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View Code? Open in Web Editor NEWThis is a library to convert ABNF (Augmented Backus-Naur Form) to Regexp (Regular Expression) written in Ruby.
Home Page: http://www.a-k-r.org/abnf/
This is a library to convert ABNF (Augmented Backus-Naur Form) to Regexp (Regular Expression) written in Ruby.
Home Page: http://www.a-k-r.org/abnf/
= abnf This is a library to convert ABNF (Augmented Backus-Naur Form) to Regexp (Regular Expression) written in Ruby. It parses a description according to ABNF defined by RFC2234 and some variants. Then the parsed grammar is transformed to recursion free. Although the transformation is impossible in general, the library transform left- and right-recursion. The recursion free grammar can be printed as Regexp literal which is suitable in Ruby script. The literal is pretty readable because parentheses are minimized and properly indented by the Wadler's pretty printing algebra. It is also possible to use the Regexp just in place. == Author Tanaka Akira <[email protected]> == Home Page http://www.a-k-r.org/abnf/ == Example Following example shows URI-reference defined by RFC 2396 can be converted to Regexp. Note that URI-reference has no recursion. Also note that the example works well without installing the library after make. require 'pp' require 'abnf' # URI-reference [RFC2396] pp ABNF.regexp_tree(<<-'End') URI-reference = [ absoluteURI | relativeURI ] [ "#" fragment ] absoluteURI = scheme ":" ( hier_part | opaque_part ) relativeURI = ( net_path | abs_path | rel_path ) [ "?" query ] (...snip...) lowalpha = "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h" | "i" | "j" | "k" | "l" | "m" | "n" | "o" | "p" | "q" | "r" | "s" | "t" | "u" | "v" | "w" | "x" | "y" | "z" upalpha = "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H" | "I" | "J" | "K" | "L" | "M" | "N" | "O" | "P" | "Q" | "R" | "S" | "T" | "U" | "V" | "W" | "X" | "Y" | "Z" digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" End The result is follows: %r{(?:[a-z][\x2b\x2d\x2e0-9a-z]*: (?:(?:// (?:(?:(?:(?:[!'-\x2a\x2d\x2e0-9_a-z~]| %[0-9a-f][0-9a-f]| [\x24&\x2b,:;=])*@)? (?:(?:(?:[0-9a-z]|[0-9a-z][\x2d0-9a-z]*[0-9a-z])\x2e)* (?:[a-z]|[a-z][\x2d0-9a-z]*[0-9a-z])\x2e?| \d+\x2e\d+\x2e\d+\x2e\d+)(?::\d*)?)?| (?:[!'-\x2a\x2d\x2e0-9_a-z~]| %[0-9a-f][0-9a-f]| [\x24&\x2b,:;=@])+) (?:/ (?:[!'-\x2a\x2d\x2e0-9_a-z~]|%[0-9a-f][0-9a-f]|[\x24&\x2b,:=@])* (?:; (?:[!'-\x2a\x2d\x2e0-9_a-z~]| %[0-9a-f][0-9a-f]| [\x24&\x2b,:=@])*)* (?:/ (?:[!'-\x2a\x2d\x2e0-9_a-z~]| %[0-9a-f][0-9a-f]| [\x24&\x2b,:=@])* (?:; (?:[!'-\x2a\x2d\x2e0-9_a-z~]| %[0-9a-f][0-9a-f]| [\x24&\x2b,:=@])*)*)*)?| /(?:[!'-\x2a\x2d\x2e0-9_a-z~]|%[0-9a-f][0-9a-f]|[\x24&\x2b,:=@])* (?:; (?:[!'-\x2a\x2d\x2e0-9_a-z~]| %[0-9a-f][0-9a-f]| [\x24&\x2b,:=@])*)* (?:/ (?:[!'-\x2a\x2d\x2e0-9_a-z~]|%[0-9a-f][0-9a-f]|[\x24&\x2b,:=@])* (?:; (?:[!'-\x2a\x2d\x2e0-9_a-z~]| %[0-9a-f][0-9a-f]| [\x24&\x2b,:=@])*)*)*) (?:\x3f(?:[!\x24&-;=\x3f@_a-z~]|%[0-9a-f][0-9a-f])*)?| (?:[!'-\x2a\x2d\x2e0-9_a-z~]|%[0-9a-f][0-9a-f]|[\x24&\x2b,:;=\x3f@]) (?:[!\x24&-;=\x3f@_a-z~]|%[0-9a-f][0-9a-f])*)| (?:// (?:(?:(?:(?:[!'-\x2a\x2d\x2e0-9_a-z~]| %[0-9a-f][0-9a-f]| [\x24&\x2b,:;=])*@)? (?:(?:(?:[0-9a-z]|[0-9a-z][\x2d0-9a-z]*[0-9a-z])\x2e)* (?:[a-z]|[a-z][\x2d0-9a-z]*[0-9a-z])\x2e?| \d+\x2e\d+\x2e\d+\x2e\d+)(?::\d*)?)?| (?:[!'-\x2a\x2d\x2e0-9_a-z~]|%[0-9a-f][0-9a-f]|[\x24&\x2b,:;=@])+) (?:/(?:[!'-\x2a\x2d\x2e0-9_a-z~]|%[0-9a-f][0-9a-f]|[\x24&\x2b,:=@])* (?:; (?:[!'-\x2a\x2d\x2e0-9_a-z~]| %[0-9a-f][0-9a-f]| [\x24&\x2b,:=@])*)* (?:/ (?:[!'-\x2a\x2d\x2e0-9_a-z~]|%[0-9a-f][0-9a-f]|[\x24&\x2b,:=@])* (?:; (?:[!'-\x2a\x2d\x2e0-9_a-z~]| %[0-9a-f][0-9a-f]| [\x24&\x2b,:=@])*)*)*)?| /(?:[!'