Avoid memory copy in obstore write

src/zarr/core/buffer/core.py

@@ -251,6 +251,19 @@
         """
         ...
 
+    def as_bytes_like(self) -> BytesLike:
+        """Returns the buffer as a bytes-like object.
+
+        Notes
+        -----
+        Might have to copy data, since the implementation uses `.as_numpy_array()`.
+
+        Returns
+        -------
+            A bytes-like object that implements the Python buffer protocol
+        """
+        return memoryview(self.as_numpy_array().view(np.uint8))  # type: ignore[arg-type]
+
     def to_bytes(self) -> bytes:
         """Returns the buffer as `bytes` (host memory).
 

src/zarr/storage/_obstore.py

@@ -145,15 +145,15 @@
 
         self._check_writable()
 
-        buf = value.to_bytes()
+        buf = value.as_bytes_like()
         await obs.put_async(self.store, key, buf)
 
     async def set_if_not_exists(self, key: str, value: Buffer) -> None:
         # docstring inherited
         import obstore as obs
 
         self._check_writable()
-        buf = value.to_bytes()
+        buf = value.as_bytes_like()
         with contextlib.suppress(obs.exceptions.AlreadyExistsError):
             await obs.put_async(self.store, key, buf, mode="create")