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. Regards Antoine. _______________________________________________ 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