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Diffstat (limited to 'hash/log2.go')
-rw-r--r--hash/log2.go15
1 files changed, 15 insertions, 0 deletions
diff --git a/hash/log2.go b/hash/log2.go
new file mode 100644
index 0000000..8ba79df
--- /dev/null
+++ b/hash/log2.go
@@ -0,0 +1,15 @@
+package hash
+
+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]
+}