Module xmlIO from libxml2

# ## Module xmlIO from libxml2

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interface for the I/O interfaces used by the parser ## Table of Contents
    xmlOutputBufferPtr	xmlAllocOutputBuffer	(xmlCharEncodingHandlerPtr encoder)
    xmlParserInputBufferPtr	xmlAllocParserInputBuffer	(xmlCharEncoding enc)
    int	xmlCheckFilename		(const char * path)
    xmlParserInputPtr	xmlCheckHTTPInput	(xmlParserCtxtPtr ctxt,
    						 xmlParserInputPtr ret)
    void	xmlCleanupInputCallbacks	(void)
    void	xmlCleanupOutputCallbacks	(void)
    int	xmlFileClose			(void * context)
    int	xmlFileMatch			(const char * filename)
    void *	xmlFileOpen			(const char * filename)
    int	xmlFileRead			(void * context,
    					 char * buffer,
    					 int len)
    void	xmlFreeParserInputBuffer	(xmlParserInputBufferPtr in)
    int	xmlIOFTPClose			(void * context)
    int	xmlIOFTPMatch			(const char * filename)
    void *	xmlIOFTPOpen			(const char * filename)
    int	xmlIOFTPRead			(void * context,
    					 char * buffer,
    					 int len)
    int	xmlIOHTTPClose			(void * context)
    int	xmlIOHTTPMatch			(const char * filename)
    void *	xmlIOHTTPOpen			(const char * filename)
    void *	xmlIOHTTPOpenW			(const char * post_uri,
    					 int compression)
    int	xmlIOHTTPRead			(void * context,
    					 char * buffer,
    					 int len)
    Function type: xmlInputCloseCallback
    int	xmlInputCloseCallback		(void * context)
    Function type: xmlInputMatchCallback
    int	xmlInputMatchCallback		(char const * filename)
    Function type: xmlInputOpenCallback
    void *	xmlInputOpenCallback		(char const * filename)
    Function type: xmlInputReadCallback
    int	xmlInputReadCallback		(void * context,
    					 char * buffer,
    					 int len)
    xmlParserInputPtr	xmlNoNetExternalEntityLoader	(const char * URL,
    							 const char * ID,
    							 xmlParserCtxtPtr ctxt)
    xmlChar *	xmlNormalizeWindowsPath	(const xmlChar * path)
    int	xmlOutputBufferClose		(xmlOutputBufferPtr out)
    xmlOutputBufferPtr	xmlOutputBufferCreateBuffer	(xmlBufferPtr buffer,
    							 xmlCharEncodingHandlerPtr encoder)
    xmlOutputBufferPtr	xmlOutputBufferCreateFd	(int fd,
    						 xmlCharEncodingHandlerPtr encoder)
    xmlOutputBufferPtr	xmlOutputBufferCreateFile	(FILE * file,
    							 xmlCharEncodingHandlerPtr encoder)
    xmlOutputBufferPtr	xmlOutputBufferCreateFilename	(const char * URI,
    							 xmlCharEncodingHandlerPtr encoder,
    							 int compression)
    xmlOutputBufferPtr	xmlOutputBufferCreateIO	(xmlOutputWriteCallback iowrite,
    						 xmlOutputCloseCallback ioclose,
    						 void * ioctx,
    						 xmlCharEncodingHandlerPtr encoder)
    int	xmlOutputBufferFlush		(xmlOutputBufferPtr out)
    int	xmlOutputBufferWrite		(xmlOutputBufferPtr out,
    					 int len,
    					 const char * buf)
    int	xmlOutputBufferWriteEscape	(xmlOutputBufferPtr out,
    					 const xmlChar * str,
    					 xmlCharEncodingOutputFunc escaping)
    int	xmlOutputBufferWriteString	(xmlOutputBufferPtr out,
    					 const char * str)
    Function type: xmlOutputCloseCallback
    int	xmlOutputCloseCallback		(void * context)
    Function type: xmlOutputMatchCallback
    int	xmlOutputMatchCallback		(char const * filename)
    Function type: xmlOutputOpenCallback
    void *	xmlOutputOpenCallback		(char const * filename)
    Function type: xmlOutputWriteCallback
    int	xmlOutputWriteCallback		(void * context,
    					 const char * buffer,
    					 int len)
    char *	xmlParserGetDirectory		(const char * filename)
    xmlParserInputBufferPtr	xmlParserInputBufferCreateFd	(int fd,
    							 xmlCharEncoding enc)
    xmlParserInputBufferPtr	xmlParserInputBufferCreateFile	(FILE * file,
    							 xmlCharEncoding enc)
    xmlParserInputBufferPtr	xmlParserInputBufferCreateFilename	(const char * URI,
