msgpack_pure.rb

require "stringio"

module MessagePackPure
  def self.unpack(binary)
    io = StringIO.new(binary)
    return self.read(io)
  end

  def self.read(io)
    type = io.read(1).unpack("C")[0]

    if (type & 0b10000000) == 0b00000000 # positive fixnum
      return type
    elsif (type & 0b11100000) == 0b10100000 # fixraw
      size = (type & 0b00011111)
      return io.read(size)
    elsif (type & 0b11110000) == 0b10010000 # fixarray
      size = (type & 0b00001111)
      return size.times.map { read(io) }
    end

    case type
    when 0xC0 then nil
    when 0xCB # double
      return io.read(8).unpack("G")[0]
    when 0xCC # uint8
      return io.read(1).unpack("C")[0]
    when 0xDE # map16
      size = io.read(2).unpack("n")[0]
      ary = size.times.map {
        key = read(io)
        value = read(io)
        [key, value]
      }
      return Hash[ary]
    else raise("Unknown Type -- #{'0x%02X' % type}")
    end
  end
end

if $0 == __FILE__
  require "test/unit"
  require "rubygems"
  require "msgpack"

  class MessagePackPureTest < Test::Unit::TestCase
    def setup
      @module = MessagePackPure
    end

    def test_nil
      assert_equal(nil, @module.unpack(MessagePack.pack(nil)))
    end

    def test_positive_fixnum
      (0..127).each { |n|
        assert_equal(n, @module.unpack(MessagePack.pack(n)))
      }
    end

    def test_uint8
      assert_equal(128, @module.unpack(MessagePack.pack(128)))
      assert_equal(2 ** 8 - 1, @module.unpack(MessagePack.pack(2 ** 8 - 1)))
    end

    def test_map16
      map = {}
      (1..16).each { |i| map[i] = i }
      assert_equal(map, @module.unpack(MessagePack.pack(map)))
    end

    def test_fixraw
      assert_equal("", @module.unpack(MessagePack.pack("")))
      assert_equal("a", @module.unpack(MessagePack.pack("a")))
    end

    def test_fixarray
      assert_equal([], @module.unpack(MessagePack.pack([])))
      assert_equal([1], @module.unpack(MessagePack.pack([1])))
    end

    def test_double
      assert_equal(0.5, @module.unpack(MessagePack.pack(0.5)))

    end
  end
end