[xml] heap neutrality while outputting c14n

["Prashant R" <ramapra gmail com>]

Hello ,

I am trying to output c14n bytes of a specific node in my tree. 

For this purpose I have written a general purpose function that will generate C14n bytes by providing a xmlChar** ptr and the xmlNodePtr for which I need the c14n outpput . 

Issue : I would expect that after calling this function and after calling xmlFree() , heap consumption should return to the same value . 

I find that for a a node that contains  around 538 bytes I am losing around 2K bytes worth of heap memory 

eg Usage : 

OutsideFunction(xmlNodePtr pTopNode)

{

   ..

   xmlNodePtr pSubNode = < Some intermediate node unde pTopNode>

   xmlChar **c14data = NULL ; 

-----> Heap logging pt 1 

   if(ConvertXMLTreeToC14Bytes(pSubNode , c14data)>0)

 {

     // Do something 

    xmlFree(c14data);

------> Heap logging pt2 

 }

}

// generate c14n bytes

// output is ppBuffer 

/ user needs to call xmlFree after call to this function to free ppBuffer 

int ConvertXMLTreeToC14Bytes(xmlNodePtr pNode , xmlChar **ppBuffer )

{

if(pNode == NULL || ppBuffer == NULL)

return -1 ; 

int bytesWritten = 0; 

xmlDocPtr pDoc = NULL ; 

xmlDocPtr newDoc = NULL ; 

// if our parent is the doc node then this is top of tree 

if(pNode->doc->children == pNode)

{

pDoc = pNode->doc ; 

}

else

{

// This is a node other than the topmost node

// we create a new document with this node as the root

// create a new Doc 

newDoc = xmlNewDoc((const xmlChar *)"1.0");

if(newDoc == NULL)

return -1 ; 

// copy our node contents to a node under the new doc (newDoc)

// Create a copy of the node 

xmlNodePtr newNode = xmlDocCopyNodeList(newDoc , pNode ); 

if(newNode == NULL)

{

xmlFreeDoc(newDoc);

return -1; 

}

// Add a new node as top of tree for this new doc ! 

//xmlDocSetRootElement(newDoc , newNode);

pDoc = newDoc ; 

}

// now create canonical form 

// doc , All nodes ( NULL) , Exclusive canonicalization , no inclusive namespaces , NO comments in the result , ptr to client buffer ptr 

bytesWritten = xmlC14NDocDumpMemory(pDoc , NULL , 1, NULL, 0, ppBuffer);

if(newDoc)

{

xmlFreeDoc(newDoc) ; 

newDoc = NULL ; 

}

pDoc = NULL ;

return bytesWritten ;

}

Am I missing something here ? Any reason why I would be leaking some heap  ? 

Thanks