os: support blocking functions on Windows

Use the GetNamedPipeHandleState and SetNamedPipeHandleState Win32 API functions to add support for os.get_blocking and os.set_blocking.

Author: RayyanAnsari

Include/internal/pycore_fileutils.h

@@ -160,11 +160,10 @@ PyAPI_FUNC(int) _Py_set_inheritable_async_safe(int fd, int inheritable,
 
 PyAPI_FUNC(int) _Py_dup(int fd);
 
-#ifndef MS_WINDOWS
 PyAPI_FUNC(int) _Py_get_blocking(int fd);
 
 PyAPI_FUNC(int) _Py_set_blocking(int fd, int blocking);
-#else   /* MS_WINDOWS */
+#ifdef MS_WINDOWS
 PyAPI_FUNC(void*) _Py_get_osfhandle_noraise(int fd);
 
 PyAPI_FUNC(void*) _Py_get_osfhandle(int fd);

Lib/test/test_os.py

@@ -4099,6 +4099,7 @@ def test_path_t_converter_and_custom_class(self):
 @unittest.skipUnless(hasattr(os, 'get_blocking'),
                      'needs os.get_blocking() and os.set_blocking()')
 @unittest.skipIf(support.is_emscripten, "Cannot unset blocking flag")
+@unittest.skipIf(sys.platform == 'win32', 'Windows only supports blocking on pipes')
 class BlockingTests(unittest.TestCase):
     def test_blocking(self):
         fd = os.open(__file__, os.O_RDONLY)

Misc/NEWS.d/next/Windows/2023-02-13-18-05-49.gh-issue-101881._TnHzN.rst

@@ -0,0 +1 @@
+Add support for the os.get_blocking() and os.set_blocking() functions on Windows.

Modules/clinic/posixmodule.c.h

@@ -13930,7 +13930,6 @@ os_set_handle_inheritable_impl(PyObject *module, intptr_t handle,
 }
 #endif /* MS_WINDOWS */
 
-#ifndef MS_WINDOWS
 /*[clinic input]
 os.get_blocking -> bool
     fd: int
@@ -13978,7 +13977,6 @@ os_set_blocking_impl(PyObject *module, int fd, int blocking)
         return NULL;
     Py_RETURN_NONE;
 }
-#endif   /* !MS_WINDOWS */
 
 
 /*[clinic input]

Modules/posixmodule.c

@@ -2473,6 +2473,41 @@ _Py_set_blocking(int fd, int blocking)
     return -1;
 }
 #else   /* MS_WINDOWS */
+int
+_Py_get_blocking(int fd)
+{
+    HANDLE handle;
+    DWORD mode;
+
+    handle = _Py_get_osfhandle(fd);
+    if (handle == INVALID_HANDLE_VALUE)
+        return -1;
+
+    if (!GetNamedPipeHandleState(handle, &mode, NULL, NULL, NULL, NULL, 0)) {
+        PyErr_SetFromWindowsErr(0);
+        return -1;
+    }
+    return mode == PIPE_WAIT;
+}
+
+int
+_Py_set_blocking(int fd, int blocking)
+{
+    HANDLE handle;
+    DWORD mode;
+
+    handle = _Py_get_osfhandle(fd);
+    if (handle == INVALID_HANDLE_VALUE)
+        return -1;
+
+    mode = blocking ? PIPE_WAIT : PIPE_NOWAIT;
+    if (!SetNamedPipeHandleState(handle, &mode, NULL, NULL)) {
+        PyErr_SetFromWindowsErr(0);
+        return -1;
+    }
+    return 0;
+}
+
 void*
 _Py_get_osfhandle_noraise(int fd)
 {