# This is built on the discussion at 
# from http://effbot.org/zone/python-hash.htm

# See http://docs.python.org/reference/datamodel.html
# for special python method names like __getitem__

DEBUG = False

def c_mul(a, b):
  """ Multiply two numbers the way C does """
  ## 32 bit long
  # return eval(hex((long(a) * b) & 0xFFFFFFFFL)[:-1])
  ## 64 bit long
  return eval(hex((long(a) * b) & 0xFFFFFFFFFFFFFFFFL)[:-1])

class FakeString(object):
  def __init__(self, string=""):
    self.string = string
  def __getitem__(self, i):
    return self.string[i]
  def __len__(self):
    return len(self.string)
  def __str__(self):
    return self.string
  def __hash__(self):
    # 1000003 is smallest prime bigger than a million
    if not self:
      return 0 # empty
    value = ord(self[0]) << 7
    if DEBUG: print "debug: value = %i" % value
    for char in self:
      # ^ is the bitwise xor operator
      value = c_mul(1000003, value) ^ ord(char)
      if DEBUG: print "debug: value = %i" % value
    value = value ^ len(self)
    if DEBUG: print "debug: value = %i" % value
    if value == -1:
      value = -2
    return value
  
if __name__ == "__main__":
  s = FakeString("foo")
  h = hash(s)
  print "hash('%s') = %i" % (s, h)