The following comment has been added to this issue:
Author: Dan Rosen
Created: Wed, 12 May 2004 2:38 PM
Body:
I have a fix that's just about ready. You can specify an optional maximum size for an
XMLBuffer and specify a handler to be invoked if the limit is reached. The handler
should make its best attempt to empty the buffer as appropriate to the task. In this
case, the handler for the fCDataBuf (a.k.a. "toUse" in XMLBuffer::scanCharData)
invokes XMLBuffer::sendCharData to send a characters() callback and flush the buffer.
This is the cleanest design I can think of: it requires no changes to any of the
scanning code in sendCharData or movePlainContentChars to handle the special case of
the buffer being full, and it should account for only minimal performance overhead in
XMLBuffer's internals (in most cases, only one if-zero comparison).
What I haven't gotten implemented yet is a way to pass a parameter at instantiation
time specifying this limit size. I'd like some feedback on how best to do this.
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View this comment:
http://issues.apache.org/jira/browse/XERCESC-1207?page=comments#action_35512
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View the issue:
http://issues.apache.org/jira/browse/XERCESC-1207
Here is an overview of the issue:
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Key: XERCESC-1207
Summary: XMLScanner::scanCharData fills XMLBuffer until out of memory
Type: Bug
Status: Unassigned
Priority: Critical
Project: Xerces-C++
Components:
Non-Validating Parser
Versions:
2.5.0
Assignee:
Reporter: Dan Rosen
Created: Mon, 10 May 2004 10:51 AM
Updated: Wed, 12 May 2004 2:38 PM
Description:
When parsing an XML file consisting primarily of very large (hundreds of megabytes)
blocks of contiguous character data, XMLScanner::scanCharData() happily attempts to
build a single XMLBuffer containing all the data. Eventually the buffer becomes so
large that the reallocation within XMLBuffer::insureCapacity() fails, causing
std::bad_alloc to be thrown, or a crash in memcpy (depending on compiler). The
fundamental problem seems to be that there is no upper bound imposed on buffer length.
In the SAX model, it is acceptable to issue multiple ContentHandler::characters()
callbacks for a single contiguous block of data. The only restriction on how this
should be implemented is that all characters in any single event must come from the
same external entity; no further behavior is specified. So it would be perfectly
conformant to the SAX model to set an upper bound on the size of a single characters()
event.
(As far as I understand, allowing an upper bound in XMLScanner::scanCharData() would
not affect the DOM)
I'd propose that an upper bound for character buffer size be added as an optional
parameter (with some reasonable value as a default), either in the constructor of the
parser or in useScanner(), and that that parameter be used to inform
XMLScanner::scanCharData() when to force a call to sendCharData() to dump the buffer
to its client.
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