[ expat-Bugs-580258 ] Problem with GetBuffer/ParseBuffer

Fri Jul 12 07:10:07 2002

Bugs item #580258, was opened at 2002-07-11 15:40
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Christopher M. Woods (cmwoods)
Assigned to: Nobody/Anonymous (nobody)
Summary: Problem with GetBuffer/ParseBuffer

Initial Comment:
This is my first post so forgive me if I leave anything 
out...
     I've encountered a problem while using the 
XML_GetBuffer/XML_ParserBuffer methods of the Expat 
library.  [Using libexpatw.lib, on Win2K w/ MSVC++ 6.0 -
 sp5, wide chars (UNICODE), with a UTF-16 encoded 
XML file of roughly 33KB of data.]  When using these 
methods, I've experienced errors from the parser stating 
one of the following: not well-formed XML, illegal token, 
or unclosed token.  Each of the errors appear 
consistently for a given file and a given buffer size.
     I haven't narrowed down the problem yet - and will 
include more information once I get a chance to dig into 
the code further.  I can tell you that I get no errors on the 
file if I read it into my own buffer and use the XML_Parse 
method.  I can also tell you that I DO GET errors if I 
request a buffer large enough for the file, read the file 
into the buffer, and then call XML_ParseBuffer... so the 
problem appears to be [at least on the surface] with 
XML_ParseBuffer.

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>Comment By: Karl Waclawek (kwaclaw)
Date: 2002-07-12 10:09

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I can't see your zip file.

Karl

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Comment By: Christopher M. Woods (cmwoods)
Date: 2002-07-12 09:41

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   Hmm... Perhaps I'm missing something in my setup or the 
delphi code isn't quite the same?  I'm using wchar_t 
(UNICODE & _UNICODE defines) and maybe the issue is 
related to that?  I've included a sample project in the zip file 
that exhibits the behaviorism that I'm seeing.
   The libexpatw.lib is right from the win32bin distribution 
(1.95.3) and the libexpatw_d.lib is a debug build I made from 
the included source code.
   If you look in XMLExtractor.cpp, in the Process() function, 
starting at line 52, you'll see both methodologies are coded 
and one is commented out.  The GetBuffer/ParseBuffer 
method fails for me and the Parse method (the 2nd one) 
seems to work fine.  [Separate question: Why does 
XML_Parse take const char* and not XML_Char*?]
   I'd be perfectly happy if this turns out to be nothing more 
that a simple configuration problem on my part.  But I'm 
curious why it seems to work fine one way and not the other.

Thank you for your time,
-Chris

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Comment By: Karl Waclawek (kwaclaw)
Date: 2002-07-11 21:22

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I cannot reproduce your problem with the current CVS
and also not with 1.95.3. I tested with the same buffer sizes 
you gave me.

I compiled the Dll with VC++6 (I believe I have SP5 also).
My test program is written in Delphi, but you can probably
still compare my parsing loop with yours:

const
  XML_READBUFSIZE = 65536;
...
IsFinal := False;
while not IsFinal do
  begin
  Buffer := XMLGetBuffer(Parser, XML_READBUFSIZE);
  if Buffer = nil then OutOfMemoryError;
  ReadCount := Stream.Read(Buffer^, XML_READBUFSIZE);
  IsFinal := ReadCount < XML_READBUFSIZE;
  if XMLParseBuffer(Parser, ReadCount, Integer(IsFinal)) = 0 
then
    begin
    ErrorCode := Ord(XMLGetErrorCode(Parser));
    ...
    Break;
    end;
  end;

Is that different?

Karl

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Comment By: Christopher M. Woods (cmwoods)
Date: 2002-07-11 17:51

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Frank,
   I was/am using the 1.95.3 version of the project.  I'll try the 
CVS version when I get a chance (very busy).

Karl,
   I've attached the sample file that I was using/having 
problems with.  I tried several buffer sizes including: 32768, 
65536, 1000000, and (if I remember correctly) 8192.

Thanks,
-Chris

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Comment By: Karl Waclawek (kwaclaw)
Date: 2002-07-11 16:01

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Would you mind attaching the file and giving me the 
buffer size you used?
I will try to duplicate the problem.

Karl

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Comment By: Fred L. Drake, Jr. (fdrake)
Date: 2002-07-11 15:51

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Are you using Expat 1.95.3 or the CVS version of Expat?

If you're not using the CVS version, can you take a look at
that version and try to reproduce the problem?  You can get
information on getting the CVS version anonymously at:

http://www.libexpat.org/dev/cvs.html

Thanks!

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https://sourceforge.net/tracker/?func=detail&atid=110127&aid=580258&group_id=10127