Use hardware accelerated CRC32C function if available (#1389)

* Use hardware accelerated CRC32C function if available

* Add doc notice of optional `crc32c` package

4 files changed, 28 insertions, 5 deletions

diff --git a/docs/install.rst b/docs/install.rst
index cc0e82d..fe740f6 100644
--- a/docs/install.rst
+++ b/docs/install.rst
@@ -70,3 +70,16 @@ Install the `python-snappy` module
 .. code:: bash
 
     pip install python-snappy
+
+
+Optional crc32c install
+***********************
+Highly recommended if you are using Kafka 11+ brokers. For those `kafka-python`
+uses a new message protocol version, that requires calculation of `crc32c`,
+which differs from `zlib.crc32` hash implementation. By default `kafka-python`
+calculates it in pure python, which is quite slow. To speed it up we optionally
+support https://pypi.python.org/pypi/crc32c package if it's installed.
+
+.. code:: bash
+
+    pip install crc32c
diff --git a/kafka/record/util.py b/kafka/record/util.py
index 55d7adb..74b9a69 100644
--- a/kafka/record/util.py
+++ b/kafka/record/util.py
@@ -1,6 +1,10 @@
 import binascii
 
 from kafka.record._crc32c import crc as crc32c_py
+try:
+    from crc32c import crc32 as crc32c_c
+except ImportError:
+    crc32c_c = None
 
 
 def encode_varint(value, write):
@@ -113,11 +117,15 @@ def decode_varint(buffer, pos=0):
             raise ValueError("Out of int64 range")
 
 
-def calc_crc32c(memview):
+_crc32c = crc32c_py
+if crc32c_c is not None:
+    _crc32c = crc32c_c
+
+
+def calc_crc32c(memview, _crc32c=_crc32c):
     """ Calculate CRC-32C (Castagnoli) checksum over a memoryview of data
     """
-    crc = crc32c_py(memview)
-    return crc
+    return _crc32c(memview)
 
 
 def calc_crc32(memview):
diff --git a/test/record/test_util.py b/test/record/test_util.py
index bfe0fcc..0b2782e 100644
--- a/test/record/test_util.py
+++ b/test/record/test_util.py
@@ -68,9 +68,10 @@ def test_size_of_varint(encoded, decoded):
     assert util.size_of_varint(decoded) == len(encoded)
 
 
-def test_crc32c():
+@pytest.mark.parametrize("crc32_func", [util.crc32c_c, util.crc32c_py])
+def test_crc32c(crc32_func):
     def make_crc(data):
-        crc = util.calc_crc32c(data)
+        crc = crc32_func(data)
         return struct.pack(">I", crc)
     assert make_crc(b"") == b"\x00\x00\x00\x00"
     assert make_crc(b"a") == b"\xc1\xd0\x43\x30"
diff --git a/tox.ini b/tox.ini
index 0f1aaf4..35dc842 100644
--- a/tox.ini
+++ b/tox.ini
@@ -18,6 +18,7 @@ deps =
     python-snappy
     lz4
     xxhash
+    crc32c
     py26: unittest2
 commands =
     py.test {posargs:--pylint --pylint-rcfile=pylint.rc --pylint-error-types=EF --cov=kafka --cov-config=.covrc}