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[Python-Dev] Accepting PEP 3154 for 3.4?

Antoine Pitrou solipsis at pitrou.net
Wed Nov 20 01:10:50 CET 2013 
On Wed, 20 Nov 2013 00:56:13 +0100
"Martin v. Löwis" <martin at v.loewis.de> wrote:
> AFAICT, the real driving force is the desire to not read-ahead
> more than the pickle is long. This is what complicates the code.
> The easiest (and most space-efficient) solution to that problem
> would be to prefix the entire pickle with a data size field
> (possibly in a variable-length representation), i.e. to make a
> single frame.

Pickling then becomes very problematic: you have to keep the entire
pickle in memory until the end, when you finally can write the size at
the beginning of the pickle.

> If that was done, I would guess that Tim's concerns about brittleness
> would go away (as you couldn't have a length field in the middle of
> data). IMO, the PEP has nearly the same flaw as the HTTP chunked
> transfer, which also puts length fields in the middle of the payload
> (except that HTTP makes it worse by making them optional).

Tim's concern is easily addressed with a FRAME opcode, without
changing the overall scheme (as he lately proposed).

Regards

Antoine.
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