From 64c4cca70f3b10d7e6a8bead7f415edd451bf66e Mon Sep 17 00:00:00 2001
From: Joseph Hamman <joe@earthmover.io>
Date: Wed, 8 Oct 2025 20:58:15 -0700
Subject: [PATCH 1/3] chore(crc32c): replace crc32c with google-crc32c
 dependency

---
 .pre-commit-config.yaml |  2 +-
 numcodecs/checksum32.py | 10 ++++++++--
 pyproject.toml          |  2 +-
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index c08b8f8a..723e0a85 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -30,4 +30,4 @@ repos:
       hooks:
       -   id: mypy
           args: [--config-file, pyproject.toml]
-          additional_dependencies: [numpy, pytest, crc32c, zfpy, 'zarr>=3']
+          additional_dependencies: [numpy, pytest, google-crc32c, zfpy, 'zarr>=3']
diff --git a/numcodecs/checksum32.py b/numcodecs/checksum32.py
index b7d5bf0b..9ecf212e 100644
--- a/numcodecs/checksum32.py
+++ b/numcodecs/checksum32.py
@@ -14,7 +14,7 @@
 
 _crc32c: ModuleType | None = None
 with suppress(ImportError):
-    import crc32c as _crc32c  # type: ignore[no-redef, unused-ignore]
+    import google_crc32c as _crc32c  # type: ignore[no-redef, unused-ignore]
 
 CHECKSUM_LOCATION = Literal['start', 'end']
 
@@ -179,5 +179,11 @@ class CRC32C(Checksum32):
         """
 
         codec_id = 'crc32c'
-        checksum = _crc32c.crc32c  # type: ignore[union-attr]
         location = 'end'
+
+        @staticmethod
+        def checksum(data: Buffer, value: int = 0) -> int:
+            if value == 0:
+                return _crc32c.value(data)  # type: ignore[union-attr]
+            else:
+                return _crc32c.extend(value, data)  # type: ignore[union-attr]
diff --git a/pyproject.toml b/pyproject.toml
index c925cd17..68aef3fe 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -72,7 +72,7 @@ pcodec = [
     "pcodec>=0.3,<0.4",
 ]
 crc32c = [
-    "crc32c>=2.7",
+    "google-crc32c>=1.5",
 ]
 
 [project.entry-points."zarr.codecs"]

From 61d7e148d26a0c0472e0aa6c6d588819f64721d2 Mon Sep 17 00:00:00 2001
From: Joseph Hamman <joe@earthmover.io>
Date: Wed, 8 Oct 2025 21:26:28 -0700
Subject: [PATCH 2/3] add incremental checksum test

---
 numcodecs/tests/test_checksum32.py | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/numcodecs/tests/test_checksum32.py b/numcodecs/tests/test_checksum32.py
index 9bdc25cb..b2d91cf0 100644
--- a/numcodecs/tests/test_checksum32.py
+++ b/numcodecs/tests/test_checksum32.py
@@ -145,6 +145,25 @@ def test_crc32c_checksum():
     assert np.frombuffer(buf, dtype="<u4", offset=(len(buf) - 4))[0] == np.uint32(4218238699)
 
 
+@pytest.mark.skipif(not has_crc32c, reason="Needs `crc32c` installed")
+def test_crc32c_incremental():
+    """Test that CRC32C.checksum supports incremental calculation via value parameter."""
+    # Test incremental checksum calculation (for API compatibility)
+    data1 = np.frombuffer(b"hello", dtype='uint8')
+    data2 = np.frombuffer(b" world", dtype='uint8')
+    full_data = np.frombuffer(b"hello world", dtype='uint8')
+
+    # Calculate checksum in one go
+    checksum_full = CRC32C.checksum(full_data)
+
+    # Calculate incrementally using the value parameter
+    checksum_part1 = CRC32C.checksum(data1, 0)
+    checksum_part2 = CRC32C.checksum(data2, checksum_part1)
+
+    # Both methods should produce the same result
+    assert checksum_full == checksum_part2
+
+
 @pytest.mark.parametrize("codec", codecs)
 def test_err_checksum(codec):
     arr = np.arange(0, 64, dtype="uint8")

From 4497cfa95a2cda160ed2a98766e59b45fc213c95 Mon Sep 17 00:00:00 2001
From: Joseph Hamman <joe@earthmover.io>
Date: Fri, 10 Oct 2025 21:54:19 -0700
Subject: [PATCH 3/3] add crc32c to the test environment for compat with
 existing zarr versions

---
 .pre-commit-config.yaml | 2 +-
 pyproject.toml          | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 723e0a85..49678a44 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -30,4 +30,4 @@ repos:
       hooks:
       -   id: mypy
           args: [--config-file, pyproject.toml]
-          additional_dependencies: [numpy, pytest, google-crc32c, zfpy, 'zarr>=3']
+          additional_dependencies: [numpy, pytest, google-crc32c, crc32c, zfpy, 'zarr>=3']
diff --git a/pyproject.toml b/pyproject.toml
index 68aef3fe..601d3f3c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -61,6 +61,7 @@ test = [
 ]
 test_extras = [
     "importlib_metadata",
+    "crc32c",  # TODO: remove once zarr-python does not depend on crc32c anymore
 ]
 msgpack = [
     "msgpack",