unmasking_benchmark.rb

# gem install fast_xor
module EventMachine
  module WebSocket
    class MaskedString < String
      def read_mask
        raise "Too short" if bytesize < 4 # TODO - change
        @masking_key = String.new(self[0..3])
      end

      def full_mask(start, length)
        first_mask = start % 4
        mask_multiplier = length / 4 + 1
        (@masking_key * mask_multiplier)[first_mask..-1]
      end

      def getbytes(start_index, count)
        string_to_mask = self[start_index..start_index + count]
        masking_string = full_mask(start_index, count)
        string_to_mask.xor!(masking_string)
      end
    end
  end
end

require 'benchmark'
require 'xor'

n = 1000

# Use a 4 byte mask and a 1K string
string = rand.to_s[0..3] + 'a' * 1024

Benchmark.bm do |x|
  x.report("MaskedString:") {
    n.times {
      string = EventMachine::WebSocket::MaskedString.new(string)
      string.read_mask
      string.getbytes(0, 1024)
    }
  }
end