How to deal with a block of memory when pickling?

Good afternoon!

I guess that the following has a standard solution, but i don't know it.

Using cython (hope that the pyrex list also answers cython questions), i 
cdefined some class MTX (it is a wrapper for C-MeatAxe matrices). One of 
the attributes is a pointer p to a block of memory that defines the 
coefficients of the matrix.

Now i want to pickle it. One obvious way is to get a list of matrix 
entries and work with it. But this is too slow. Is there a more direct way 
to handle the block of memory p is pointing at?

I tried to make a type cast of p to char* and to read this as a string.
In some cases it worked, and going the way back (string -> char*)
reconstructed the memory block p was pointing at.
 However, sometimes apparently it was not clear to python how long the 
string is supposed to be; so i got an empty string, and the reconstruction 
failed.

What can i do? 

Cheers
	Simon