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>>reflect the reality that I repeatedly hear about: one can make significant >>optimizations in an implementation if there is some understanding that >>there will be no entities to expand. > > > What are these optimizations? If you know that you only have to do < and &, then you can do inplace substitutions: you don't have to have mechanisms for switching to some alternate buffer, copying and pasting "raw" input into a normalized buffer to pass back to the user, etc. When you see an & you can inline the character tests, not collecting the whole &...; into a lookup key, etc. If I'm not using SAX, but am instead doing some kind of XML tokenizer (perhaps to be used in by a SAX library), "zero-copy" could mean avoiding lots of work: I just pass the buffer back to the user directly. Yes, you can write an optimized codepath that does this, falling back (or falling over :) when it finds other entities, but it should be clear that if you *never* have those things, then your code can be smaller (and therefore more reliable), and faster. Make sense? /r$
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