Metamarshal

Have you ever been confronted by a non-loadable marshal data? Metamarshal may help you!

For example, from Rails 4.2 to Rails 5.0, the class ActionController::Parameters stopped inheriting ActiveSupport::HashWithIndifferentAccess (and Hash transitively). This means that if you were using Marshal cookie sessions and you were (perhaps accidentally) saving ActionController::Parameters in your session storage, the session may break with undecipherable error message.

Metamarshal is a pure Ruby "parser" for the marshal format. It allows parsing the marshal data without actually trying to realize it as the corresponding Ruby object. Instead, it can output a syntax tree (or a syntax graph in a complex case) so you can modify it before realization.

Metamarshal is totally work-in-progress for now:

• Parsing
  • nil (0), true (T), false (F)
  • Fixnum
  • Subclasses of String/Regexp/Array/Hash (C)
  • Old user-defined marshal data (u)
  • User-defined marshal data (U)
  • User-defined marshal data for TData (d)
  • Plain object (o)
  • Float (f)
  • Bignum (l)
  • String (")
  • Regexp (/)
  • Array ([)
  • Hash without default value ({)
  • Hash with default value (})
  • Struct (S)
  • Old Class or Module (M)
  • Class (c)
  • Module but not Class (m)
  • Symbol (:)
    • encoded symbols
  • Symbol link (;)
  • Extension of an object by a module (e)
  • Instance variables of String/Regexp/Array/Hash (I)
  • link (@)
• Generation
  • nil (0), true (T), false (F)
  • Fixnum
  • Subclasses of String/Regexp/Array/Hash (C)
  • Old user-defined marshal data (u)
  • User-defined marshal data (U)
  • User-defined marshal data for TData (d)
  • Plain object (o)
  • Float (f)
  • Bignum (l)
  • String (")
  • Regexp (/)
  • Array ([)
  • Hash without default value ({)
  • Hash with default value (})
  • Struct (S)
  • Old Class or Module (M)
  • Class (c)
  • Module but not Class (m)
  • Symbol (:)
    • encoded symbols
  • Symbol link (;)
  • Extension of an object by a module (e)
  • Instance variables of String/Regexp/Array/Hash (I)
  • link (@)
• Realization
• Lifting
• Feature
  • Iterate over parsed objects
  • Marshal-compatible load/dump interface

Installation

Add this line to your application's Gemfile:

gem 'metamarshal'

And then execute:

$ bundle

Or install it yourself as:

$ gem install metamarshal

Usage

TODO: Write usage instructions here

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test 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/qnighy/metamarshal.

License

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