Re: [RFC/PATCH] packfile: use extra variable to clarify code in use_pack()
- Date: Tue, 12 Mar 2019 16:26:06 -0400
- From: Jeff King <peff@xxxxxxxx>
- Subject: Re: [RFC/PATCH] packfile: use extra variable to clarify code in use_pack()
On Tue, Mar 12, 2019 at 05:39:13PM +0000, Ramsay Jones wrote:
> On 12/03/2019 16:55, Ramsay Jones wrote:
> > From: Jeff King <peff@xxxxxxxx>
> > Signed-off-by: Ramsay Jones <ramsay@xxxxxxxxxxxxxxxxxxxx>
Could definitely use a commit message. I think it's something like:
We use the "offset" variable for two purposes. It's the offset into
the packfile that the caller provides us (which is rightly an off_t,
since we might have a packfile much larger than memory). But later we
also use it as the offset within a given mmap'd window, and that
window cannot be larger than a size_t.
For the second use, the fact that we have an off_t leads to some
confusion when we assign it to the "left" variable, is a size_t. It is
in fact correct (because our earlier "offset -= win->offset" means we
must be within the pack window), but using a separate variable of the
right type makes that much more obvious.
You'll note that I snuck in the assumption that "left" is a size_t,
which as you noted is not quite valid yet. :)
> Heh, of course I should have tried applying on top of today's
> codebase before sending it out! :(
> Having just done so, it quickly showed that this patch assumes
> that the 'left' parameter to use_pack() has been changed from
> an 'unsigned long *' to an 'size_t *' as part of the series
> that was being discussed in the above link.
Yep. Until then, I do not think there is much point (and in fact I'd
suspect this code behaves incorrectly on Windows, where "unsigned long"
is too short; hopefully they clamp pack windows to 4GB by default
there, which would work around it).
But I would be very happy if you wanted to resurrect the "left" patch
and then do this on top. :)