Filter expressions

[ato]

Parse a very simple filter expression language with Ragel?

use-cases:

• jwarc filter image ex.warc > images.warc
• jwarc recorder | jwarc filter 'http.method != HEAD' > record.warc
• jwarc filter !error ex.warc | jwarc unpack
• parameterizing your own tools or analysis jobs with a filter

operators:

! not
==, != string equality
~= regex match
<, <=, >=, > numeric comparison
&&, || boolean logic

shorthand predicates:

resource: WARC-Type == resource || WARC-Type == response
page: resource && payload.type == text/html
image: resource && payload.type ~= ^image/
error: WARC-Type == response && http.status > 400