bpo-44582: Accelerate mimetypes.init on Windows with a native accelerator (GH-27059)

2 files changed, 42 insertions, 6 deletions

diff --git a/Lib/mimetypes.py b/Lib/mimetypes.py
index 4cd9404..b3d70e4 100644
--- a/Lib/mimetypes.py
+++ b/Lib/mimetypes.py
@@ -27,6 +27,12 @@ import os
 import sys
 import posixpath
 import urllib.parse
+
+try:
+    from _winapi import _mimetypes_read_windows_registry
+except ImportError:
+    _mimetypes_read_windows_registry = None
+
 try:
     import winreg as _winreg
 except ImportError:
@@ -237,10 +243,21 @@ class MimeTypes:
         types.
         """
 
-        # Windows only
-        if not _winreg:
+        if not _mimetypes_read_windows_registry and not _winreg:
             return
 
+        add_type = self.add_type
+        if strict:
+            add_type = lambda type, ext: self.add_type(type, ext, True)
+
+        # Accelerated function if it is available
+        if _mimetypes_read_windows_registry:
+            _mimetypes_read_windows_registry(add_type)
+        elif _winreg:
+            self._read_windows_registry(add_type)
+
+    @classmethod
+    def _read_windows_registry(cls, add_type):
         def enum_types(mimedb):
             i = 0
             while True:
@@ -265,7 +282,7 @@ class MimeTypes:
                             subkey, 'Content Type')
                         if datatype != _winreg.REG_SZ:
                             continue
-                        self.add_type(mimetype, subkeyname, strict)
+                        add_type(mimetype, subkeyname)
                 except OSError:
                     continue
 
@@ -349,8 +366,8 @@ def init(files=None):
 
     if files is None or _db is None:
         db = MimeTypes()
-        if _winreg:
-            db.read_windows_registry()
+        # Quick return if not supported
+        db.read_windows_registry()
 
         if files is None:
             files = knownfiles
diff --git a/Lib/test/test_mimetypes.py b/Lib/test/test_mimetypes.py
index f5c040a..fb9cb04 100644
--- a/Lib/test/test_mimetypes.py
+++ b/Lib/test/test_mimetypes.py
@@ -9,6 +9,11 @@ from test import support
 from test.support import os_helper
 from platform import win32_edition
 
+try:
+    import _winapi
+except ImportError:
+    _winapi = None
+
 
 def setUpModule():
     global knownfiles
@@ -235,6 +240,21 @@ class Win32MimeTypesTestCase(unittest.TestCase):
         eq(self.db.guess_type("image.jpg"), ("image/jpeg", None))
         eq(self.db.guess_type("image.png"), ("image/png", None))
 
+    @unittest.skipIf(not hasattr(_winapi, "_mimetypes_read_windows_registry"),
+                     "read_windows_registry accelerator unavailable")
+    def test_registry_accelerator(self):
+        from_accel = {}
+        from_reg = {}
+        _winapi._mimetypes_read_windows_registry(
+            lambda v, k: from_accel.setdefault(k, set()).add(v)
+        )
+        mimetypes.MimeTypes._read_windows_registry(
+            lambda v, k: from_reg.setdefault(k, set()).add(v)
+        )
+        self.assertEqual(list(from_reg), list(from_accel))
+        for k in from_reg:
+            self.assertEqual(from_reg[k], from_accel[k])
+
 
 class MiscTestCase(unittest.TestCase):
     def test__all__(self):
@@ -288,6 +308,5 @@ class MimetypesCliTestCase(unittest.TestCase):
         type_info = self.mimetypes_cmd("foo.pic")
         eq(type_info, "I don't know anything about type foo.pic")
 
-
 if __name__ == "__main__":
     unittest.main()