-\x2a\x2d\x2e0-9_a-z~]|%[0-9a-f][0-9a-f]|[\x24&\x2b,:=@])* (?:;(?:[!'-\x2a\x2d\x2e0-9_a-z~]|%[0-9a-f][0-9a-f]|[\x24&\x2b,:=@])*)* (?:/(?:[!'-\x2a\x2d\x2e0-9_a-z~]|%[0-9a-f][0-9a-f]|[\x24&\x2b,:=@])* (?:; (?:[!'-\x2a\x2d\x2e0-9_a-z~]| %[0-9a-f][0-9a-f]| [\x24&\x2b,:=@])*)*)*| (?:[!'-\x2a\x2d\x2e0-9_a-z~]|%[0-9a-f][0-9a-f]|[\x24&\x2b,;=@])+ (?:/(?:[!'-\x2a\x2d\x2e0-9_a-z~]|%[0-9a-f][0-9a-f]|[\x24&\x2b,:=@])* (?:; (?:[!'-\x2a\x2d\x2e0-9_a-z~]| %[0-9a-f][0-9a-f]| [\x24&\x2b,:=@])*)* (?:/ (?:[!'-\x2a\x2d\x2e0-9_a-z~]|%[0-9a-f][0-9a-f]|[\x24&\x2b,:=@])* (?:; (?:[!'-\x2a\x2d\x2e0-9_a-z~]| %[0-9a-f][0-9a-f]| [\x24&\x2b,:=@])*)*)*)?) (?:\x3f(?:[!\x24&-;=\x3f@_a-z~]|%[0-9a-f][0-9a-f])*)?)? (?:\x23(?:[!\x24&-;=\x3f@_a-z~]|%[0-9a-f][0-9a-f])*)?}xi Following example contains right-recursion: pp ABNF.regexp_tree(<<'End') s0 = n0 s0 / n1 s2 / n2 s1 / "" s1 = n0 s1 / n1 s0 / n2 s2 s2 = n0 s2 / n1 s1 / n2 s0 n0 = "0" / "3" / "6" / "9" n1 = "1" / "4" / "7" n2 = "2" / "5" / "8" End The above ABNF description represents decimal numbers which are multiples of 3 and the result is follows: %r{(?:[0369]| [147](?:[0369]|[147][0369]*[258])*(?:[147][0369]*[147]|[258])| [258][0369]* (?:[147]| [258](?:[0369]|[147][0369]*[258])*(?:[147][0369]*[147]|[258])))*}xi A converted regexp can be used to match in place as: p /\A#{ABNF.regexp <<'End'}\z/o =~ "::13.1.68.3" IPv6address = "::" / 7( hex4 ":" ) hex4 / 1*8( hex4 ":" ) ":" / 7( hex4 ":" ) ( ":" hex4 ) / 6( hex4 ":" ) 1*2( ":" hex4 ) / 5( hex4 ":" ) 1*3( ":" hex4 ) / 4( hex4 ":" ) 1*4( ":" hex4 ) / 3( hex4 ":" ) 1*5( ":" hex4 ) / 2( hex4 ":" ) 1*6( ":" hex4 ) / ( hex4 ":" ) 1*7( ":" hex4 ) / ":" 1*8( ":" hex4 ) / 6( hex4 ":" ) IPv4address / 6( hex4 ":" ) ":" IPv4address / 5( hex4 ":" ) ":" 0*1( hex4 ":" ) IPv4address / 4( hex4 ":" ) ":" 0*2( hex4 ":" ) IPv4address / 3( hex4 ":" ) ":" 0*3( hex4 ":" ) IPv4address / 2( hex4 ":" ) ":" 0*4( hex4 ":" ) IPv4address / ( hex4 ":" ) ":" 0*5( hex4 ":" ) IPv4address / "::" 0*6( hex4 ":" ) IPv4address IPv4address = 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT hex4 = 1*4HEXDIG End == Document * abnf.html : abnf.rb reference manual * regexptree.html : regexptree.rb reference manual * natset.html : natset.rb reference manual == Requirements * ruby-1.7.3 (2002-10-08) (older version doesn't work.) * racc-1.3.11 (older version may work.) == Download * latest release: http://www.a-k-r.org/abnf/abnf-0.6.tar.gz * development version: https://github.com/akr/abnf == Install % make % mkdir /usr/local/lib/ruby/site_ruby/abnf % cp abnf/*.rb /usr/local/lib/ruby/site_ruby/abnf % cp abnf.rb natset.rb regexptree.rb /usr/local/lib/ruby/site_ruby == License Ruby's
ABNF is usually case sensitive, right?
While the standard suggests it is illegal to use string literals "a" / "b"
and instead to escape them in to unreadable muck, many people use them anyway.
In these (common) cases, it is often correct to respect the input case.
.regex always seems to return /something/i
.
I suppose this may be a workaround for bad input, but at least an option to stop it would be cute.
If I define two times the same entity, it extends the previous entity.
For example:
a = "a"
a = "b"
Expected result: "b", "a" or (preferably) error.
Result:
%r{[ab]}xi
Maybe this is correct or documented, however it doesn't match my expectation. (I was under the impression in the RFC you have to use a special operator for extension, not =
but rather *=
or something similar.)
Thanks heaps for this library by the way, it is gold!
print "Regexp for A to C: "
pp ABNF.regexp_tree(<<-'End').to_s
a-to-c="abc"
End
Expected output: Regexp for A to C: "[abc]"
or maybe ... "/[abc]/"
Observed output: Regexp for A to C: "(?i-m:abc)"
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