    							 xmlCharEncoding enc)
    xmlParserInputBufferPtr	xmlParserInputBufferCreateIO	(xmlInputReadCallback ioread,
    							 xmlInputCloseCallback ioclose,
    							 void * ioctx,
    							 xmlCharEncoding enc)
    xmlParserInputBufferPtr	xmlParserInputBufferCreateMem	(const char * mem,
    							 int size,
    							 xmlCharEncoding enc)
    xmlParserInputBufferPtr	xmlParserInputBufferCreateStatic	(const char * mem,
    							 int size,
    							 xmlCharEncoding enc)
    int	xmlParserInputBufferGrow	(xmlParserInputBufferPtr in,
    					 int len)
    int	xmlParserInputBufferPush	(xmlParserInputBufferPtr in,
    					 int len,
    					 const char * buf)
    int	xmlParserInputBufferRead	(xmlParserInputBufferPtr in,
    					 int len)
    int	xmlPopInputCallbacks		(void)
    void	xmlRegisterDefaultInputCallbacks	(void)
    void	xmlRegisterDefaultOutputCallbacks	(void)
    void	xmlRegisterHTTPPostCallbacks	(void)
    int	xmlRegisterInputCallbacks	(xmlInputMatchCallback matchFunc,
    					 xmlInputOpenCallback openFunc,
    					 xmlInputReadCallback readFunc,
    					 xmlInputCloseCallback closeFunc)
    int	xmlRegisterOutputCallbacks	(xmlOutputMatchCallback matchFunc,
    					 xmlOutputOpenCallback openFunc,
    					 xmlOutputWriteCallback writeFunc,
    					 xmlOutputCloseCallback closeFunc)
## Description ### Function: xmlAllocOutputBuffer
    xmlOutputBufferPtr	xmlAllocOutputBuffer	(xmlCharEncodingHandlerPtr encoder)
Create a buffered parser output
`encoder`: | the encoding converter or NULL
`Returns`: | the new parser output or NULL
### Function: xmlAllocParserInputBuffer
    xmlParserInputBufferPtr	xmlAllocParserInputBuffer	(xmlCharEncoding enc)
Create a buffered parser input for progressive parsing
`enc`: | the charset encoding if known
`Returns`: | the new parser input or NULL
### Function: xmlCheckFilename
    int	xmlCheckFilename		(const char * path)
function checks to see if @path is a valid source (file, socket...) for XML. if stat is not available on the target machine,
`path`: | the path to check
`Returns`: | 1. if stat fails, returns 0 (if calling stat on the filename fails, it can't be right). if stat succeeds and the file is a directory, returns 2. otherwise returns 1.
### Function: xmlCheckHTTPInput
    xmlParserInputPtr	xmlCheckHTTPInput	(xmlParserCtxtPtr ctxt,
    						 xmlParserInputPtr ret)
Check an input in case it was created from an HTTP stream, in that case it will handle encoding and update of the base URL in case of redirection. It also checks for HTTP errors in which case the input is cleanly freed up and an appropriate error is raised in context
`ctxt`: | an XML parser context
`ret`: | an XML parser input
`Returns`: | the input or NULL in case of HTTP error.
### Function: xmlCleanupInputCallbacks
    void	xmlCleanupInputCallbacks	(void)
clears the entire input callback table. this includes the compiled-in I/O. ### Function: xmlCleanupOutputCallbacks
    void	xmlCleanupOutputCallbacks	(void)
clears the entire output callback table. this includes the compiled-in I/O callbacks. ### Function: xmlFileClose
    int	xmlFileClose			(void * context)
Close an I/O channel
`context`: | the I/O context
`Returns`: | 0 or -1 in case of error
### Function: xmlFileMatch
    int	xmlFileMatch			(const char * filename)
input from FILE *
`filename`: | the URI for matching
`Returns`: | 1 if matches, 0 otherwise
### Function: xmlFileOpen
    void *	xmlFileOpen			(const char * filename)
Wrapper around xmlFileOpen_real that try it with an unescaped version of @filename, if this fails fallback to @filename
`filename`: | the URI for matching
`Returns`: | a handler or NULL in case or failure
### Function: xmlFileRead
    int	xmlFileRead			(void * context,
    					 char * buffer,
    					 int len)
Read @len bytes to @buffer from the I/O channel.
