[Python-3000] patch: bytes object PyBUF_LOCKDATA read-only and immutable support (original) (raw)

Guido van Rossum guido at python.org
Tue Sep 11 05:58:17 CEST 2007

I'd like to see Travis's response to this. It's setting a precedent regarding locking objects in read-only mode; I haven't found other examples of objects using LOCKDATA (the only mentions of it seem to be rejecting it :). I keep getting confused by the two separate lock counts (and I think in this version the comment is inconsistent with the code). So I'm hoping Travis has a particular way in mind of handling LOCKDATA that can be used as a template.

Travis?

--Guido

On 9/8/07, Gregory P. Smith <greg at krypto.org> wrote:

A new version is attached; cleaned up and simplified based on your original comments.

On 8/29/07, Guido van Rossum < guido at python.org> wrote: > That's a huge patch to land so close before a release. I'm not sure I > like the immutability API -- it won't be useful unless we add a hash > method, and then we have all sorts of difficulties again -- the > distinction between a hashable and an unhashable object should be made > by type, not by value (tuples containing unhashable values > notwithstanding). ok i've removed the immutable support in the most recent patch. i still think it -might- be useful but isn't required and you're right that it could open a can of worms if people think it should also mean hashable. immutable bytes may be best implemented as a subclass if its ever wanted. > I don't understand the comment about using PyBUFWRITABLE in > getbuffer() -- this is only used for data we're reading and I don't > think the GIL is even released while we're reading such things. that appears to be correct. the comment was wrong. fixed. -gps

> If you think it's important to get this in the 3.0a1 release, we > should pair-program on it ASAP, preferable tomorrow morning. > Otherwise, let's do a review next week. > > --Guido > > On 8/29/07, Gregory P. Smith < greg at krypto.org> wrote: > > Attached is what I've come up with so far. Only a single field is > > added to the PyBytesObject struct. This adds support to the bytes > > object for PyBUFLOCKDATA buffer API operation. bytes objects can be > > marked temporarily read-only for use while the buffer api has handed > > them off to something which may run without the GIL (think IO). Any > > attempt to modify them during that time will raise an exception as I > > believe Martin suggested earlier. > > > > As an added bonus because its been discussed here, support for setting > > a bytes object immutable has been added since its pretty trivial once > > the read only export support was in place. Thats not required but was > > trivial to include. > > > > I'd appreciate any feedback. > > > > My TODO list for this patch: > > > > 0. Get feedback and make adjustments as necessary. > > > > 1. Deciding between PyBUFSIMPLE and PyBUFWRITEABLE for the internal > > uses of the getbuffer() function. bytesobject.c contains both readonly > > and read-write uses of the buffers, i'll add boolean parameter for > > that. > > > > 2. More testing: a few tests in the test suite fail after this but the > > number was low and I haven't had time to look at why or what the > > failures were. > > > > 3. Exporting methods suggested in the TODO at the top of the file. > > > > 4. Unit tests for all of the functionality this adds. > > > > NOTE: after these changes I had to make clean and rm -rf build before > > things would not segfault on import. I suspect some things (modules?) > > were not properly recompiled after the bytesobject.h struct change > > otherwise. > > > > -gps > > > > _> > ________________________ > > Python-3000 mailing list > > Python-3000 at python.org > > http://mail.python.org/mailman/listinfo/python-3000 > > Unsubscribe: http://mail.python.org/mailman/options/python-3000/guido%40python.org > > > > > > > > > -- > --Guido van Rossum (home page: http://www.python.org/~guido/) >

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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