encoding: interface for the encoding conversion functions

## encoding

encoding - interface for the encoding conversion functions

interface for the encoding conversion functions needed for XML basic encoding and iconv() support. Related specs are rfc2044 (UTF-8 and UTF-16) F. Yergeau Alis Technologies [ISO-10646] UTF-8 and UTF-16 in Annexes [ISO-8859-1] ISO Latin-1 characters codes. [UNICODE] The Unicode Consortium, "The Unicode Standard -- Worldwide Character Encoding -- Version 1.0", Addison- Wesley, Volume 1, 1991, Volume 2, 1992. UTF-8 is described in Unicode Technical Report #4. [US-ASCII] Coded Character Set--7-bit American Standard Code for Information Interchange, ANSI X3.4-1986.

Author(s): Daniel Veillard

## Synopsis

    typedef struct _uconv_t uconv_t;
    typedef enum xmlCharEncoding;
    typedef struct _xmlCharEncodingHandler xmlCharEncodingHandler;
    typedef xmlCharEncodingHandler * xmlCharEncodingHandlerPtr;
    int	xmlDelEncodingAlias		(const char * alias);
    const char *	xmlGetEncodingAlias	(const char * alias);
    void	xmlRegisterCharEncodingHandler	(xmlCharEncodingHandlerPtr handler);
    int	UTF8Toisolat1			(unsigned char * out,
    					 int * outlen,
    					 const unsigned char * in,
    					 int * inlen);
    void	xmlInitCharEncodingHandlers	(void);
    int	xmlAddEncodingAlias		(const char * name,
    					 const char * alias);
    void	xmlCleanupEncodingAliases	(void);
    int	xmlCharEncOutFunc		(xmlCharEncodingHandler * handler,
    					 xmlBufferPtr out,
    					 xmlBufferPtr in);
    xmlCharEncoding	xmlParseCharEncoding	(const char * name);
    typedef int xmlCharEncodingInputFunc	(unsigned char * out,
    					 int * outlen,
    					 const unsigned char * in,
    					 int * inlen);
    void	xmlCleanupCharEncodingHandlers	(void);
    xmlCharEncodingHandlerPtr	xmlNewCharEncodingHandler	(const char * name,
    							 xmlCharEncodingInputFunc input,
    							 xmlCharEncodingOutputFunc output);
    typedef int xmlCharEncodingOutputFunc	(unsigned char * out,
    					 int * outlen,
    					 const unsigned char * in,
    					 int * inlen);
    int	isolat1ToUTF8			(unsigned char * out,
    					 int * outlen,
    					 const unsigned char * in,
    					 int * inlen);
    xmlCharEncodingHandlerPtr	xmlFindCharEncodingHandler	(const char * name);
    int	xmlCharEncInFunc		(xmlCharEncodingHandler * handler,
    					 xmlBufferPtr out,
    					 xmlBufferPtr in);
    xmlCharEncodingHandlerPtr	xmlGetCharEncodingHandler	(xmlCharEncoding enc);
    int	xmlCharEncFirstLine		(xmlCharEncodingHandler * handler,
    					 xmlBufferPtr out,
    					 xmlBufferPtr in);
    xmlCharEncoding	xmlDetectCharEncoding	(const unsigned char * in,
    					 int len);
    int	xmlCharEncCloseFunc		(xmlCharEncodingHandler * handler);
    const char *	xmlGetCharEncodingName	(xmlCharEncoding enc);

## Description

## Details

### Structure uconv_t

    struct _uconv_t {
        UConverter *	uconv	: for conversion between an encoding and UTF-16
        UConverter *	utf8	: for conversion between UTF-8 and UTF-16
    } uconv_t;

