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SubjectRe: [PATCH 01/10] Add macros similar to min/max/min_t/max_t.
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On Fri, 2008-03-14 at 09:49 -0700, Randy Dunlap wrote:
> Harvey Harrison wrote:
> > On Fri, 2008-03-14 at 09:34 -0700, Randy Dunlap wrote:
> >> On Thu, 13 Mar 2008 22:18:45 -0700 Harvey Harrison wrote:
> >
> >> Where is some blurb/comment about what "clamp" means/does?
> >> min/max are well understood, but clamp? Is that a shop tool?
> >> I think I have a few out in my garage.
> > Sure, I'll do that..does kernel-doc actually work for macros?
>
> Yes, it does.
>

OK, here's what I've come up with:

/**
* clamp - return a value clamped to a given range with strict typechecking
* @val: current value
* @min: minimum allowable value
* @max: maximum allowable value
*
* This macro does strict typechecking of min/max to make sure they of the
* same type as val. See the unnecessary pointer comparisons.
*/
#define clamp(val, min, max) ({ \
typeof(val) __val = (val); \
typeof(min) __min = (min); \
typeof(max) __max = (max); \
(void) (&__val == &__min); \
(void) (&__val == &__max); \
__val = __val < __min ? __min: __val; \
__val > __max ? __max: __val; })

/**
* clamp_t - return a value clamped to a given range using a given type
* @type: the type of variable to use
* @val: current value
* @min: minimum allowable value
* @max: maximum allowable value
*
* This macro does no typechecking and uses temporary variables of type
* 'type' to make all the comparisons.
*/
#define clamp_t(type, val, min, max) ({ \
type __val = (val); \
type __min = (min); \
type __max = (max); \
__val = __val < __min ? __min: __val; \
__val > __max ? __max: __val; })

/**
* clamp_val - return a value clamped to a given range using val's type
* @val: current value
* @min: minimum allowable value
* @max: maximum allowable value
*
* This macro does no typechecking and uses temporary variables of whatever
* type the input argument 'val' is. This is useful when val is an unisgned
* type and min and max are literals that will otherwise be assigned a signed
* integer type.
*/
#define clamp_val(val, min, max) ({ \
typeof(val) __val = (val); \
typeof(val) __min = (min); \
typeof(val) __max = (max); \
__val = __val < __min ? __min: __val; \
__val > __max ? __max: __val; })

Comments? Please let me know if I got the kerneldoc format right.

Harvey



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