DO NOT REPLY [Bug 10593] New: - Recursion limits, excessive memory consumption [patch attached]

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http://nagoya.apache.org/bugzilla/show_bug.cgi?id=10593

Recursion limits, excessive memory consumption [patch attached]

           Summary: Recursion limits, excessive memory consumption [patch
                    attached]
           Product: XalanJ2
           Version: 2.4Dx
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: Other
         Component: org.apache.xpath
        AssignedTo: xalan-dev@xml.apache.org
        ReportedBy: nboyd@atg.com


org.apache.xpath.XPathContext defines a constant RECURSIONLIMIT and several 
arrays that are allocated with that length and whose bounds are never checked.
This causes two problems: the potential for ArrayIndexOutOfBoundsExceptions and 
excessive memory consumption by programs that make repeated use of XPath 
expressions.

We had a customer who was using XPath to select nodes to compose a page to 
display on the web and was generating on the order of 160Mb of garbage *per 
request*. 

The attached patch removes RECURSIONLIMIT and replaces it with an initial stack
size. When elements are pushed onto the arrays, the size of the array is checked
and the array is grown if need be. I removed two getter methods for retrieving
the array since that array may be replaced by a larger array without notification
of the caller. 

In our tests, these changes improved performance by reducing the pressure on the
garbage collector. Our tests didn't see any array growth for the proposed
initial stack size value.

To test the changes, I set the initial size of the arrays to 2 and ran several
of the samples through, including ApplyXPath. At this artificially low level,
I saw several arrays grow.