### Enum xmlCharEncoding

    enum xmlCharEncoding {
        XML_CHAR_ENCODING_ERROR = -1 /* No char encoding detected */
        XML_CHAR_ENCODING_NONE = 0 /* No char encoding detected */
        XML_CHAR_ENCODING_UTF8 = 1 /* UTF-8 */
        XML_CHAR_ENCODING_UTF16LE = 2 /* UTF-16 little endian */
        XML_CHAR_ENCODING_UTF16BE = 3 /* UTF-16 big endian */
        XML_CHAR_ENCODING_UCS4LE = 4 /* UCS-4 little endian */
        XML_CHAR_ENCODING_UCS4BE = 5 /* UCS-4 big endian */
        XML_CHAR_ENCODING_EBCDIC = 6 /* EBCDIC uh! */
        XML_CHAR_ENCODING_UCS4_2143 = 7 /* UCS-4 unusual ordering */
        XML_CHAR_ENCODING_UCS4_3412 = 8 /* UCS-4 unusual ordering */
        XML_CHAR_ENCODING_UCS2 = 9 /* UCS-2 */
        XML_CHAR_ENCODING_8859_1 = 10 /* ISO-8859-1 ISO Latin 1 */
        XML_CHAR_ENCODING_8859_2 = 11 /* ISO-8859-2 ISO Latin 2 */
        XML_CHAR_ENCODING_8859_3 = 12 /* ISO-8859-3 */
        XML_CHAR_ENCODING_8859_4 = 13 /* ISO-8859-4 */
        XML_CHAR_ENCODING_8859_5 = 14 /* ISO-8859-5 */
        XML_CHAR_ENCODING_8859_6 = 15 /* ISO-8859-6 */
        XML_CHAR_ENCODING_8859_7 = 16 /* ISO-8859-7 */
        XML_CHAR_ENCODING_8859_8 = 17 /* ISO-8859-8 */
        XML_CHAR_ENCODING_8859_9 = 18 /* ISO-8859-9 */
        XML_CHAR_ENCODING_2022_JP = 19 /* ISO-2022-JP */
        XML_CHAR_ENCODING_SHIFT_JIS = 20 /* Shift_JIS */
        XML_CHAR_ENCODING_EUC_JP = 21 /* EUC-JP */
        XML_CHAR_ENCODING_ASCII = 22 /*  pure ASCII */
    };

### Structure xmlCharEncodingHandler

    struct _xmlCharEncodingHandler {
        char *	name
        xmlCharEncodingInputFunc	input
        xmlCharEncodingOutputFunc	output
        iconv_t	iconv_in
        iconv_t	iconv_out
        uconv_t *	uconv_in
        uconv_t *	uconv_out
    } xmlCharEncodingHandler;

### Typedef xmlCharEncodingHandlerPtr

    xmlCharEncodingHandler * xmlCharEncodingHandlerPtr;

### Function type xmlCharEncodingInputFunc

    int	xmlCharEncodingInputFunc	(unsigned char * out,
    					 int * outlen,
    					 const unsigned char * in,
    					 int * inlen)

Take a block of chars in the original encoding and try to convert it to an UTF-8 block of chars out.

`out`: | a pointer to an array of bytes to store the UTF-8 result
`outlen`: | the length of @out
`in`: | a pointer to an array of chars in the original encoding
`inlen`: | the length of @in
`Returns`: | the number of bytes written, -1 if lack of space, or -2 if the transcoding failed. The value of @inlen after return is the number of octets consumed if the return value is positive, else unpredictiable. The value of @outlen after return is the number of octets consumed.

### Function type xmlCharEncodingOutputFunc

    int	xmlCharEncodingOutputFunc	(unsigned char * out,
    					 int * outlen,
    					 const unsigned char * in,
    					 int * inlen)

Take a block of UTF-8 chars in and try to convert it to another encoding. Note: a first call designed to produce heading info is called with in = NULL. If stateful this should also initialize the encoder state.

`out`: | a pointer to an array of bytes to store the result
`outlen`: | the length of @out
`in`: | a pointer to an array of UTF-8 chars
`inlen`: | the length of @in
`Returns`: | the number of bytes written, -1 if lack of space, or -2 if the transcoding failed. The value of @inlen after return is the number of octets consumed if the return value is positive, else unpredictiable. The value of @outlen after return is the number of octets produced.

