On Wed, Oct 12, 2016 at 12:17 AM, Serhiy Storchaka <storch...@gmail.com> wrote: > On 12.10.16 09:31, Nathaniel Smith wrote: >> >> But amortized O(1) deletes from the front of bytearray are totally >> different, and more like amortized O(1) appends to list: there are >> important use cases[1] that simply cannot be implemented without some >> feature like this, and putting the implementation inside bytearray is >> straightforward, deterministic, and more efficiently than hacking >> together something on top. Python should just guarantee it, IMO. >> >> -n >> >> [1] My use case is parsing HTTP out of a receive buffer. If deleting >> the first k bytes of an N byte buffer is O(N), then not only does >> parsing becomes O(N^2) in the worst case, but it's the sort of O(N^2) >> that random untrusted network clients can trigger at will to DoS your >> server. > > > Deleting from buffer can be avoided if pass the starting index together with > the buffer. For example: > > def read_line(buf: bytes, start: int) -> (bytes, int): > try: > end = buf.index(b'\r\n', start) > except ValueError: > return b'', start > > return buf[start:end], end+2
It's more complicated than that -- the right algorithm is the one that Antoine implemented in 3.4. But yes, having implemented this by hand, I am aware that it can be implemented by hand :-). My point is that forcing everyone who writes network code in Python to do that is silly, especially given that CPython's apparently been shipping this feature for years. -n -- Nathaniel J. Smith -- https://vorpus.org _______________________________________________ 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
