10 Minute refactor

After a long weekend in the garden...

module Com_ravnaandtines
  module Zlib
    class Adler32
      # largest prime smaller than 65536
      @@ADLER_BASE = 65521
    
      def initialize
        @value = 1
      end
      
      def update(buffer)
        if not buffer
          return @value
        end
        ## build up the checksum
        low = @value & 0xffff
        high = (@value >> 16) & 0xffff
        buffer.each do |x| 
          low += (x.to_i & 0xff)
          high += low
        end

        ## collapse into modular parts
        low %= @@ADLER_BASE
        high %= @@ADLER_BASE
        @value = (high << 16) | low      
      end
      
      def reset
        @value = 1
      end
      
    end
  end
end

and tweak the tests thus:

  def basic_test_engine(seq, expected)
    ## string to array
    ## otherwise expect an each method to yield integers
    if seq.respond_to? :unpack
      seq = seq.unpack("C*")
    end
    adler = Com_ravnaandtines::Zlib::Adler32.new()
    a = adler.update(seq)
    assert_equal(expected, a)
  end

  def test_boundary
    basic_test_engine(nil, 1)  
  end

That feels better. No special cases, no leakage of state. Looking at JZlib, most of the work will be in doing the encapsulation properly.

Next up, though, when time and energy combine, more on the IronPython FTP client.