[issue5888] mmap ehancement - resize with sequence notation
Changes by Ned Deily n...@acm.org: -- nosy: +neologix ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue5888 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue5888] mmap ehancement - resize with sequence notation
Mark Lawrence added the comment: @Brian this will go nowhere without a patch covering code, tests and documentation, are you interested in providing one? -- nosy: +BreamoreBoy versions: +Python 2.7, Python 3.5 -Python 3.4 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue5888 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue5888] mmap ehancement - resize with sequence notation
Josh Rosenberg added the comment: I see a few issues with this: 1. Changing the default behavior is a compatibility issue. I've written code that depends on exceptions being raised if slice assignment sizes don't match. 2. The performance cost is high; changing from rewriting in place to shrinking or expanding slice assignment requires (in different orders for shrink/expand) truncating the file to the correct length, memcpy-ing data proportionate to the data after the end of the slice (not proportionate to the slice size) and probably remapping the file (which causes problems if someone has a buffer attached to the existing mapping). At least with non-file backed sequences, when we do work like this it's all in memory and typically smallish; with a file, most of it has to be read from and written to disk, and I'd assume the data being worked with is largish (if it's reliably small, the advantages of mmap-ing are small). 3. Behavior in cases where the whole file isn't mapped is hard to intuit or define reasonably. If I map the first 1024 bytes of a 2 GB file, and I add 20 bytes in the middle of the block, what happens? Does data from the unmapped portions get moved? Overwritten? What about removing 20 bytes from the middle of the block? Do we write 0s, or copy down the data that appears after? And remember, for all but the shrink and write 0s option, we're moving or modifying data the user explicitly didn't mmap. -- nosy: +josh.rosenberg ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue5888 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue5888] mmap ehancement - resize with sequence notation
Changes by Ezio Melotti ezio.melo...@gmail.com: -- versions: +Python 3.4 -Python 3.2 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue5888 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue5888] mmap ehancement - resize with sequence notation
Changes by Terry J. Reedy tjre...@udel.edu: -- components: +Library (Lib) stage: - unit test needed versions: +Python 3.2 -Python 2.6 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue5888 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue5888] mmap ehancement - resize with sequence notation
New submission from Brian Mearns bmea...@ieee.org: I thought it would be nice if mmaps could generally look a little more like sequences. Specifically, being able to resize+write using square-bracket notation as with lists: x = [1,2,3,4,5] x [1, 2, 3, 4, 5] x[2:2] = [6,7,8,9] x [1, 2, 6, 7, 8, 9, 3, 4, 5] If that could be done when x is an mmap.mmap, it'd be great. alternatively, if mmap had an insert or an extend method that work like with lists, the same behavior could be achieved without relying on mmap specific method-names. -- messages: 86849 nosy: bmearns severity: normal status: open title: mmap ehancement - resize with sequence notation type: feature request versions: Python 2.6 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue5888 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
