simplify C to python references

cffi_declarations.c

@@ -755,16 +755,6 @@ const char* uv_err_name(int);
 /* Python */
 const char* PYTHON_UV_CFFI_VERSION;
 
-typedef struct {
-    void* magic;
-    void* object;
-} py_data;
-
-void* py_attach(py_data* data, void* object);
-py_data* py_detach(void* pointer);
-
-
-
 /* Cross-Platform */
 typedef struct {
     uint64_t flowinfo;

cffi_source.c

@@ -15,28 +15,9 @@
 
 #include <uv.h>
 
-const char* PYTHON_UV_CFFI_VERSION = "__version__";
-
 
 /* Python */
-typedef struct {
-    void* magic;
-    void* object;
-} py_data;
-
-void* py_attach(py_data* data, void* object) {
-    data->magic = &py_attach;
-    data->object = object;
-    return (void*) data;
-}
-
-py_data* py_detach(void* pointer) {
-    if (pointer != NULL && ((py_data*) pointer)->magic == &py_attach) {
-        return (py_data*) pointer;
-    }
-    return NULL;
-}
-
+const char* PYTHON_UV_CFFI_VERSION = "__version__";
 
 
 /* Cross-Platform */

uv/handle.py

@@ -118,7 +118,7 @@ class Handle(object):
         uv.Loop
     """
 
-    __slots__ = ['__weakref__', 'loop', 'uv_handle', 'attachment', 'on_closed',
+    __slots__ = ['__weakref__', 'loop', 'uv_handle', '_c_reference', 'on_closed',
                  'closed', 'closing', 'data', 'allocator']
 
     def __init__(self, uv_handle, loop=None):
@@ -134,7 +134,7 @@ def __init__(self, uv_handle, loop=None):
         if self.loop.closed:
             raise error.ClosedLoopError()
         self.uv_handle = ffi.cast('uv_handle_t*', uv_handle)
-        self.attachment = library.attach(self.uv_handle, self)
+        self._c_reference = library.attach(self.uv_handle, self)
         self.on_closed = common.dummy_callback
         """
         Callback which should run after the handle has been closed.

uv/library.py

@@ -17,6 +17,7 @@
 
 import os
 import sys
+
 from collections import namedtuple
 
 from . import __version__
@@ -67,16 +68,54 @@
 Attachment = namedtuple('Attachment', ['c_data', 'c_reference'])
 
 
-def attach(structure, instance):
-    attachment = Attachment(ffi.new('py_data*'), ffi.new_handle(instance))
-    lib.py_attach(attachment.c_data, attachment.c_reference)
-    structure.data = attachment.c_data
-    return attachment
-
-
-def detach(structure):
-    data = lib.py_detach(structure.data)
-    if data: return ffi.from_handle(data.object)
+def attach(c_structure, instance):
+    """
+    Attach a python object to a C data structure's `data` field using
+    :func:`ffi.new_handle`. The returned reference must be stored in
+    order to receive the original object with :func:`detach`.
+
+    :param c_structure:
+        C structure with data field of type `void*`
+    :param instance:
+        python instance to attach
+
+    :type c_structure:
+        ffi.CData
+    :type instance:
+        object
+
+    :return:
+        reference of type `void*` (needs to be stored)
+    :rtype:
+        ffi.CData[void*]
+    """
+    c_reference = ffi.new_handle(instance)
+    c_structure.data = c_reference
+    return c_reference
+
+
+def detach(c_structure):
+    """
+    Detach a python object from a C data structure's data field using
+    :func:`ffi.from_handle`. This might segfault on CPython if the
+    referenced python object or the reference itself has been garbage
+    collected. On PyPy it returns `None` in these cases.
+
+    :param c_structure:
+        C structure with data field of type `void*`
+
+    :return:
+        attached python instance if found
+    :rtype:
+        Optional[object]
+    """
+    if c_structure.data:
+        try:
+            # NOTE: on CPython this might segfault if the pointer is not valid
+            instance = ffi.from_handle(c_structure.data)
+            return instance
+        except SystemError:
+            pass
 
 
 def mutable_c_string(string):

uv/loop.py

@@ -308,7 +308,7 @@ def __init__(self, allocator=None, default=False, buffer_size=2**16):
 
         common.attach_finalizer(self, loop_finalizer, self.uv_loop)
 
-        self.attachment = library.attach(self.uv_loop, self)
+        self._c_reference = library.attach(self.uv_loop, self)
 
         self.allocator = allocator or DefaultAllocator(buffer_size)
 

uv/request.py

@@ -55,11 +55,11 @@ class Request(object):
     :type loop: Loop
     """
 
-    __slots__ = ['uv_request', 'attachment', 'finished', 'loop']
+    __slots__ = ['uv_request', '_c_reference', 'finished', 'loop']
 
     def __init__(self, uv_request, loop=None):
         self.uv_request = ffi.cast('uv_req_t*', uv_request)
-        self.attachment = library.attach(self.uv_request, self)
+        self._c_reference = library.attach(self.uv_request, self)
         self.loop = loop or Loop.get_current()
         """
         Loop where the handle is running on.