[issue3489] add rotate{left,right} methods to bytearray
Antoine Pitrou added the comment: I think we can close. issue17100 would have been more useful actually. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue3489 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue3489] add rotate{left,right} methods to bytearray
Serhiy Storchaka added the comment: I think you rather need the inplace shift operation. Or even the move the tail of buffer to the start without filling the remaining. I.e. something like buffer[:size] = buffer[-size:] but without creating immediate bytes object. Now it may be written as: buffer[:size] = memoryview(buffer)[-size:] -- nosy: +serhiy.storchaka ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue3489 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue3489] add rotate{left,right} methods to bytearray
Changes by Terry J. Reedy tjre...@udel.edu: -- resolution: - rejected status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue3489 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue3489] add rotate{left,right} methods to bytearray
Ethan Furman added the comment: Antoine, do you want to pursue, or can we close this? -- nosy: +ethan.furman ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue3489 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue3489] add rotate{left,right} methods to bytearray
Changes by Raymond Hettinger rhettin...@users.sourceforge.net: -- priority: normal - low stage: unit test needed - ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue3489 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue3489] add rotate{left,right} methods to bytearray
Terry J. Reedy tjre...@udel.edu added the comment: Antoine, do you disagree with Raymond or should we close this? In any case, I believe this would delayed by the moratorium. -- nosy: +terry.reedy versions: +Python 3.3 -Python 2.7, Python 3.2 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue3489 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue3489] add rotate{left,right} methods to bytearray
Changes by Daniel Diniz aja...@gmail.com: -- stage: - test needed versions: +Python 3.2 -Python 3.1 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue3489 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue3489] add rotate{left,right} methods to bytearray
Raymond Hettinger rhettin...@users.sourceforge.net added the comment: Am -1 on this. Rotating byte arrays has very few use cases and the ones it does have can typically be met by indexing. -- nosy: +rhettinger ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue3489 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue3489] add rotate{left,right} methods to bytearray
Josiah Carlson [EMAIL PROTECTED] added the comment: Sadly, this isn't quite as easy as it would seem. The O(1) memory overhead version of this requires 2n reads and 2n writes, but does both reads and writes at two memory locations at a time, which may have nontrivial performance implications. The simple version that copies out the small part of the shift into a temporary buffer, doing a memcpy/memmov internally, then copying the small data back is likely to have much better performance (worst-case 1.5n reads and 1.5n writes. Offering this ability in the momoryview object would be very interesting, though I'm not sure that the memoryview object is able to offer a multi-segment buffer interface where the segments are not the same length (this could be hacked by having a single pointer per byte, but at that point we may as well perform a copy). -- nosy: +josiahcarlson ___ Python tracker [EMAIL PROTECTED] http://bugs.python.org/issue3489 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue3489] add rotate{left,right} methods to bytearray
Antoine Pitrou [EMAIL PROTECTED] added the comment:
Hi,
Sadly, this isn't quite as easy as it would seem.
You are right, I was overly optimist when thinking about this.
Offering this ability in the momoryview object would be very
interesting, though I'm not sure that the memoryview object is able to
offer a multi-segment buffer interface where the segments are not the
same length (this could be hacked by having a single pointer per byte,
but at that point we may as well perform a copy).
I'm not sure what you mean, but I think we can just restrict it to the
simple case of a single contiguous buffer.
shift{left,right} could be useful too (and faster).
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[issue3489] add rotate{left,right} methods to bytearray
Josiah Carlson [EMAIL PROTECTED] added the comment: In order for MemoryView to know what bytes it is pointing to in memory, it (generally) keeps a pointer with a length. In order to rotate the data without any copies, you need a pointer and length for each rotation plus the original. For example, the equivalent to a rotate left of 8 characters using slicing is... x[8:] + x[:8]. That is two segments. That's a multi-segment buffer interface. But typical multi-segment buffer interfaces require each segment to be exactly the same length (like numpy), which is not the case with rotations. ___ Python tracker [EMAIL PROTECTED] http://bugs.python.org/issue3489 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue3489] add rotate{left,right} methods to bytearray
Antoine Pitrou [EMAIL PROTECTED] added the comment: Le vendredi 08 août 2008 à 21:44 +, Josiah Carlson a écrit : Josiah Carlson [EMAIL PROTECTED] added the comment: In order for MemoryView to know what bytes it is pointing to in memory, it (generally) keeps a pointer with a length. In order to rotate the data without any copies, you need a pointer and length for each rotation plus the original. For example, the equivalent to a rotate left of 8 characters using slicing is... x[8:] + x[:8]. Hmm, I think it's simpler if the rotate is done in-place rather than returning a new object. Most uses of memoryviews are going to be with APIs requiring a single contiguous segment. (of course for read-only buffers it would raise an error) ___ Python tracker [EMAIL PROTECTED] http://bugs.python.org/issue3489 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue3489] add rotate{left,right} methods to bytearray
New submission from Antoine Pitrou [EMAIL PROTECTED]:
While tweaking the BufferedWriter implementation it came to me that it
would be useful to have rotate_left and rotate_right methods on
bytearray, so as to rotate the array by a number of bytes without any
wasteful memory allocations and copies.
(or, if memoryview is one day implemented it could be a memoryview
method instead...)
--
components: Interpreter Core
messages: 70579
nosy: pitrou
priority: normal
severity: normal
status: open
title: add rotate{left,right} methods to bytearray
type: feature request
versions: Python 2.7, Python 3.1
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