Source code for pyqldb.util.qldb_hash

# Copyright 2019, Inc. or its affiliates. All Rights Reserved.
# Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance with
# the License. A copy of the License is located at
# or in the "license" file accompanying this file. This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
# CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions
# and limitations under the License.
from array import array
from hashlib import sha256

from amazon.ion.simpleion import loads, dumps
import ionhash


[docs]class QldbHash: """ A QLDB hash is either a 256 bit number or a special empty hash. :raises ValueError: When the hash is None or is not the correct hash size. """ def __init__(self, qldb_hash): if qldb_hash is None or (len(qldb_hash) != HASH_SIZE and len(qldb_hash) != 0): raise ValueError('Hash must either be empty or {} bytes long'.format(HASH_SIZE)) self._qldb_hash = qldb_hash def __eq__(self, other): if not isinstance(other, QldbHash) or other is None: return False return QldbHash._hash_comparator(self.get_qldb_hash(), other.get_qldb_hash()) == 0 def __repr__(self): return self._qldb_hash.hex()
[docs] def dot(self, that): """ Sort the current hash value and the hash value provided by `that`, comparing by their **signed** byte values in little-endian order. :type that: bytes :param that: The Ion hash of Ion value to compare. :rtype: :py:class:`pyqldb.util.qldb_hash.Qldbhash`/object :return: An QldbHash object that contains the concatenated hash values. """ concatenated = QldbHash._join_hashes_pair_wise(self.get_qldb_hash(), that.get_qldb_hash()) new_hash_lib = sha256() new_hash_lib.update(concatenated) new_digest = new_hash_lib.digest() return QldbHash(new_digest)
[docs] def get_hash_size(self): return len(self._qldb_hash)
[docs] def get_qldb_hash(self): return self._qldb_hash
[docs] def is_empty(self): return len(self._qldb_hash) == 0
[docs] @staticmethod def to_qldb_hash(value): """ The QldbHash of an IonValue is just the IonHash of that value. :type value: str/:py:class:`amazon.ion.simple_types.IonSymbol` :param value: The string or Ion value to be converted to Ion hash. :rtype: :py:class:`pyqldb.util.qldb_hash.Qldbhash`/object :return: An QldbHash object that contains Ion hash. """ if isinstance(value, str): value = loads(dumps(value)) ion_hash = value.ion_hash('SHA256') ion_hash_digest = ion_hash return QldbHash(ion_hash_digest)
@staticmethod def _hash_comparator(h1, h2): """ Compares two hashes by their **signed** byte values in little-endian order. """ h1_array = array('b', h1) h2_array = array('b', h2) if len(h1) != 32 or len(h2) != 32: raise ValueError("Invalid hash") for i in range(len(h1_array) - 1, -1, -1): difference = h1_array[i] - h2_array[i] if difference != 0: return difference return 0 @staticmethod def _join_hashes_pair_wise(h1, h2): """ Takes two hashes, sorts them, and concatenates them. """ if len(h1) == 0: return h2 if len(h2) == 0: return h1 if QldbHash._hash_comparator(h1, h2) < 0: concatenated = h1 + h2 else: concatenated = h2 + h1 return concatenated