[torchcodec] Add rudimentary support for OSX build

Summary: After these changes I was able to install and run torchcodec on my OSX laptop.

Reviewed By: scotts

Differential Revision: D59065917

fbshipit-source-id: c1025f6c0cbd60de9dc95d7d9cc501b1bf5ad3a6

setup.py

@@ -126,8 +126,17 @@ def copy_extensions_to_source(self):
         This is called by setuptools at the end of .run() during editable installs.
         """
         self.get_finalized_command("build_py")
-
-        for so_file in self._install_prefix.glob("*.so"):
+        extension = ""
+        if sys.platform == "linux":
+            extension = "so"
+        elif sys.platform == "darwin":
+            extension = "dylib"
+        else:
+            raise NotImplementedError(
+                "Platforms other than linux/darwin are not supported yet"
+            )
+
+        for so_file in self._install_prefix.glob(f"*.{extension}"):
             assert "libtorchcodec" in so_file.name
             destination = Path("src/torchcodec/") / so_file.name
             print(f"Copying {so_file} to {destination}")

src/torchcodec/_internally_replaced_utils.py

@@ -1,14 +1,24 @@
 import importlib
 import os
+import sys
 
 
 # Copy pasted from torchvision
 # https://github.com/pytorch/vision/blob/947ae1dc71867f28021d5bc0ff3a19c249236e2a/torchvision/_internally_replaced_utils.py#L25
 def _get_extension_path(lib_name):
     lib_dir = os.path.dirname(__file__)
+    extension_suffixes = []
+    if sys.platform == "linux":
+        extension_suffixes = importlib.machinery.EXTENSION_SUFFIXES
+    elif sys.platform == "darwin":
+        extension_suffixes = importlib.machinery.EXTENSION_SUFFIXES + [".dylib"]
+    else:
+        raise NotImplementedError(
+            "Platforms other than linux/darwin are not supported yet"
+        )
     loader_details = (
         importlib.machinery.ExtensionFileLoader,
-        importlib.machinery.EXTENSION_SUFFIXES,
+        extension_suffixes,
     )
 
     extfinder = importlib.machinery.FileFinder(lib_dir, loader_details)