The find_closest() macro can be used to find an element in a sorted array that is closest to an input value.
Signed-off-by: Chris Packham judge.packham@gmail.com ---
include/linux/kernel.h | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 3e71d61074b6..5cd6c9dc8219 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -284,4 +284,28 @@ offsetof(struct structure, member) == (offset), \ "`struct " #structure "` offset for `" #member "` is not " #offset)
+#define __find_closest(x, a, as, op) \ +({ \ + typeof(as) __fc_i, __fc_as = (as) - 1; \ + typeof(x) __fc_x = (x); \ + typeof(*a) const *__fc_a = (a); \ + for (__fc_i = 0; __fc_i < __fc_as; __fc_i++) { \ + if (__fc_x op DIV_ROUND_CLOSEST(__fc_a[__fc_i] + \ + __fc_a[__fc_i + 1], 2)) \ + break; \ + } \ + (__fc_i); \ +}) + +/** + * find_closest - locate the closest element in a sorted array + * @x: The reference value. + * @a: The array in which to look for the closest element. Must be sorted + * in ascending order. + * @as: Size of 'a'. + * + * Returns the index of the element closest to 'x'. + */ +#define find_closest(x, a, as) __find_closest(x, a, as, <=) + #endif