On 19 November 2013 09:57, Antoine Pitrou <solip...@pitrou.net> wrote: > On Mon, 18 Nov 2013 16:44:59 -0600 > Tim Peters <tim.pet...@gmail.com> wrote: >> [Tim] >> >> But it has a different kind of advantage: PREFETCH was optional. As >> >> Guido said, it's annoying to bloat the size of small pickles (which >> >> may, although individually small, occur in great numbers) by 8 bytes >> >> each. There's really no point to framing small chunks of data, right? >> >> [Antoine] >> > You can't know how much space the pickle will take until the pickling >> > ends, though, which makes it difficult to decide whether you want to >> > emit a PREFETCH opcode or not. >> >> Ah, of course. Presumably the outgoing pickle stream is first stored >> in some memory buffer, right? If pickling completes before the buffer >> is first flushed, then you know exactly how large the entire pickle >> is. If "it's small" (say, < 100 bytes), don't write out the PREFETCH >> part. Else do. > > Yet another possibility: keep framing but use a variable-length > encoding for the frame size: > > - first byte: bits 7-5: N (= frame size bytes length - 1) > - first byte: bits 4-0: first 5 bits of frame size > - remaning N bytes: remaining bits of frame size > > With this scheme, very small pickles have a one byte overhead; small > ones a two byte overhead; and the max frame size is 2**61 rather than > 2**64, which should still be sufficient. > > And the frame size is read using either one or two read() calls, which > is efficient.
And it's only a minimal change from the current patch. Sounds good to me. Cheers, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com