PCRE2

This library provides a Ruby interface for the PCRE2 library, which supports more advanced regular expression functionality than the built-in Ruby Regexp.

Why?

Ruby's Regexp is actually quite fast! For simple Regexps without backtracking (for instance regexp without matches like .*), you should probably keep using the Ruby Regexp. No extra dependencies and it'll be faster than using an external library, including PCRE2.

The main reason I built this was so I could use the backtracking control verbs such as (*SKIP)(*FAIL) that are not supported by Ruby's Regexp. Using these, and other features, PCRE2 supports some pretty wild and advanced regular expressions which you cannot do with Ruby's Regexp.

PCRE2 also supports JIT (just-in-time) compilation of the regular expression. From the manual:

Just-in-time compiling is a heavyweight optimization that can greatly speed up pattern matching. However, it comes at the cost of extra processing before the match is performed, so it is of most benefit when the same pattern is going to be matched many times. This does not necessarily mean many calls of a matching function; if the pattern is not anchored, matching attempts may take place many times at various positions in the subject, even for a single call. Therefore, if the subject string is very long, it may still pay to use JIT even for one-off matches.

You can enable JIT by calling regexp.jit! on the PCRE2::Regexp object. Using JIT the PCRE2 matching can be more than 2X faster than Ruby's built-in.

Installation

Install the PCRE2 library:

brew install pcre2

Add this line to your application's Gemfile:

gem'pcre2'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install pcre2

Usage

PCRE2::Regexp aims to act as much like Ruby's Regexp as possible. It has implemented a subset of the Regexp and MatchData APIs so it can be used as a drop-in replacement.

regexp=PCRE2::Regexp.new("hello")subject="well hello there!"matchdata=regexp.match(subject)matchdata.offset(0)# [5, 10] - start and end of the matchmatchdata[0]# => "hello"matchdata=regexp.match(subject,11)# find next match

Also some of the utility methods on String are reimplemented on PCRE2::Regexp:

regexp=PCRE2::Regexp.new('\d+')subject="and a 1 and a 2 and a 345"regexp.scan(subject)# => ["1", "2", "345"]regexp.split(subject)# => ["and a ", " and a ", " and a "]

There is one new method not available on Regexp: PCRE2::Regexp#matches which will loop over all matches of the string, and yield the corresponding Matchdata:

string="well hello hello hello there!"re=PCRE2::Regexp.new("hello")re.matches(string)do |matchdata|
puts"Matchdata found between #{matchdata.offsets(0)[0]} and #{matchdata.offsets(0)[1]}"end

Benchmark

You can run the benchmark that compares PCRE2::Regexp with Ruby's built-in Regexp as follows:

bundle exec rake benchmark

Resources

• PCRE2 Library
• PCRE2 demo

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/dv/pcre2.

License

The gem is available as open source under the terms of the MIT License.