`context`: | the I/O context
`buffer`: | where to drop data
`len`: | number of bytes to write
`Returns`: | the number of bytes written or < 0 in case of failure
### Function: xmlFreeParserInputBuffer
    void	xmlFreeParserInputBuffer	(xmlParserInputBufferPtr in)
Free up the memory used by a buffered parser input
`in`: | a buffered parser input
### Function: xmlIOFTPClose
    int	xmlIOFTPClose			(void * context)
Close an FTP I/O channel
`context`: | the I/O context
`Returns`: | 0
### Function: xmlIOFTPMatch
    int	xmlIOFTPMatch			(const char * filename)
check if the URI matches an FTP one
`filename`: | the URI for matching
`Returns`: | 1 if matches, 0 otherwise
### Function: xmlIOFTPOpen
    void *	xmlIOFTPOpen			(const char * filename)
open an FTP I/O channel
`filename`: | the URI for matching
`Returns`: | an I/O context or NULL in case of error
### Function: xmlIOFTPRead
    int	xmlIOFTPRead			(void * context,
    					 char * buffer,
    					 int len)
Read @len bytes to @buffer from the I/O channel.
`context`: | the I/O context
`buffer`: | where to drop data
`len`: | number of bytes to write
`Returns`: | the number of bytes written
### Function: xmlIOHTTPClose
    int	xmlIOHTTPClose			(void * context)
Close an HTTP I/O channel
`context`: | the I/O context
`Returns`: | 0
### Function: xmlIOHTTPMatch
    int	xmlIOHTTPMatch			(const char * filename)
check if the URI matches an HTTP one
`filename`: | the URI for matching
`Returns`: | 1 if matches, 0 otherwise
### Function: xmlIOHTTPOpen
    void *	xmlIOHTTPOpen			(const char * filename)
open an HTTP I/O channel
`filename`: | the URI for matching
`Returns`: | an I/O context or NULL in case of error
### Function: xmlIOHTTPOpenW
    void *	xmlIOHTTPOpenW			(const char * post_uri,
    					 int compression)
Open a temporary buffer to collect the document for a subsequent HTTP POST request. Non-static as is called from the output buffer creation routine.
`post_uri`: | The destination URI for the document
`compression`: | The compression desired for the document.
`Returns`: | an I/O context or NULL in case of error.
### Function: xmlIOHTTPRead
    int	xmlIOHTTPRead			(void * context,
    					 char * buffer,
    					 int len)
Read @len bytes to @buffer from the I/O channel.
`context`: | the I/O context
`buffer`: | where to drop data
`len`: | number of bytes to write
`Returns`: | the number of bytes written
### Function type: xmlInputCloseCallback
    Function type: xmlInputCloseCallback
    int	xmlInputCloseCallback		(void * context)
Callback used in the I/O Input API to close the resource
`context`: | an Input context
`Returns`: | 0 or -1 in case of error
### Function type: xmlInputMatchCallback
    Function type: xmlInputMatchCallback
    int	xmlInputMatchCallback		(char const * filename)
Callback used in the I/O Input API to detect if the current handler can provide input fonctionnalities for this resource.
`filename`: | the filename or URI
`Returns`: | 1 if yes and 0 if another Input module should be used
### Function type: xmlInputOpenCallback
    Function type: xmlInputOpenCallback
    void *	xmlInputOpenCallback		(char const * filename)
Callback used in the I/O Input API to open the resource
`filename`: | the filename or URI
`Returns`: | an Input context or NULL in case or error
### Function type: xmlInputReadCallback
    Function type: xmlInputReadCallback
    int	xmlInputReadCallback		(void * context,
    					 char * buffer,
    					 int len)
Callback used in the I/O Input API to read the resource
`context`: | an Input context
`buffer`: | the buffer to store data read
`len`: | the length of the buffer in bytes
`Returns`: | the number of bytes read or -1 in case of error
### Function: xmlNoNetExternalEntityLoader
    xmlParserInputPtr	xmlNoNetExternalEntityLoader	(const char * URL,
    							 const char * ID,
    							 xmlParserCtxtPtr ctxt)
A specific entity loader disabling network accesses, though still allowing local catalog accesses for resolution.
