string_gzip_extension.rb

require 'zlib'

class String
  def gzip
    io = StringIO.new
    gz = Zlib::GzipWriter.new(io)
    gz.write(self)
    gz.close
    io.string
  end

  def gzip!
    replace gzip
  end

  def gunzip
    Zlib::GzipReader.new(StringIO.new(self)).read
  rescue Zlib::GzipFile::Error
    self
  end

  def gunzip!
    replace gunzip
  end
end