### UTF8Toisolat1 ()

    int	UTF8Toisolat1			(unsigned char * out,
    					 int * outlen,
    					 const unsigned char * in,
    					 int * inlen)

Take a block of UTF-8 chars in and try to convert it to an ISO Latin 1 block of chars out.

`out`: | a pointer to an array of bytes to store the result
`outlen`: | the length of @out
`in`: | a pointer to an array of UTF-8 chars
`inlen`: | the length of @in
`Returns`: | the number of bytes written if success, -2 if the transcoding fails, or -1 otherwise The value of @inlen after return is the number of octets consumed if the return value is positive, else unpredictable. The value of @outlen after return is the number of octets consumed.

### isolat1ToUTF8 ()

    int	isolat1ToUTF8			(unsigned char * out,
    					 int * outlen,
    					 const unsigned char * in,
    					 int * inlen)

Take a block of ISO Latin 1 chars in and try to convert it to an UTF-8 block of chars out.

`out`: | a pointer to an array of bytes to store the result
`outlen`: | the length of @out
`in`: | a pointer to an array of ISO Latin 1 chars
`inlen`: | the length of @in
`Returns`: | the number of bytes written if success, or -1 otherwise The value of @inlen after return is the number of octets consumed if the return value is positive, else unpredictable. The value of @outlen after return is the number of octets consumed.

### xmlAddEncodingAlias ()

    int	xmlAddEncodingAlias		(const char * name,
    					 const char * alias)

Registers an alias @alias for an encoding named @name. Existing alias will be overwritten.

`name`: | the encoding name as parsed, in UTF-8 format (ASCII actually)
`alias`: | the alias name as parsed, in UTF-8 format (ASCII actually)
`Returns`: | 0 in case of success, -1 in case of error

### xmlCharEncCloseFunc ()

    int	xmlCharEncCloseFunc		(xmlCharEncodingHandler * handler)

Generic front-end for encoding handler close function

`handler`: | char enconding transformation data structure
`Returns`: | 0 if success, or -1 in case of error

### xmlCharEncFirstLine ()

    int	xmlCharEncFirstLine		(xmlCharEncodingHandler * handler,
    					 xmlBufferPtr out,
    					 xmlBufferPtr in)

Front-end for the encoding handler input function, but handle only the very first line, i.e. limit itself to 45 chars.

`handler`: | char enconding transformation data structure
`out`: | an xmlBuffer for the output.
`in`: | an xmlBuffer for the input
`Returns`: | the number of byte written if success, or -1 general error -2 if the transcoding fails (for *in is not valid utf8 string or the result of transformation can't fit into the encoding we want), or

### xmlCharEncInFunc ()

    int	xmlCharEncInFunc		(xmlCharEncodingHandler * handler,
    					 xmlBufferPtr out,
    					 xmlBufferPtr in)

Generic front-end for the encoding handler input function

`handler`: | char encoding transformation data structure
`out`: | an xmlBuffer for the output.
`in`: | an xmlBuffer for the input
`Returns`: | the number of byte written if success, or -1 general error -2 if the transcoding fails (for *in is not valid utf8 string or the result of transformation can't fit into the encoding we want), or

### xmlCharEncOutFunc ()

    int	xmlCharEncOutFunc		(xmlCharEncodingHandler * handler,
    					 xmlBufferPtr out,
    					 xmlBufferPtr in)

Generic front-end for the encoding handler output function a first call with @in == NULL has to be made firs to initiate the output in case of non-stateless encoding needing to initiate their state or the output (like the BOM in UTF16). In case of UTF8 sequence conversion errors for the given encoder, the content will be automatically remapped to a CharRef sequence.

