Freelancer Hash Encoder

flhash.rb

require 'active_support/all'
require 'singleton'

class FLHash
  include Singleton

  FLHASH_POLYNOMIAL = 0xa001;
  LOGICAL_BITS = 30;
  PHYSICAL_BITS = 32;

  class << self
    delegate :encode, to: :instance
  end

  def initialize
    @table = []
    256.times do |index|
      x = index
      8.times do |bit|
        x = ((x & 1) == 1) ? (x >> 1) ^ (FLHASH_POLYNOMIAL << (LOGICAL_BITS - 16)) : x >> 1
      end
      @table[index] = x
    end
  end

  def encode(str)
    str = str.to_s.downcase.encode(Encoding::ASCII)
    hash = 0
    str.each_byte.with_index do |byte, index|
      hash = int32cast((hash >> 8) ^ @table[bytecast(hash) ^ byte])
    end
    hash = int32cast((hash >> 24) | ((hash >> 8) & 0x0000ff00) | ((hash << 8) & 0x00ff0000) | (hash << 24))
    hash = int32cast((hash >> (PHYSICAL_BITS - LOGICAL_BITS)) | 0x80000000)
    hash
  end

  private
  def bytecast(value)
    value & 0xff
  end

  def int32cast(value)
    value & 0xffffffff
  end
end