[Python-Dev] PEP 298 (original) (raw)

Martin v. L�wis martin@v.loewis.de
12 Dec 2002 21🔞52 +0100

Thomas Heller <theller@python.net> writes:

> - How will string objects implement that interface? In particular, > what prevents the refcount of the string dropping to zero? >

It is required to unlock the buffer again after you don't need it any longer. You do this by calling the releaselockedbuffer() function with the pointer to the original python object. So the object haas to keep alive.

This is flawed. According to the PEP, an object which has acquirelockedbuffer called will live forever:

Retrieving a buffer from an object puts this object in a locked

state during which the buffer may not be freed, resized, or

reallocated.

But now you are saying that the object can be released even in locked state.

> Using /dev/poll on Solaris requires a way to create a struct whose > address you know.

Hm, the usual hacky way is to use an array object and call bufferinfo() on it.

I see. I didn't know that. However, having to copy a string to an array to obtain its address is not obvious; putting it into the buffer objects seems more logical - especially if the buffer claims to be locked.

That may be, but the PEP only describes the interface. Extensions may implement a 'locked buffer object', or whatever, and expose the address to Python. Dangerous, though, because then you can separate the python oobject pointer and the buffer pointer.

If it is just the interface, I'm -1. You don't need a PEP to define an interface in Python - just establish an interface in the types you care about. If you really mean to implement it primarily for some type of yours, just do so (it' can't be exactly this interface, but you can have the same operations, just in a different place).

Regards, Martin