[vlc-devel] [PATCH 1/3] vlc_common.h: add helpers to get the upper rounded value of integer divisions

[Steve Lhomme]

On Fri, Mar 17, 2017 at 10:14 AM, Steve Lhomme <robux4 at gmail.com> wrote:
> On Fri, Mar 17, 2017 at 9:46 AM, Rémi Denis-Courmont <remi at remlab.net> wrote:
>> On March 17, 2017 4:36:08 PM GMT+08:00, Steve Lhomme <robux4 at videolabs.io> wrote:
>>>---
>>> include/vlc_common.h | 5 +++++
>>> 1 file changed, 5 insertions(+)
>>>
>>>diff --git a/include/vlc_common.h b/include/vlc_common.h
>>>index 6a75753dbf..b72dbfe689 100644
>>>--- a/include/vlc_common.h
>>>+++ b/include/vlc_common.h
>>>@@ -507,6 +507,11 @@ struct vlc_common_members
>>> /* clip v in [min, max] */
>>> #define VLC_CLIP(v, min, max)    __MIN(__MAX((v), (min)), (max))
>>>
>>>+/* upper rounded value of the integer division */
>>>+#define VLC_UPPER_DIV(v, div)     (((v) + (div) - 1) / (div))
>>>+/* upper modulo value of the integer */
>>>+#define VLC_UPPER_MODULO(v, mod)  (VLC_UPPER_DIV(v, mod) * mod)
>>>+
>>> VLC_USED
>>> static inline int64_t GCD ( int64_t a, int64_t b )
>>> {
>>>--
>>>2.11.1
>>>
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>>
>> I don't like expansion-unsafe functional macros, TBH. They've bitten too many asses too many times, so to speak.
>
> Reading on the subject, it seems the position of the parenthesis
> matters (!). Would this be ok ?
> #define VLC_UPPER_MODULO(v, mod)  ((mod) * VLC_UPPER_DIV(v, mod))
>
> or probably better
>
> #define VLC_UPPER_MODULO(v, mod)  ((v) + (v)%(mod))

Or not, it would be 1 minus the modulo, but only when it's not 0...

>> --
>> Rémi Denis-Courmont
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