Expose uv_loop_t pointer for integration with other C-extensions (#310)

Co-authored-by: Fantix King <[email protected]>

Author: pranavtbhat

Diff for: setup.py

@@ -34,6 +34,7 @@
     'pycodestyle~=2.7.0',
     'pyOpenSSL~=19.0.0',
     'mypy>=0.800',
+    CYTHON_DEPENDENCY,
 ]
 
 # Dependencies required to build documentation.

Diff for: tests/cython_helper.pyx

@@ -0,0 +1,5 @@
+from cpython.pycapsule cimport PyCapsule_GetPointer
+
+
+def capsule_equals(cap1, cap2):
+    return PyCapsule_GetPointer(cap1, NULL) == PyCapsule_GetPointer(cap2, NULL)

Diff for: tests/test_pointers.py

@@ -0,0 +1,18 @@
+from uvloop import _testbase as tb
+
+
+class Test_UV_Pointers(tb.UVTestCase):
+    def test_get_uv_loop_t_ptr(self):
+        loop = self.new_loop()
+        cap1 = loop.get_uv_loop_t_ptr()
+        cap2 = loop.get_uv_loop_t_ptr()
+        cap3 = self.new_loop().get_uv_loop_t_ptr()
+
+        import pyximport
+
+        pyximport.install()
+
+        from tests import cython_helper
+
+        self.assertTrue(cython_helper.capsule_equals(cap1, cap2))
+        self.assertFalse(cython_helper.capsule_equals(cap1, cap3))

Diff for: uvloop/loop.pyx

@@ -38,6 +38,7 @@ from cpython cimport (
     PyBytes_AsStringAndSize,
     Py_SIZE, PyBytes_AS_STRING, PyBUF_WRITABLE
 )
+from cpython.pycapsule cimport PyCapsule_New
 
 from . import _noop
 
@@ -3180,6 +3181,10 @@ cdef class Loop:
         except Exception as ex:
             self.call_soon_threadsafe(future.set_exception, ex)
 
+    # Expose pointer for integration with other C-extensions
+    def get_uv_loop_t_ptr(self):
+        return PyCapsule_New(<void *>self.uvloop, NULL, NULL)
+
 
 cdef void __loop_alloc_buffer(uv.uv_handle_t* uvhandle,
                               size_t suggested_size,