help: is there any way to use integer 64 type in protocol?

[Wang, Quanxian]

From: Jason Ekstrand [mailto:jason at jlekstrand.net]
Sent: Monday, April 21, 2014 10:29 PM
To: Wang, Quanxian
Cc: Pekka Paalanen; wayland-devel at lists.freedesktop.org
Subject: Re: help: is there any way to use integer 64 type in protocol?



On Sun, Apr 20, 2014 at 8:36 PM, Wang, Quanxian <quanxian.wang at intel.com<mailto:quanxian.wang at intel.com>> wrote:


From: Jason Ekstrand [mailto:jason at jlekstrand.net<mailto:jason at jlekstrand.net>]
Sent: Monday, April 21, 2014 6:32 AM
To: Pekka Paalanen
Cc: Wang, Quanxian; wayland-devel at lists.freedesktop.org<mailto:wayland-devel at lists.freedesktop.org>
Subject: Re: help: is there any way to use integer 64 type in protocol?



On Sun, Apr 20, 2014 at 1:17 PM, Pekka Paalanen <ppaalanen at gmail.com<mailto:ppaalanen at gmail.com>> wrote:
On Sun, 20 Apr 2014 11:10:15 +0000
"Wang, Quanxian" <quanxian.wang at intel.com<mailto:quanxian.wang at intel.com>> wrote:

> Hi,
>
> Is there any way to use type of integer 64bit in protocol?
No. You will have to use two 32-bit arguments, or propose a patch
to add 64-bit types in a completely backwards-compatible way. I am
not sure what the latter option would entail.

Adding 64-bit types wouldn't be too hard.  It would involve adding a int64_t an uint64_t types to wl_argument (I'd call them U and I personally) and adding code throughout libwayland to parse them.  In terms of backwards compatibility, it should be fine as long as you make it 100% clear that your new protocol extension uses the new 64bit types and therefore requires the newer libwayland version.
The other option is that you could do what Pekka did in the presentation extension and split it into two 32-bit parts.  What do you want to represent that needs a 64-bit type?
[Wang, Quanxian] 32 is too short. Currently I use 32bit in Weston randr, it could only stand for 16 type of operations (every type use 2 bits, however 12 of 16 have been used.). It will be fine to use 64 bit or more for future extension. I will try to add a patch for that. Thanks for your comment.
As Thiago pointed out, we can't actually add that at this point (sorry, I forgot about the 32-bit machine issue).  Also, if you're using a bitfield and you think there's a reasonable chance of 32 bits being too small, then there is probably also a reasonable chance of 64 bits being too small.  It might be a good idea to consider other ways of representing it.  What exactly are you representing in this bitfield?
[Wang, Quanxian] That is fine. Every 2bit field will stand for the results for every operation(4 type of results). So if only 32bit, there is only 16 type of operation could be supported. 64bit will be enough.
Currently I follow suggestion of Pq to use two 32bit parameters stands for 64 bit results. It works for me now. I will not change more. Thanks for your suggestion.
Thanks,
--Jason Ekstrand

Thanks,
--Jason Ekstrand


The presentation extension could make use of a 64-bit type, too.


Thanks,
pq
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