Added delete option to database storage.

venv/Lib/site-packages/google_crc32c/_checksum.py

@@ -0,0 +1,86 @@
+# Copyright 2020 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License 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.
+
+import struct
+
+
+class CommonChecksum(object):
+    """Hashlib-alike helper for CRC32C operations.
+
+    This class should not be used directly and requires an update implementation.
+
+    Args:
+        initial_value (Optional[bytes]): the initial chunk of data from
+            which the CRC32C checksum is computed.  Defaults to b''.
+    """
+
+    def __init__(self, initial_value=b""):
+        self._crc = 0
+        if initial_value != b"":
+            self.update(initial_value)
+
+    def update(self, data):
+        """Update the checksum with a new chunk of data.
+
+        Args:
+            chunk (Optional[bytes]): a chunk of data used to extend
+                the CRC32C checksum.
+        """
+        raise NotImplemented()
+
+    def digest(self):
+        """Big-endian order, per RFC 4960.
+
+        See: https://cloud.google.com/storage/docs/json_api/v1/objects#crc32c
+
+        Returns:
+            bytes: An eight-byte digest string.
+        """
+        return struct.pack(">L", self._crc)
+
+    def hexdigest(self):
+        """Like :meth:`digest` except returns as a bytestring of double length.
+
+        Returns
+            bytes: A sixteen byte digest string, contaiing only hex digits.
+        """
+        return "{:08x}".format(self._crc).encode("ascii")
+
+    def copy(self):
+        """Create another checksum with the same CRC32C value.
+
+        Returns:
+            Checksum: the new instance.
+        """
+        clone = self.__class__()
+        clone._crc = self._crc
+        return clone
+
+    def consume(self, stream, chunksize):
+        """Consume chunks from a stream, extending our CRC32 checksum.
+
+        Args:
+            stream (BinaryIO): the stream to consume.
+            chunksize (int): the size of the read to perform
+
+        Returns:
+            Generator[bytes, None, None]: Iterable of the chunks read from the
+            stream.
+        """
+        while True:
+            chunk = stream.read(chunksize)
+            if not chunk:
+                break
+            self.update(chunk)
+            yield chunk