[Python-Dev] Accepting PEP 3154 for 3.4? (original) (raw)

Tim Peters tim.peters at gmail.com
Tue Nov 19 20:22:52 CET 2013

[Guido]

So using an opcode for framing is out? (Sorry, I've lost track of the back-and-forth.)

It was never in ;-) I'd prefer one, but not enough to try to block the PEP. As is, framing is done at a "lower level" than opcode decoding. I fear this is brittle, for all the usual "explicit is better than implicit" kinds of reasons. The only way now to know that you're looking at a frame size is to keep a running count of bytes processed and realize you've reached a byte offset where a frame size "is expected".

With an opcode, framing could also be optional (whenever desired), because frame sizes would be explicitly marked in the byte stream Then the framing overhead for small pickles could drop to 0 bytes (instead of the current 8, or 1 thru 9 under various other schemes).

Ideal would be an explicit framing opcode combined with variable-length size encoding. That would never require more bytes than the current scheme, and 'almost always" require fewer. But even I don't think it's of much value to chop a few bytes off every 64KB of pickle ;-)

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