Guido van Rossum wrote:
« Q: Do we want to mandate in the specification that switching between reading
and writing on a read-write object implies a .flush()? Or is that an
implementation convenience that users should not rely on? »
Is it ok if I assume that the answer is "it is an implementation convenience
that users should not rely on"? The reason is that I'm overhauling
BufferedRandom objects to use a single shared buffer, so as to optimize
interleaved reads and writes.
I think it's fine if the flush to the file is optional, as long as
this is clearly documented. However, the semantics of interleaving
reads and writes, with and without seek calls in between, should be
well-defined and correct/useful, so that it behaves the same
regardless of the buffer size.
I don't know how much of the stdio will be wrapped or replaced, but,
FWIW, the C89 Standard, as described by Plauger & Brodie, requires a
position-setting operation between writes and reads: one of fflush,
fseek, fsetpos, or rewind. Same for reads and writes unless the read
set EOF.
Ditto for the flush call currently implied by a seek -- if you can
satisfy the seek by moving where you are in the buffer without
flushing, that's fine IMO, but it should be well documented.
It should also be documented that a flush still *may* occur, of course.
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