Messages in this thread | | | Subject | Re: [RFC PATCH 01/20] Create generic alignment API (v8) | From | Steven Rostedt <> | Date | Tue, 17 Aug 2010 21:25:26 -0400 |
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On Tue, 2010-08-17 at 19:16 -0400, Mathieu Desnoyers wrote:
> +/* > + * Align pointer on natural object alignment. Object size must be power of two. > + */
Hmm, I wonder if we should add a compiler bug here too.
extern void __bug_obj_not_power_of_two(void);
({ if ((sizeof(*obj) - 1) & sizeof(*obj)) __bug_obj_not_power_of_two(); PTR_ALIGN((obj), __alignof__(*(obj))); })
> +#define object_align(obj) PTR_ALIGN((obj), __alignof__(*(obj))) > +#define object_align_floor(obj) PTR_ALIGN_FLOOR((obj), __alignof__(*(obj))) > + > +/** > + * offset_align - Calculate the offset needed to align an object on its natural > + * alignment towards higher addresses. > + * @align_drift: object offset from an "alignment"-aligned address. > + * @alignment: natural object alignment. Must be non-zero, power of 2. > + * > + * Returns the offset that must be added to align towards higher > + * addresses. > + */ > +static inline size_t offset_align(size_t align_drift, size_t alignment) > +{ > + return (alignment - align_drift) & (alignment - 1); > +} > + > +/** > + * offset_align_floor - Calculate the offset needed to align an object > + * on its natural alignment towards lower addresses. > + * @align_drift: object offset from an "alignment"-aligned address. > + * @alignment: natural object alignment. Must be non-zero, power of 2. > + * > + * Returns the offset that must be substracted to align towards lower addresses. > + */ > +static inline size_t offset_align_floor(size_t align_drift, size_t alignment) > +{ > + return (align_drift - alignment) & (alignment - 1); > +}
I take it that theses functions can have variables passed to it for alignment, thus a check wont help. Although, we could add a test for the constant case.
-- Steve
> +
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