fixes sha1#update bug on OSX

patch.rb

require 'digest/sha1'

# this patch fixes SHA1#update on OSX
class Digest::SHA1

  def update s
    buf_size = 1024 ** 2

    if s.size > buf_size
      io = StringIO.new s
      buf = String.new
      super buf while io.read(buf_size, buf)
    else
      super s
    end

  end

end