Re: [xml] trying to build a document with a shared dictionary

[Martijn Faassen <faassen infrae com>]

Hey,

I'll take the opportunity to bring up this older issue again that I ran 
into. You suggested then to use shared dictionaries between documents to 
avoid a memory problem when moving nodes from one document to another.

Martijn Faassen wrote:

> One of the suggestions made to solve my node moves into other document 
> problem is to make sure all documents share their dictionaries. The 
> following code is my attempt, but valgrind is still not happy when 
> freeing the documents:
>
> #include "libxml/tree.h"
> #include "libxml/parser.h"
>
> /* parse document in context of document, sharing its dictionary */
> static xmlDocPtr xmlSharedDictReadDoc(const xmlDocPtr doc,
>                                       const xmlChar* text) {
>   xmlParserCtxtPtr pctxt;
>   xmlDocPtr ret;
>
>   xmlInitParser();
>
>   /* parse from text in memory */
>   pctxt = xmlCreateDocParserCtxt(text);
>
>   /* make sure dictionary is shared with doc's */
>   if ((doc != NULL) && (doc->dict != NULL) && (pctxt->dict != NULL)) {
>     xmlDictFree(pctxt->dict);
>     pctxt->dict = doc->dict;
>     xmlDictReference(pctxt->dict);
>   }
>
>   /* no net-loads, no entity expansion */
>   xmlCtxtUseOptions(pctxt, XML_PARSE_NONET | XML_PARSE_NOENT);
>
>   /* parse document */
>   xmlParseDocument(pctxt);
>
>   if (pctxt->wellFormed) {
>     ret = pctxt->myDoc;
>   }
>   else {
>     ret = NULL;
>     if (pctxt->myDoc != NULL)
>       xmlFreeDoc(pctxt->myDoc);
>     pctxt->myDoc = NULL;
>   }
>   xmlFreeParserCtxt(pctxt);
>
>   return(ret);
> }
>
> int main() {
>   xmlDoc* doc1;
>   xmlDoc* doc2;
>   xmlNode* node;
>   xmlChar* text = "<doc>foo</doc>";
>
>   /* parse the first document */
>   doc1 = xmlSharedDictReadDoc(NULL, text);
>   /* parse the second document, sharing dictionary of the first */
>   doc2 = xmlSharedDictReadDoc(doc1, text);
>
>   /* get the root node of the first document */
>   node = xmlDocGetRootElement(doc1);
>   /* set the root element in the other document */
>   xmlDocSetRootElement(doc2, node);
>   /* not sure whether xmlSetTreeDoc is necessary */
>   xmlSetTreeDoc(node, doc2);
>   /* reconciliate namespaces; shouldn't matter in this case */
>   xmlReconciliateNs(doc2, node);
>   /* now free both documents */
>   xmlFreeDoc(doc1);
>   xmlFreeDoc(doc2);
> }
>
> Any suggestions? I rather lost in the parser APIs, so I may very well be 
> doing something wrong.

Regards,

Martijn