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Posted to dev@daffodil.apache.org by "Steve Lawrence (JIRA)" <ji...@apache.org> on 2018/03/13 14:44:00 UTC

[jira] [Created] (DAFFODIL-1917) Support for new character classes

Steve Lawrence created DAFFODIL-1917:
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             Summary: Support for new character classes
                 Key: DAFFODIL-1917
                 URL: https://issues.apache.org/jira/browse/DAFFODIL-1917
             Project: Daffodil
          Issue Type: New Feature
          Components: Back End, Front End, Middle &quot;End&quot;
            Reporter: Steve Lawrence
             Fix For: deferred


Daffodil v2.0 wishlist includes new character class entities LSP, LSP* and LSP+, which are the same as WSP except they do not match line endings. This is useful as currently it is impossible to match an empty line followed by a newline via something like %WSP*;%NL; due to the greediness of WSP* and the inability for our delimiter scanner to backtrack of forward lookahead.

Related, it might be useful to also add NL+ and NL* to match an unbounded number of newlines.

Additionally, it might be a good idea to cause an SDE if a character class that contains * or
+ is immediately followed by a character inside that character class. The reason being that such sequences will always fail without lookahead or backtracking, which probalby isn't worth implementing.

For security reasons, we should also implement a tunable to limit the number or repetitions of these character entities.



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