from lbrynet.dht import constants class Distance: """Calculate the XOR result between two string variables. Frequently we re-use one of the points so as an optimization we pre-calculate the value of that point. """ def __init__(self, key): if len(key) != constants.key_bits // 8: raise ValueError("invalid key length: %i" % len(key)) self.key = key self.val_key_one = int.from_bytes(key, 'big') def __call__(self, key_two): val_key_two = int.from_bytes(key_two, 'big') return self.val_key_one ^ val_key_two def is_closer(self, a, b): """Returns true is `a` is closer to `key` than `b` is""" return self(a) < self(b) def to_contact(self, contact): """A convenience function for calculating the distance to a contact""" return self(contact.id)