[Python-Dev] pre-PEP: The Safe Buffer Interface

[Greg Ewing]

> Moreover, if the sensible use cases for locking are few and far
> between, then I'm still inclined to leave it out since you can add the
> locking semantics at a different level.

Are you sure about that? Without the locking, only non-resizable
objects would be able to implement the protocol. So any higher
level locking would have to be implemented on top of the old,
non-safe version. Then you'd have to make sure that all parts
of your application accessed the object through the extra
layer. The "safe" part would be lost.

> Your use of the word *no* is different than mine.  :-) I could
> similarly claim that the segment count puts no burden on
> implementations that don't need it.

I think I may have been replying to something other than what was
said. But what I said is still true -- it imposes no extra burden on
*implementers* of the interface which don't use the extra feature. I
acknowledge that it complicates things slightly for *users* of the
interface, but not as much as the seg count stuff does (there's no
need for any testing or exception raising).

> I believe it will be a no-op in enough places that extension writers
> will do it wrong without even knowing.

Well, there's not much that can be done about extension
writers who fail to read the documentation, or wilfully
ignore it.

> Which exception?  Would you introduce a standard exception that should
> be raised when the user tries to do an operation that currently isn't
> allowed because the buffer is locked?

Maybe. It doesn't matter. The important thing is that the
interpeter does not crash.

> I still believe the locking can be added on top of the simpler
> interface as needed.

But it can't, since as I pointed out above, resizable objects
won't be able to provide the simpler interface!

Greg Ewing, Computer Science Dept, +--------------------------------------+
University of Canterbury,	   | A citizen of NewZealandCorp, a	  |
Christchurch, New Zealand	   | wholly-owned subsidiary of USA Inc.  |
greg@cosc.canterbury.ac.nz	   +--------------------------------------+