Determine if a value lies within a range more efficiently (subtraction +
comparison vs two comparisons and an AND). It also has useful (under
some circumstances) behaviour if the range exceeds the maximum value of
the type.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
include/linux/minmax.h | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/include/linux/minmax.h b/include/linux/minmax.h
index 396df1121bff..028069a1f7ef 100644
--- a/include/linux/minmax.h
+++ b/include/linux/minmax.h
@@ -158,6 +158,32 @@
*/
#define clamp_val(val, lo, hi) clamp_t(typeof(val), val, lo, hi)
+static inline bool in_range64(u64 val, u64 start, u64 len)
+{
+ return (val - start) < len;
+}
+
+static inline bool in_range32(u32 val, u32 start, u32 len)
+{
+ return (val - start) < len;
+}
+
+/**
+ * in_range - Determine if a value lies within a range.
+ * @val: Value to test.
+ * @start: First value in range.
+ * @len: Number of values in range.
+ *
+ * This is more efficient than "if (start <= val && val < (start + len))".
+ * It also gives a different answer if @start + @len overflows the size of
+ * the type by a sufficient amount to encompass @val. Decide for yourself
+ * which behaviour you want, or prove that start + len never overflow.
+ * Do not blindly replace one form with the other.
+ */
+#define in_range(val, start, len) \
+ sizeof(start) <= sizeof(u32) ? in_range32(val, start, len) : \
+ in_range64(val, start, len)
+
/**
* swap - swap values of @a and @b
* @a: first value
--
2.39.2
