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-rw-r--r--internal/hash/log2.go18
1 files changed, 12 insertions, 6 deletions
diff --git a/internal/hash/log2.go b/internal/hash/log2.go
index 5e30f17..8ba79df 100644
--- a/internal/hash/log2.go
+++ b/internal/hash/log2.go
@@ -1,9 +1,15 @@
package hash
-func log2(num uint32) uint32 {
- var i uint32
- for limit := uint32(1); limit < num; limit <<= 1 {
- i++
- }
- return i
+var tab32 = [32]uint32{
+ 0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30,
+ 8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31,
+}
+
+func log2(value uint32) uint32 {
+ value |= value >> 1
+ value |= value >> 2
+ value |= value >> 4
+ value |= value >> 8
+ value |= value >> 16
+ return tab32[(value*0x07c4acdd)>>27]
}