Overview ==

This is a simple library for easily implementing parsers that are specified in Augmented Backus-Naur Form (ABNF). Many IETF RFCs specify protocols and other entities using ABNF. This library lets you use those core operators and rules almost directly as Ruby objects. An optional block can be specified for a rule. If the rule matches, it will pass the match into the block. This makes it possible to build up state as a parse progresses.

This version of the library was written to RFC 2234, which is an obsoleted version of the RFC. Not too much changed in the subsequent versions however. I'm hoping to do a pass through soon and make sure this library is compliant with RFC 5234.

Check out: tools.ietf.org/html/rfc5234 for more information.

Example ==

For a detailed example, tests/url.rb contains a full URL parser using the ABNF grammar from RFC 3986. It parses a URL from a string returns a structure containing the components.

Caveats ==

  • There's no lookahead, so when using Alternate, specify your longest matches first if one of the smaller alternative

matches could potentially fire.

  • It works on an 8-bit character basis - at least for now.