Re: [Libguestfs] [libnbd PATCH v2 5/8] python: Make py_aio_buffer a private struct

Instead of having methods.c poking into the internals of a struct that we defined, have it use PyMemoryView* and Py_buffer*; this separation makes it easier to separate how we store the persistent data (for now, in a PyCapsule) from how we access the data. Eventually, the use of PyMemoryView* will make it easier for future patches to get rid of some layers of copying. nbd_internal_py_init_aio_buffer() is new; for now it doesn't fail, but it can in a future patch. For now, we still have to hang on to a python reference to the PyCapsule object holding our malloc'd C pointer, and since the MemoryView we just created is not backed by a Python object, we must ensure we don't leak it to Python code. But this will change in an upcoming patch.

@@ -477,13 +481,8 @@ let (* Second pass, and call the underlying C function. *) List.iter ( function - | BytesPersistIn (n, _) -> - pr " if (!%s_buf->initialized) {\n" n; - pr " memset (%s_buf->data, 0, %s_buf->len);\n" n n; - pr " %s_buf->initialized = true;\n" n; - pr " }\n" | BytesPersistOut (n, _) -> - pr " %s_buf->initialized = true;\n" n + pr " if (nbd_internal_py_init_aio_buffer (%s) < 0) goto out;\n" n