`URL`: | the URL for the entity to load
`ID`: | the System ID for the entity to load
`ctxt`: | the context in which the entity is called or NULL
`Returns`: | a new allocated xmlParserInputPtr, or NULL.
### Function: xmlNormalizeWindowsPath
    xmlChar *	xmlNormalizeWindowsPath	(const xmlChar * path)
This function is obsolete. Please see xmlURIFromPath in uri.c for a better solution.
`path`: | the input file path
`Returns`: | a canonicalized version of the path
### Function: xmlOutputBufferClose
    int	xmlOutputBufferClose		(xmlOutputBufferPtr out)
flushes and close the output I/O channel and free up all the associated resources
`out`: | a buffered output
`Returns`: | the number of byte written or -1 in case of error.
### Function: xmlOutputBufferCreateBuffer
    xmlOutputBufferPtr	xmlOutputBufferCreateBuffer	(xmlBufferPtr buffer,
    							 xmlCharEncodingHandlerPtr encoder)
Create a buffered output for the progressive saving to a xmlBuffer
`buffer`: | a xmlBufferPtr
`encoder`: | the encoding converter or NULL
`Returns`: | the new parser output or NULL
### Function: xmlOutputBufferCreateFd
    xmlOutputBufferPtr	xmlOutputBufferCreateFd	(int fd,
    						 xmlCharEncodingHandlerPtr encoder)
Create a buffered output for the progressive saving to a file descriptor
`fd`: | a file descriptor number
`encoder`: | the encoding converter or NULL
`Returns`: | the new parser output or NULL
### Function: xmlOutputBufferCreateFile
    xmlOutputBufferPtr	xmlOutputBufferCreateFile	(FILE * file,
    							 xmlCharEncodingHandlerPtr encoder)
Create a buffered output for the progressive saving to a FILE * buffered C I/O
`file`: | a FILE*
`encoder`: | the encoding converter or NULL
`Returns`: | the new parser output or NULL
### Function: xmlOutputBufferCreateFilename
    xmlOutputBufferPtr	xmlOutputBufferCreateFilename	(const char * URI,
    							 xmlCharEncodingHandlerPtr encoder,
    							 int compression)
Create a buffered output for the progressive saving of a file If filename is "-' then we use stdout as the output. Automatic support for ZLIB/Compress compressed document is provided by default if found at compile-time. TODO: currently if compression is set, the library only support writing to a local file.
`URI`: | a C string containing the URI or filename
`encoder`: | the encoding converter or NULL
`compression`: | the compression ration (0 none, 9 max).
`Returns`: | the new output or NULL
### Function: xmlOutputBufferCreateIO
    xmlOutputBufferPtr	xmlOutputBufferCreateIO	(xmlOutputWriteCallback iowrite,
    						 xmlOutputCloseCallback ioclose,
    						 void * ioctx,
    						 xmlCharEncodingHandlerPtr encoder)
Create a buffered output for the progressive saving to an I/O handler
`iowrite`: | an I/O write function
`ioclose`: | an I/O close function
`ioctx`: | an I/O handler
`encoder`: | the charset encoding if known
`Returns`: | the new parser output or NULL
### Function: xmlOutputBufferFlush
    int	xmlOutputBufferFlush		(xmlOutputBufferPtr out)
flushes the output I/O channel
`out`: | a buffered output
`Returns`: | the number of byte written or -1 in case of error.
### Function: xmlOutputBufferWrite
    int	xmlOutputBufferWrite		(xmlOutputBufferPtr out,
    					 int len,
    					 const char * buf)
Write the content of the array in the output I/O buffer This routine handle the I18N transcoding from internal UTF-8 The buffer is lossless, i.e. will store in case of partial or delayed writes.
`out`: | a buffered parser output
`len`: | the size in bytes of the array.
`buf`: | an char array
`Returns`: | the number of chars immediately written, or -1 in case of error.
### Function: xmlOutputBufferWriteEscape
    int	xmlOutputBufferWriteEscape	(xmlOutputBufferPtr out,
    					 const xmlChar * str,
    					 xmlCharEncodingOutputFunc escaping)
Write the content of the string in the output I/O buffer This routine escapes the caracters and then handle the I18N transcoding from internal UTF-8 The buffer is lossless, i.e. will store in case of partial or delayed writes.
