I had started porting CTClib to managed C++ to do an Iron<something> piecemeal conversion. But at the moment IronPython doesn't have a good deployment story, IronRuby isn't all there; and I still much prefer Java's UI model to WinForms or WPF… So what about JRuby -- familiar UI style and run from jar -- then?
The stumbling block as always is PhilZ's choice of deflate with a 2^13 bit window (as opposed to Zlib's fixed 2^15 bit window size for Ruby or java.util.zip) for compression. This was where I paused my first Java port -- JZlib which could do the job has appeared since I last looked, around the turn of the century. Even so, for sake of portability I've decided to bite the bullet, and do a minimal zlib/deflate implementation in Ruby for the purpose, to do something meaningful with the language, using JZlib as a guide. Inflate can, of course, have the larger window (as in current CTClib-C builds), and use the built-in version, be it the C version from native Ruby or JRuby's java.util.zip wrapper.
So, the easy bit first -- Adler 32 checksum…
module Com_ravnaandtines
module Zlib
# largest prime smaller than 65536
ADLER_BASE = 65521
# Adler32 checksum : takes a seed (usually 1), and a byte sequence,
# returns 32-bit integer
def adler32(adler, buffer)
if not buffer
return 1
end
## string to array
## otherwise expect an each method to yield integers
if buffer.respond_to? :unpack
buffer = buffer.unpack("C*")
end
## build up the checksum
low = adler & 0xffff
high = (adler >> 16) & 0xffff
buffer.each do |x|
low += (x.to_i & 0xff)
high += low
end
## collapse into modular parts
low %= ADLER_BASE
high %= ADLER_BASE
(high << 16) | low
end
end
end
Test vectors for the unit tests had to be scavenged from the internet:
require 'test/unit'
require 'tinesware_zlib'
include Com_ravnaandtines::Zlib
class AdlerTest < Test::Unit::TestCase
def basic_test_engine(seq, expected)
a = Com_ravnaandtines::Zlib.adler32(1, seq)
assert_equal(expected, a)
end
def test_boundary
a = Com_ravnaandtines::Zlib.adler32(0, nil)
assert_equal(1, a)
end
def test_simple_0
basic_test_engine("Mark Adler", 0x13070394)
end
def test_simple_1
basic_test_engine("\x00\x01\x02\x03", 0x000e0007)
end
def test_simple_2
basic_test_engine("\x00\x01\x02\x03\x04\x05\x06\x07", 0x005c001d)
end
def test_simple_3
basic_test_engine("\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f", 0x02b80079)
end
def test_simple_4
basic_test_engine("\x41\x41\x41\x41", 0x028e0105)
end
def test_simple_5
basic_test_engine("\x42\x42\x42\x42\x42\x42\x42\x42", 0x09500211)
end
def test_simple_6
basic_test_engine("\x43\x43\x43\x43\x43\x43\x43\x43\x43\x43\x43\x43\x43\x43\x43\x43", 0x23a80431)
end
class Vector #arrays filled with value = (byte) index
def initialize(size)
@size = size
end
def each
index = 0
while index < @size
yield index & 0xff
index += 1
end
end
end
def test_total
index = 0
results = [ 486795068,
1525910894,
3543032800,
2483946130,
4150712693,
3878123687,
3650897945,
1682829244,
1842395054,
460416992,
3287492690,
479453429,
3960773095,
2008242969,
4130540683,
1021367854,
4065361952,
2081116754,
4033606837,
1162071911 ]
while index < 20
size = 5*index + 1
xx = Vector.new(1000*size)
basic_test_engine(xx, results[index])
index += 1
end
end
end
That was one evening. Now, how long will the rest of it take?
