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[Python-Dev] (Licensing question) backport of shutil.copyfile() functionality


On Tue, Mar 12, 2019 at 2:55 PM Giampaolo Rodola' <g.rodola at gmail.com>
wrote:

>
>
> On Tue, Mar 12, 2019 at 3:01 AM Glenn Linderman <v+python at g.nevcal.com>
> wrote:
>
>> On 3/11/2019 4:35 PM, Giampaolo Rodola' wrote:
>>
>> Hello,
>> some time ago I contributed a couple of patches to speedup shutil.copy*()
>> functions:
>> https://bugs.python.org/issue33671
>> https://bugs.python.org/issue33695
>> I would like to backport both functionalities so that they can be used on
>> Python 2.7 and <3.8 and put it on PYPI. In order to do so I will basically
>> have to copy some parts of shutil module (copytree() function + the
>> unit-tests I added in BPO-33671 and a couple of other things). Are there
>> constraints regarding this in terms of license? Am I supposed to use GPL?
>> (I was thinking about using MIT)
>>
>> Note: in this package called "zerocopy" I will probably want to expose
>> other functionalities such as tee(), splice() and CopyFileEx and
>> TransmitFile on Windows, so it's probably gonna be half a backport and half
>> a brand new project.
>>
>> Thanks.
>>
>>
>> Thanks for the contributions. I don't know about the licensing.
>>
>> I wonder if you should make two packages, though... one just exactly a
>> backport of the shutil speedups, and the second containing the new
>> functionalities.
>>
>
> That was my initial thought as well (a "backports.shutil_copy" module
> targeting copy* functions only), but (especially after playing with this
> today) I think I have something a bit more ambitious in mind. I'm currently
> experimenting with different things which could be baked in a third-party
> lib and possibly contributed back to Python later on:
>

If you might want some of this contributed back to Python later on, you
should not use the GPL.

1) on OSX we could use f/copyfile() syscall to copy file attrs/metadata;
> that may be useful to speedup shutil.copystat() and shutil.copymode()
> 2) copytree() on OSX could take advantage of f/copyfile() +
> COPYFILE_RECURSIVE (which is probably too platform-specific for inclusion)
> 3) on Linux we could use copy_file_range() as a replacement for
> os.sendfile() in shutil.copyfile() (it's supposed to be faster)
> 4) on Linux ioctl() + FICLONE could be used to implement CoW (copy on
> write) instantaneous copies, and could be added as shutil.cow_copyfile()
> (haven't look into Windows yet)
> 5) I was thinking about backporting socket.socket.sendfile() as well,
> which uses os.sendfile() on POSIX but not TransmitFile on Windows (asyncio
> does though)
> 6)  another idea (but I'm not sure if it's possible, as I still have to
> dig into that) is a new socket recvfile() function boosted up by tee() /
> splice() on Linux, which maybe could be contributed back as
> socket.socket.recvfile()
>
> --
> Giampaolo - http://grodola.blogspot.com
>
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