IIRC here is the use case for buffered reader/writer vs. random: a disk file opened for reading and writing uses a random access buffer; but a TCP stream stream, while both writable and readable, should use separate read and write buffers. The reader and writer don't have to worry about reversing the I/O direction.
But maybe I'm missing something about your question? --Guido On Thu, Feb 18, 2010 at 1:59 PM, Pascal Chambon <chambon.pas...@gmail.com> wrote: > Hello, > > As I continue experimenting with advanced streams, I'm currently beginning > an important modification of io's Buffered and Text streams (removal of > locks, adding of methods...), to fit the optimization process of the whole > library. > However, I'm now wondering what the idea is behind the 3 main buffer classes > : Bufferedwriter, Bufferedreader and Bufferedrandom. > > The i/o PEP claimed that the two first ones were for sequential streams > only, and the latter for all kinds of seekable streams; but as it is > implemented, actually the 3 classes can be returned by open() for seekable > files. > > Am I missing some use case in which this distinction would be useful (for > optimizations ?) ? Else, I guess I should just create a RSBufferedStream > class which handles all kinds of situations, raising InsupportedOperation > exceptions whenever needed.... after all, text streams act that way (there > is no TextWriter or TextReader stream), and they seem fine. > > Also, io.open() might return a raw file stream when we set buffering=0. The > problem is that raw file streams are NOT like buffered streams with a buffer > limit of zero : raw streams might fail writing/reading all the data asked, > without raising errors. I agree this case should be rare, but it might be a > gotcha for people wanting direct control of the stream (eg. for locking > purpose), but no silently incomplete read/write operation. > Shouldn't we rather return a "write through" buffered stream in this case > "buffering=0", to cleanly handle partial read/write ops ? > > regards, > Pascal > > PS : if you have 3 minutes, I'd be very interested by your opinion on the > "advanced modes" draft below. > Does it seem intuitive to you ? In particular, shouldn't the "+" and "-" > flags have the opposite meaning ? > http://bytebucket.org/pchambon/python-rock-solid-tools/wiki/rsopen.html > > > > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > http://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > http://mail.python.org/mailman/options/python-dev/guido%40python.org > -- --Guido van Rossum (python.org/~guido) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