`handler`: | char enconding transformation data structure
`out`: | an xmlBuffer for the output.
`in`: | an xmlBuffer for the input
`Returns`: | the number of byte written if success, or -1 general error -2 if the transcoding fails (for *in is not valid utf8 string or the result of transformation can't fit into the encoding we want), or

### xmlCleanupCharEncodingHandlers ()

    void	xmlCleanupCharEncodingHandlers	(void)

Cleanup the memory allocated for the char encoding support, it unregisters all the encoding handlers and the aliases.

### xmlCleanupEncodingAliases ()

    void	xmlCleanupEncodingAliases	(void)

Unregisters all aliases

### xmlDelEncodingAlias ()

    int	xmlDelEncodingAlias		(const char * alias)

Unregisters an encoding alias @alias

`alias`: | the alias name as parsed, in UTF-8 format (ASCII actually)
`Returns`: | 0 in case of success, -1 in case of error

### xmlDetectCharEncoding ()

    xmlCharEncoding	xmlDetectCharEncoding	(const unsigned char * in,
    					 int len)

Guess the encoding of the entity using the first bytes of the entity content according to the non-normative appendix F of the XML-1.0 recommendation.

`in`: | a pointer to the first bytes of the XML entity, must be at least 2 bytes long (at least 4 if encoding is UTF4 variant).
`len`: | pointer to the length of the buffer
`Returns`: | one of the XML_CHAR_ENCODING_... values.

### xmlFindCharEncodingHandler ()

    xmlCharEncodingHandlerPtr	xmlFindCharEncodingHandler	(const char * name)

Search in the registered set the handler able to read/write that encoding.

`name`: | a string describing the char encoding.
`Returns`: | the handler or NULL if not found

### xmlGetCharEncodingHandler ()

    xmlCharEncodingHandlerPtr	xmlGetCharEncodingHandler	(xmlCharEncoding enc)

Search in the registered set the handler able to read/write that encoding.

`enc`: | an xmlCharEncoding value.
`Returns`: | the handler or NULL if not found

### xmlGetCharEncodingName ()

    const char *	xmlGetCharEncodingName	(xmlCharEncoding enc)

The "canonical" name for XML encoding. C.f. http://www.w3.org/TR/REC-xml#charencoding Section 4.3.3 Character Encoding in Entities

`enc`: | the encoding
`Returns`: | the canonical name for the given encoding

### xmlGetEncodingAlias ()

    const char *	xmlGetEncodingAlias	(const char * alias)

Lookup an encoding name for the given alias.

`alias`: | the alias name as parsed, in UTF-8 format (ASCII actually)
`Returns`: | NULL if not found, otherwise the original name

### xmlInitCharEncodingHandlers ()

    void	xmlInitCharEncodingHandlers	(void)

Initialize the char encoding support, it registers the default encoding supported. NOTE: while public, this function usually doesn't need to be called in normal processing.

### xmlNewCharEncodingHandler ()

    xmlCharEncodingHandlerPtr	xmlNewCharEncodingHandler	(const char * name,
    							 xmlCharEncodingInputFunc input,
    							 xmlCharEncodingOutputFunc output)

Create and registers an xmlCharEncodingHandler.

`name`: | the encoding name, in UTF-8 format (ASCII actually)
`input`: | the xmlCharEncodingInputFunc to read that encoding
`output`: | the xmlCharEncodingOutputFunc to write that encoding
`Returns`: | the xmlCharEncodingHandlerPtr created (or NULL in case of error).

### xmlParseCharEncoding ()

    xmlCharEncoding	xmlParseCharEncoding	(const char * name)

Compare the string to the encoding schemes already known. Note that the comparison is case insensitive accordingly to the section [XML] 4.3.3 Character Encoding in Entities.

`name`: | the encoding name as parsed, in UTF-8 format (ASCII actually)
`Returns`: | one of the XML_CHAR_ENCODING_... values or XML_CHAR_ENCODING_NONE if not recognized.

### xmlRegisterCharEncodingHandler ()

    void	xmlRegisterCharEncodingHandler	(xmlCharEncodingHandlerPtr handler)

Register the char encoding handler, surprising, isn't it ?

`handler`: | the xmlCharEncodingHandlerPtr handler block