[Python-3000] patch: bytes object PyBUF_LOCKDATA read-only and immutable support

[Greg Ewing]

Travis E. Oliphant wrote:
> I would want to encourage people not to use the LOCK_FOR_READ unless 
> there is an important benefit or need to use it.

If you mean that LOCK_FOR_READ would unilaterally deny
anyone else read access, my proposal avoids this by not
having such a mode at all. So you can always get read
access if you really want it.

But I expect that most of the time you'll at least want
to make sure nobody is writing while you're trying to
read. In my terminology you spell that READ | EXCLUDE_WRITE.

> Let me think about adding a function for read-write locking that is 
> separate from getting a view (which implements memory-location 
> locking).

I'm not sure it needs to be a separate function, just
a clearly separated set of options in the flags.

Remember that clients are only supposed to be holding
a buffer for as short a time as possible. It's most
likely that the same read/write locking options are
going to apply for the whole duration of a buffer
operation, I think.

-- 
Greg Ewing, Computer Science Dept, +--------------------------------------+
University of Canterbury,	   | Carpe post meridiem!          	  |
Christchurch, New Zealand	   | (I'm not a morning person.)          |
greg.ewing at canterbury.ac.nz	   +--------------------------------------+