`out`: | a buffered parser output
`str`: | a zero terminated UTF-8 string
`escaping`: | an optional escaping function (or NULL)
`Returns`: | the number of chars immediately written, or -1 in case of error.
### Function: xmlOutputBufferWriteString
    int	xmlOutputBufferWriteString	(xmlOutputBufferPtr out,
    					 const char * str)
Write the content of the string in the output I/O buffer This routine handle the I18N transcoding from internal UTF-8 The buffer is lossless, i.e. will store in case of partial or delayed writes.
`out`: | a buffered parser output
`str`: | a zero terminated C string
`Returns`: | the number of chars immediately written, or -1 in case of error.
### Function type: xmlOutputCloseCallback
    Function type: xmlOutputCloseCallback
    int	xmlOutputCloseCallback		(void * context)
Callback used in the I/O Output API to close the resource
`context`: | an Output context
`Returns`: | 0 or -1 in case of error
### Function type: xmlOutputMatchCallback
    Function type: xmlOutputMatchCallback
    int	xmlOutputMatchCallback		(char const * filename)
Callback used in the I/O Output API to detect if the current handler can provide output fonctionnalities for this resource.
`filename`: | the filename or URI
`Returns`: | 1 if yes and 0 if another Output module should be used
### Function type: xmlOutputOpenCallback
    Function type: xmlOutputOpenCallback
    void *	xmlOutputOpenCallback		(char const * filename)
Callback used in the I/O Output API to open the resource
`filename`: | the filename or URI
`Returns`: | an Output context or NULL in case or error
### Function type: xmlOutputWriteCallback
    Function type: xmlOutputWriteCallback
    int	xmlOutputWriteCallback		(void * context,
    					 const char * buffer,
    					 int len)
Callback used in the I/O Output API to write to the resource
`context`: | an Output context
`buffer`: | the buffer of data to write
`len`: | the length of the buffer in bytes
`Returns`: | the number of bytes written or -1 in case of error
### Function: xmlParserGetDirectory
    char *	xmlParserGetDirectory		(const char * filename)
lookup the directory for that file
`filename`: | the path to a file
`Returns`: | a new allocated string containing the directory, or NULL.
### Function: xmlParserInputBufferCreateFd
    xmlParserInputBufferPtr	xmlParserInputBufferCreateFd	(int fd,
    							 xmlCharEncoding enc)
Create a buffered parser input for the progressive parsing for the input from a file descriptor
`fd`: | a file descriptor number
`enc`: | the charset encoding if known
`Returns`: | the new parser input or NULL
### Function: xmlParserInputBufferCreateFile
    xmlParserInputBufferPtr	xmlParserInputBufferCreateFile	(FILE * file,
    							 xmlCharEncoding enc)
Create a buffered parser input for the progressive parsing of a FILE * buffered C I/O
`file`: | a FILE*
`enc`: | the charset encoding if known
`Returns`: | the new parser input or NULL
### Function: xmlParserInputBufferCreateFilename
    xmlParserInputBufferPtr	xmlParserInputBufferCreateFilename	(const char * URI,
    							 xmlCharEncoding enc)
Create a buffered parser input for the progressive parsing of a file If filename is "-' then we use stdin as the input. Automatic support for ZLIB/Compress compressed document is provided by default if found at compile-time. Do an encoding check if enc == XML_CHAR_ENCODING_NONE
`URI`: | a C string containing the URI or filename
`enc`: | the charset encoding if known
`Returns`: | the new parser input or NULL
### Function: xmlParserInputBufferCreateIO
    xmlParserInputBufferPtr	xmlParserInputBufferCreateIO	(xmlInputReadCallback ioread,
    							 xmlInputCloseCallback ioclose,
    							 void * ioctx,
    							 xmlCharEncoding enc)
Create a buffered parser input for the progressive parsing for the input from an I/O handler
`ioread`: | an I/O read function
`ioclose`: | an I/O close function
`ioctx`: | an I/O handler
`enc`: | the charset encoding if known
`Returns`: | the new parser input or NULL
### Function: xmlParserInputBufferCreateMem
    xmlParserInputBufferPtr	xmlParserInputBufferCreateMem	(const char * mem,
    							 int size,
    							 xmlCharEncoding enc)
Create a buffered parser input for the progressive parsing for the input from a memory area.
