Pickling ctypes pointer/array

Hi all,

this  question was triggered by the suggestion of Eryk in
http://bugs.python.org/issue27274. Currently my way to go in order to
pickle/unpickle the underlying array of a pointer is:

ptr --cast--> array --copy--> bytes --dump--> pickle
pickle --load--> bytes --(from_buffer_)copy --> array --cast--> ptr

Eryk suggested a more concise way of achieving the same:

ptr --string_at --> bytes --dump--> pickle
pickle --load--> bytes --> create_string_buffer --> ptr

(where I'm taking create_string_buffer as a kind of inverse of string_at).

But this still makes a couple of copies. There are at least two obstacles
on the way to pickling without copies:

1. Pickle is unable to serialize memoryviews.
2. It's not desirable to expose a pointer to the underlying memory of a
bytes object, since bytes are supposed to be immutable.

Now, what about bytearrays? If the underlying buffer of ctypes objects were
get/settable as (views to) bytearrays no immutability constraint would be
violated and we could move between python and c worlds without copying.

Is something like that already possible? If not, is there an essential
limitation preventing its implementation?

Thank you in advance
--
Carlos

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