Re: [xml] False document empty errors while doing SAX2 with ParseChunk

[Daniel Veillard <veillard redhat com>]

On Mon, Apr 02, 2007 at 07:41:07PM +0200, Joachim Zobel wrote:
> Hi.
> 
> I set up a parser context rather straightforward
> 
>     memset(&fctx->handler, 0, sizeof(xmlSAXHandler));
>     //xmlSAX2InitDefaultSAXHandler(&fctx->handler, 0);
>     /*
>      * Set handlers
>      */
> #define CALLBACK(fn,hdl) fctx->handler.fn = hdl
>     CALLBACK(startDocument, xml2_bucket_create_xml_decl);
>     CALLBACK(comment, xml2_bucket_create_comment);
>     CALLBACK(startElementNs, xml2_bucket_create_start);
>     CALLBACK(endElementNs, xml2_bucket_create_end);
>     CALLBACK(ignorableWhitespace, xml2_bucket_create_white);
>     CALLBACK(cdataBlock, xml2_bucket_create_cdata);
>     CALLBACK(characters, xml2_bucket_create_character);
>     CALLBACK(processingInstruction, xml2_bucket_create_proc_instr);
>     CALLBACK(warning, xml2_sax_warning);
>     CALLBACK(error, xml2_sax_error);
>     // mark as SAX2
>     fctx->handler.initialized = XML_SAX2_MAGIC;
> 
>     /* set up the parser */
>     fctx->sz_parsed = 0;
> 
>     xmlParserCtxt *parser = xmlCreatePushParserCtxt(&fctx->handler,
>                                                     fctx,NULL,0,NULL);
> 
> with fctx of type
> 
> typedef struct
> {
>     xmlParserCtxt parser;
> ....
> 
> When I then do 
> 
>     xmlParserErrors err = xmlParseChunk(&fctx->parser, buf, len, 0);
> 
> the first call succeeds and the sax events are generated.
> 
> The second call however gives me an error 4 - Document is empty. I know
> from the trace log this is not true.
> 
> Any hints what is going wrong (or shall I simply continue searching for
> memory corruption)?

  1/ do NOT use SAX unless you really know what you are doing and/or
     want to shave microseconds. Use the reader instead 
     http://xmlsoft.org/xmlreader.html
  2/ the code is incomplete, no way I can guess what's going on
     e.g. where is fctx->parser initialized ?
  3/ I suggest to follow the guidelines 
     http://xmlsoft.org/bugs.html
     try with xmllint --push on your document , verify it work, then
     base you code on xmllint.c section where --push is implemented.
     that should show how to use the push section, for the 
     SAX block initialization see the section for --sax option

Daniel
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