol mconv_resolve_coding (MSymbol symbol)
           Resolve coding system name.
       int mconv_list_codings (MSymbol **symbols)
           List symbols representing coding systems.
       MConverter * mconv_buffer_converter (MSymbol name, const unsigned char *buf, int n)
           Create a code converter bound to a buffer.
       MConverter * mconv_stream_converter (MSymbol name, FILE *fp)
           Create a code converter bound to a stream.
       int mconv_reset_converter (MConverter *converter)
           Reset a code converter.
       void mconv_free_converter (MConverter *converter)
           Free a code converter.
       MConverter * mconv_rebind_buffer (MConverter *converter, const unsigned char *buf, int n)
           Bind a buffer to a code converter.
       MConverter * mconv_rebind_stream (MConverter *converter, FILE *fp)
           Bind a stream to a code converter.
       MText * mconv_decode (MConverter *converter, MText *mt)
           Decode a byte sequence into an M-text.
       MText * mconv_decode_buffer (MSymbol name, const unsigned char *buf, int n)
           Decode a buffer area based on a coding system.
       MText * mconv_decode_stream (MSymbol name, FILE *fp)
           Decode a stream input based on a coding system.
       int mconv_encode (MConverter *converter, MText *mt)
           Encode an M-text into a byte sequence.
       int mconv_encode_range (MConverter *converter, MText *mt, int from, int to)
           Encode a part of an M-text.
       int mconv_encode_buffer (MSymbol name, MText *mt, unsigned char *buf, int n)
           Encode an M-text into a buffer area.
       int mconv_encode_stream (MSymbol name, MText *mt, FILE *fp)
           Encode an M-text to write to a stream.
       int mconv_getc (MConverter *converter)
           Read a character via a code converter.
       int mconv_ungetc (MConverter *converter, int c)
           Push a character back to a code converter.
       int mconv_putc (MConverter *converter, int c)
           Write a character via a code converter.
       MText * mconv_gets (MConverter *converter, MText *mt)
           Read a line using a code converter.

   Variables: Symbols representing coding systems
       MSymbol Mcoding_us_ascii
           Symbol for the coding system US-ASCII.
       MSymbol Mcoding_iso_8859_1
           Symbol for the coding system ISO-8859-1.
       MSymbol Mcoding_utf_8
           Symbol for the coding system UTF-8.
       MSymbol Mcoding_utf_8_full
           Symbol for the coding system UTF-8-FULL.
       MSymbol Mcoding_utf_16
           Symbol for the coding system UTF-16.
       MSymbol Mcoding_utf_16be
           Symbol for the coding system UTF-16BE.
       MSymbol Mcoding_utf_16le
           Symbol for the coding system UTF-16LE.
       MSymbol Mcoding_utf_32
           Symbol for the coding system UTF-32.
       MSymbol Mcoding_utf_32be
           Symbol for the coding system UTF-32BE.
       MSymbol Mcoding_utf_32le
           Symbol for the coding system UTF-32LE.
       MSymbol Mcoding_sjis
           Symbol for the coding system SJIS.

   Variables: Parameter keys for mconv_define_coding().
       MSymbol Mtype
       MSymbol Mcharsets
       MSymbol Mflags
       MSymbol Mdesignation
       MSymbol Minvocation
       MSymbol Mcode_unit
       MSymbol Mbom
       MSymbol Mlittle_endian

   Variables: Symbols representing coding system types.
       MSymbol Mutf
       MSymbol Miso_2022

   Variables: Symbols appearing in the value of Mflags parameter.
        Symbols that can be a value of the Mflags parameter of a coding system used in an
       argument to the mconv_define_coding() function (which see).
       MSymbol Mreset_at_eol
       MSymbol Mreset_at_cntl
       MSymbol Meight_bit
       MSymbol Mlong_form
       MSymbol Mdesignation_g0
       MSymbol Mdesignation_g1
       MSymbol Mdesignation_ctext
       MSymbol Mdesignation_ctext_ext
       MSymbol Mlocking_shift
       MSymbol Msingle_shift
       MSymbol Msingle_shift_7
       MSymbol Meuc_tw_shift
       MSymbol Miso_6429
       MSymbol Mrevision_number
       MSymbol Mfull_support

   Variables: Others
        Remaining variables.
       MSymbol Mmaybe
           Symbol whose name is 'maybe'.
       MSymbol Mcoding
           The symbol Mcoding.

Detailed Description

       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.

Data Structure Documentation

MConverter
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

MCodingInfoISO2022
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

MCodingInfoUTF
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.

Enumeration Type Documentation

enum MConversionResult
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.

enum MCodingType
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.

enum MCodingFlagISO2022
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

Variable Documentation

MSymbol Mcoding_us_ascii
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.

MSymbol Mcoding_iso_8859_1
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.

MSymbol Mcoding_utf_8
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.

MSymbol Mcoding_utf_8_full
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.

MSymbol Mcoding_utf_16
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).

MSymbol Mcoding_utf_16be
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).

MSymbol Mcoding_utf_16le
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).

MSymbol Mcoding_utf_32
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).

MSymbol Mcoding_utf_32be
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).

MSymbol Mcoding_utf_32le
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).

MSymbol Mcoding_sjis
Symbol for the coding system SJIS. The symbol Mcoding_sjis has name 'sjis' and represents
a coding system for the CES Shift-JIS.

MSymbol Mtype Parameter key for mconv_define_coding() (which see).
MSymbol Mcharsets
MSymbol Mflags
MSymbol Mdesignation
MSymbol Minvocation
MSymbol Mcode_unit
MSymbol Mbom
MSymbol Mlittle_endian
MSymbol Mutf Symbol that can be a value of the Mtype parameter of a coding system used in an
argument to the mconv_define_coding() function (which see).
MSymbol Miso_2022
MSymbol Mreset_at_eol
MSymbol Mreset_at_cntl
MSymbol Meight_bit
MSymbol Mlong_form
MSymbol Mdesignation_g0
MSymbol Mdesignation_g1
MSymbol Mdesignation_ctext
MSymbol Mdesignation_ctext_ext
MSymbol Mlocking_shift
MSymbol Msingle_shift
MSymbol Msingle_shift_7
MSymbol Meuc_tw_shift
MSymbol Miso_6429
MSymbol Mrevision_number
MSymbol Mfull_support
MSymbol Mmaybe
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).

MSymbol Mcoding
The symbol Mcoding. Any decoded M-text has a text property whose key is the predefined
symbol Mcoding. The name of Mcoding is 'coding'.

Author

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COPYRIGHT

       Copyright (C) 2001 Information-technology Promotion Agency (IPA)
       Copyright (C) 2001-2011 National Institute of Advanced Industrial Science and Technology
       (AIST)
       Permission is granted to copy, distribute and/or modify this document under the terms of
       the GNU Free Documentation License <http://www.gnu.org/licenses/fdl.html>.