XOM API for Processing XML with Java

["Michael Kay" <mike AT saxonica.com>]

Another case to consider is where the events are coming from the output of
an XSLT transformation, where it's quite likely that each <xsl:value-of>
instruction or piece of literal text in the stylesheet will lead to a call
on characters().

Michael Kay
http://www.saxonica.com/  

> -----Original Message-----
> From: xom-interest-bounces AT lists.ibiblio.org 
> [mailto:xom-interest-bounces AT lists.ibiblio.org] On Behalf Of 
> Elliotte Harold
> Sent: 22 July 2005 12:33
> To: Wolfgang Hoschek
> Cc: xom-interest AT lists.ibiblio.org
> Subject: Re: [XOM-interest] More parsing performance patches
> 
> The second new optimization I see here is avoiding the creation of 
> intermediate string buffers for most calls to characters. Your 
> measurements match my expectations that most of the time there'll be 
> exactly one call to characters() per call to flushText(). The 
> exceptions 
> tend to occur on a  few corners:
> 
> 1. Documents with very large (16K+) runs of plain, unmarked up text
> 2. A few parsers that call characters separately for entity and/or 
> character references
> 3. One particularly brain-damaged older version of Xerces 
> that actually 
> invoked the characters() method once for each and every character in 
> plain text that was loaded from entity references
> 4. A few parsers may call characters separately when a CDATA section 
> interrupts non-CDATA section text
> 
> Only #1 is really worth considering when optimizing, and even that's 
> uncommon.
> 
> The basic idea looks good. Given that more than one call to 
> characters 
> per text, I wonder if we can simplify it somewhat. Suppose we ignored 
> StringBuffers completely? In other words, if characters was called a 
> second or third time we just append directly to the string? 
> This would 
> leave the code about as simple as it is now, maybe simpler; and still 
> take the same path as your patch for the 99% case where 
> characters() is 
> only called once. The hit wouldn't even be too bad when 
> characters() was 
> called more than once, because it almost never would be 
> called more than 
> two or three times. (Aside from the very weird #3 where performance 
> would be abysmal, but honestly that really requires an 
> updated parser.)
> 
> -- 
> ?Elliotte Rusty Harold  elharo AT metalab.unc.edu
> XML in a Nutshell 3rd Edition Just Published!
> http://www.cafeconleche.org/books/xian3/
> http://www.amazon.com/exec/obidos/ISBN=0596007647/cafeaulaitA/
ref=nosim
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