+ try:
+ import hashlib
+ self.hashlib = True
+ except ImportError:
+ self.hashlib = False
+ if algorithm == 'sha1':
+ import sha
+ self.hash_constructor = sha.new
+ elif algorithm == 'md5':
+ import md5
+ self.hash_constructor = md5.new
+ else:
+ raise NameError("Unknown algorithm '%s'" % algorithm)
+