Add CRC32CHash.checksum property

This is not part of hashlib's interface, but it makes it easy to compare
the internal checksum kept by the hash object against an int value
provided somehow else.

Signed-off-by: Rodrigo Tobar <[email protected]>

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 * Added a `gil_relese_mode` parameter to the `CRC32CHash` constructor
   used by all underlying `crc32c` function calls (#51).
+* Added `CRC32CHash.checksum` auxiliary property.
 
 ## [2.6]
 

README.rst

@@ -59,13 +59,15 @@ It can be set to the following values:
 On top of the ``crc32c`` function,
 a ``CRC32CHash(data=b"", gil_release_mode=-1)`` class is also offered.
 It is modelled after the "hash objects" of the ``hashlib`` module
-of the standard library:
+of the standard library. It also offers a ``checksum`` property:
 
 .. code-block:: python
 
    crc32c_hash = crc32c.CRC32CHash()
    crc32c_hash.update(b'hello')
    crc32c_hash.update(b' world')
+   print(crc32c_hash.checksum == crc32c.crc32c(b'hello world'))
+   # True
    print(crc32c_hash.digest())
    # b'\xc9\x94e\xaa'
    digest_as_int = int.from_bytes(crc32c_hash.digest(), "big")

src/crc32c/__init__.py

@@ -36,6 +36,13 @@ def name(self) -> str:
         """
         return "crc32c"
 
+    @property
+    def checksum(self) -> int:
+        """
+        The checksum calculated so far. Not part of the hashlib interface.
+        """
+        return self._checksum
+
     def __init__(self, data: Buffer = b"", gil_release_mode: int = -1) -> None:
         """
         Initialise the hash object with an optional bytes-like object.

test/test_crc32c.py

@@ -174,6 +174,7 @@ def test_copy(self) -> None:
     class TestSpecificValues:
         @staticmethod
         def _check_values(crc32c_hash: crc32c.CRC32CHash, crc: int) -> None:
+            assert crc32c_hash.checksum == crc
             assert int.from_bytes(crc32c_hash.digest(), "big") == crc
             assert len(crc32c_hash.digest()) == 4
             assert int(crc32c_hash.hexdigest(), 16) == crc