def fingerprint(blob):
"""Compute the fingerprint of its input.
This blob can contain an integer, a string, a dict or
an object with a fingerprint method.
"""
# is it an integer?
try:
mpz_value = mpz(blob)
except (TypeError, ValueError):
pass
else:
string = utils.mpztob64(mpz_value)
return b64encode(crypthash(string).digest())
# is it a string?
if isinstance(blob, str):
return b64encode(crypthash(blob).digest())
# is it a list?
if isinstance(blob, (list, tuple)):
list_of_fingerprints = [fingerprint(i) for i in blob]
string = json.dumps(list_of_fingerprints, separators=(',', ':'))
return b64encode(crypthash(string).digest())
# is it a dict?
if isinstance(blob, dict):
# is this dict already a hash of something?
if "#" in blob:
return blob["#"]
# otherwise, transform dict into array and fingerprint it
keys = sorted(blob)
list_of_fingerprints = [fingerprint([k, blob[k]]) \
for k in keys]
string = json.dumps(list_of_fingerprints, separators=(',', ':'))
return b64encode(crypthash(string).digest())
# is it None
if blob is None:
return fingerprint('None')
# is it an object?
try:
# is it a class for which we can compute a fingerprint?
return blob.fingerprint()
except AttributeError:
pass
assert False, "fingerprint cannot parse object"
def fingerprint(self):
"""Compute the fingerprint of the object, as a base64 string.
It tries to not recompute the same hash many times by implementing
some tracking. However, this tracking only works for attributes.
As a result, it will for instance not detect changes in lists or dicts.
"""
# check whether the hash of this object is already known
if self.attr_fingerprint["#"] is not None:
return self.attr_fingerprint["#"]
list_to_hash = []
# Going through all fields that need to be taken into account
for key in sorted(self.to_fingerprint):
# Computing missing hashes
if self.attr_fingerprint[key] is None:
self.attr_fingerprint[key] = \
fingerprint([key, getattr(self, key)])
# Building final string
list_to_hash.append(self.attr_fingerprint[key])
string = json.dumps(list_to_hash, separators=(',', ':'))
result = b64encode(crypthash(string).digest())
self.attr_fingerprint["#"] = result
return result
