c14n: Provide Canonical XML and Exclusive XML Canonicalization

## c14n

c14n - Provide Canonical XML and Exclusive XML Canonicalization

the c14n modules provides a "Canonical XML" implementation

Author(s): Aleksey Sanin <aleksey@aleksey.com>

## Synopsis

    typedef enum xmlC14NMode;
    int	xmlC14NExecute			(xmlDocPtr doc,
    					 xmlC14NIsVisibleCallback is_visible_callback,
    					 void * user_data,
    					 int mode,
    					 xmlChar ** inclusive_ns_prefixes,
    					 int with_comments,
    					 xmlOutputBufferPtr buf);
    int	xmlC14NDocSaveTo		(xmlDocPtr doc,
    					 xmlNodeSetPtr nodes,
    					 int mode,
    					 xmlChar ** inclusive_ns_prefixes,
    					 int with_comments,
    					 xmlOutputBufferPtr buf);
    typedef int xmlC14NIsVisibleCallback	(void * user_data,
    					 xmlNodePtr node,
    					 xmlNodePtr parent);
    int	xmlC14NDocSave			(xmlDocPtr doc,
    					 xmlNodeSetPtr nodes,
    					 int mode,
    					 xmlChar ** inclusive_ns_prefixes,
    					 int with_comments,
    					 const char * filename,
    					 int compression);
    int	xmlC14NDocDumpMemory		(xmlDocPtr doc,
    					 xmlNodeSetPtr nodes,
    					 int mode,
    					 xmlChar ** inclusive_ns_prefixes,
    					 int with_comments,
    					 xmlChar ** doc_txt_ptr);

## Description

## Details

### Enum xmlC14NMode

    enum xmlC14NMode {
        XML_C14N_1_0 = 0 /* Original C14N 1.0 spec */
        XML_C14N_EXCLUSIVE_1_0 = 1 /* Exclusive C14N 1.0 spec */
        XML_C14N_1_1 = 2 /*  C14N 1.1 spec */
    };

### Function type xmlC14NIsVisibleCallback

    int	xmlC14NIsVisibleCallback	(void * user_data,
    					 xmlNodePtr node,
    					 xmlNodePtr parent)

Signature for a C14N callback on visible nodes

`user_data`: | user data
`node`: | the current node
`parent`: | the parent node
`Returns`: | 1 if the node should be included

### xmlC14NDocDumpMemory ()

    int	xmlC14NDocDumpMemory		(xmlDocPtr doc,
    					 xmlNodeSetPtr nodes,
    					 int mode,
    					 xmlChar ** inclusive_ns_prefixes,
    					 int with_comments,
    					 xmlChar ** doc_txt_ptr)

Dumps the canonized image of given XML document into memory. For details see "Canonical XML" (http://www.w3.org/TR/xml-c14n) or "Exclusive XML Canonicalization" (http://www.w3.org/TR/xml-exc-c14n)

`doc`: | the XML document for canonization
`nodes`: | the nodes set to be included in the canonized image or NULL if all document nodes should be included
`mode`: | the c14n mode (see @xmlC14NMode)
`inclusive_ns_prefixes`: | the list of inclusive namespace prefixes ended with a NULL or NULL if there is no inclusive namespaces (only for exclusive canonicalization, ignored otherwise)
`with_comments`: | include comments in the result (!=0) or not (==0)
`doc_txt_ptr`: | the memory pointer for allocated canonical XML text; the caller of this functions is responsible for calling xmlFree() to free allocated memory
`Returns`: | the number of bytes written on success or a negative value on fail

### xmlC14NDocSave ()

    int	xmlC14NDocSave			(xmlDocPtr doc,
    					 xmlNodeSetPtr nodes,
    					 int mode,
    					 xmlChar ** inclusive_ns_prefixes,
    					 int with_comments,
    					 const char * filename,
    					 int compression)

Dumps the canonized image of given XML document into the file. For details see "Canonical XML" (http://www.w3.org/TR/xml-c14n) or "Exclusive XML Canonicalization" (http://www.w3.org/TR/xml-exc-c14n)

`doc`: | the XML document for canonization
`nodes`: | the nodes set to be included in the canonized image or NULL if all document nodes should be included
`mode`: | the c14n mode (see @xmlC14NMode)
`inclusive_ns_prefixes`: | the list of inclusive namespace prefixes ended with a NULL or NULL if there is no inclusive namespaces (only for exclusive canonicalization, ignored otherwise)
`with_comments`: | include comments in the result (!=0) or not (==0)
`filename`: | the filename to store canonical XML image
`compression`: | the compression level (zlib required): -1 - libxml default, 0 - uncompressed, >0 - compression level
`Returns`: | the number of bytes written success or a negative value on fail

### xmlC14NDocSaveTo ()

    int	xmlC14NDocSaveTo		(xmlDocPtr doc,
    					 xmlNodeSetPtr nodes,
    					 int mode,
    					 xmlChar ** inclusive_ns_prefixes,
    					 int with_comments,
    					 xmlOutputBufferPtr buf)

Dumps the canonized image of given XML document into the provided buffer. For details see "Canonical XML" (http://www.w3.org/TR/xml-c14n) or "Exclusive XML Canonicalization" (http://www.w3.org/TR/xml-exc-c14n)

`doc`: | the XML document for canonization
`nodes`: | the nodes set to be included in the canonized image or NULL if all document nodes should be included
`mode`: | the c14n mode (see @xmlC14NMode)
`inclusive_ns_prefixes`: | the list of inclusive namespace prefixes ended with a NULL or NULL if there is no inclusive namespaces (only for exclusive canonicalization, ignored otherwise)
`with_comments`: | include comments in the result (!=0) or not (==0)
`buf`: | the output buffer to store canonical XML; this buffer MUST have encoder==NULL because C14N requires UTF-8 output
`Returns`: | non-negative value on success or a negative value on fail

### xmlC14NExecute ()

    int	xmlC14NExecute			(xmlDocPtr doc,
    					 xmlC14NIsVisibleCallback is_visible_callback,
    					 void * user_data,
    					 int mode,
    					 xmlChar ** inclusive_ns_prefixes,
    					 int with_comments,
    					 xmlOutputBufferPtr buf)

Dumps the canonized image of given XML document into the provided buffer. For details see "Canonical XML" (http://www.w3.org/TR/xml-c14n) or "Exclusive XML Canonicalization" (http://www.w3.org/TR/xml-exc-c14n)

`doc`: | the XML document for canonization
`is_visible_callback`: | the function to use to determine is node visible or not
`user_data`: | the first parameter for @is_visible_callback function (in most cases, it is nodes set)
`mode`: | the c14n mode (see @xmlC14NMode)
`inclusive_ns_prefixes`: | the list of inclusive namespace prefixes ended with a NULL or NULL if there is no inclusive namespaces (only for exclusive canonicalization, ignored otherwise)
`with_comments`: | include comments in the result (!=0) or not (==0)
`buf`: | the output buffer to store canonical XML; this buffer MUST have encoder==NULL because C14N requires UTF-8 output
`Returns`: | non-negative value on success or a negative value on fail