On Dec 7, 2009, at 8:56 AM, Maciej Stachowiak wrote:
Actually, this is potentially a factor for any natively supported
AST format. If execution is direct rather than via transoformation
to JS source, the implementation would have to verify that the AST
is one that could be created by parsing JS source.
This reminds me of SafeTSA:
http://portal.acm.org/citation.cfm?id=378825
http://portal.acm.org/citation.cfm?doid=1377492.1377496
and more specifically of work by Christian Stork and Michael Franz, see:
http://www.ics.uci.edu/~cstork/
The idea as I first heard it from Chris and Michael was to
arithmetically code ASTs such that no ill-formed tree could be
encoded. You could take a JPEG of the Mona Lisa, run it through the
decoder, and if it succeeded, get a (almost-certainly) nonsensical yet
syntactically well-formed AST. The encoding is fairly efficient, not
as good as optimized Huffman coding but close.
This work was motivated by the sometimes bad (O(n^4)) complexity in
the Java bytecode verifier (or at least in early versions of it).
My view is that there will never be a standardized bytecode (politics
look insuperable to me), and more: that there should not be. Besides
the conflicts among target VM technical details, and ignoring latent
IPR issues, I believe view-source capability is essential. Even
minification lets one pretty-print (http://jsbeautifier.org/) and
learn or diagnose.
JS is still used in edit-shift-reload, crawl-walk-run development
style and part of this culture involves sharing. Of course no one
could mandate binary syntax to the exclusion of source, but a binary
syntax that did not allow pretty-printing would shove us all down the
slippery slope toward the opaque, closed-box world of Java applets,
Flash SWFs (modulo Flash+Flex's server-fetched view-source
capabilities), etc.
Compression at the transport (session, whatever, the model is climbing
the traditional layering) is a separate issue.
/be
_______________________________________________
es-discuss mailing list
[email protected]
https://mail.mozilla.org/listinfo/es-discuss