`mem`: | the memory input
`size`: | the length of the memory block
`enc`: | the charset encoding if known
`Returns`: | the new parser input or NULL
### Function: xmlParserInputBufferCreateStatic
    xmlParserInputBufferPtr	xmlParserInputBufferCreateStatic	(const char * mem,
    							 int size,
    							 xmlCharEncoding enc)
Create a buffered parser input for the progressive parsing for the input from an immutable memory area. This will not copy the memory area to the buffer, but the memory is expected to be available until the end of the parsing, this is useful for example when using mmap'ed file.
`mem`: | the memory input
`size`: | the length of the memory block
`enc`: | the charset encoding if known
`Returns`: | the new parser input or NULL
### Function: xmlParserInputBufferGrow
    int	xmlParserInputBufferGrow	(xmlParserInputBufferPtr in,
    					 int len)
Grow up the content of the input buffer, the old data are preserved This routine handle the I18N transcoding to internal UTF-8 This routine is used when operating the parser in normal (pull) mode TODO: one should be able to remove one extra copy by copying directly onto in->buffer or in->raw
`in`: | a buffered parser input
`len`: | indicative value of the amount of chars to read
`Returns`: | the number of chars read and stored in the buffer, or -1 in case of error.
### Function: xmlParserInputBufferPush
    int	xmlParserInputBufferPush	(xmlParserInputBufferPtr in,
    					 int len,
    					 const char * buf)
Push the content of the arry in the input buffer This routine handle the I18N transcoding to internal UTF-8 This is used when operating the parser in progressive (push) mode.
`in`: | a buffered parser input
`len`: | the size in bytes of the array.
`buf`: | an char array
`Returns`: | the number of chars read and stored in the buffer, or -1 in case of error.
### Function: xmlParserInputBufferRead
    int	xmlParserInputBufferRead	(xmlParserInputBufferPtr in,
    					 int len)
Refresh the content of the input buffer, the old data are considered consumed This routine handle the I18N transcoding to internal UTF-8
`in`: | a buffered parser input
`len`: | indicative value of the amount of chars to read
`Returns`: | the number of chars read and stored in the buffer, or -1 in case of error.
### Function: xmlPopInputCallbacks
    int	xmlPopInputCallbacks		(void)
Clear the top input callback from the input stack. this includes the compiled-in I/O.
`Returns`: | the number of input callback registered or -1 in case of error.
### Function: xmlRegisterDefaultInputCallbacks
    void	xmlRegisterDefaultInputCallbacks	(void)
Registers the default compiled-in I/O handlers. ### Function: xmlRegisterDefaultOutputCallbacks
    void	xmlRegisterDefaultOutputCallbacks	(void)
Registers the default compiled-in I/O handlers. ### Function: xmlRegisterHTTPPostCallbacks
    void	xmlRegisterHTTPPostCallbacks	(void)
By default, libxml submits HTTP output requests using the "PUT" method. Calling this method changes the HTTP output method to use the "POST" method instead. ### Function: xmlRegisterInputCallbacks
    int	xmlRegisterInputCallbacks	(xmlInputMatchCallback matchFunc,
    					 xmlInputOpenCallback openFunc,
    					 xmlInputReadCallback readFunc,
    					 xmlInputCloseCallback closeFunc)
Register a new set of I/O callback for handling parser input.
`matchFunc`: | the xmlInputMatchCallback
`openFunc`: | the xmlInputOpenCallback
`readFunc`: | the xmlInputReadCallback
`closeFunc`: | the xmlInputCloseCallback
`Returns`: | the registered handler number or -1 in case of error
### Function: xmlRegisterOutputCallbacks
    int	xmlRegisterOutputCallbacks	(xmlOutputMatchCallback matchFunc,
    					 xmlOutputOpenCallback openFunc,
    					 xmlOutputWriteCallback writeFunc,
    					 xmlOutputCloseCallback closeFunc)
Register a new set of I/O callback for handling output.
`matchFunc`: | the xmlOutputMatchCallback
`openFunc`: | the xmlOutputOpenCallback
`writeFunc`: | the xmlOutputWriteCallback
`closeFunc`: | the xmlOutputCloseCallback
`Returns`: | the registered handler number or -1 in case of error
Daniel Veillard