False document empty errors while doing SAX2 with ParseChunk

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)?

Thanx,
Joachim


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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
-- 
Red Hat Virtualization group http://redhat.com/v
irtualization/
Daniel Veillard      | virtualization library  http://libvirt.org/
veillardredhat.com  | libxml GNOME XML XSLT toolkit  http://xmlsoft.org/
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