File: clz.go

package info (click to toggle)
golang-github-dgryski-go-bits 0.0~git20180112.bd8a69a-1
  • links: PTS, VCS
  • area: main
  • in suites: buster
  • size: 104 kB
  • sloc: asm: 24; makefile: 2
file content (37 lines) | stat: -rw-r--r-- 472 bytes parent folder | download | duplicates (2) 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
 
// +build gccgo !amd64 appengine

package bits

// Clz counts leading zeroes
func Clz(x uint64) uint64 {
	var n uint64

	n = 1

	if (x >> 32) == 0 {
		n = n + 32
		x = x << 32
	}
	if (x >> (32 + 16)) == 0 {
		n = n + 16
		x = x << 16
	}

	if (x >> (32 + 16 + 8)) == 0 {
		n = n + 8
		x = x << 8
	}

	if (x >> (32 + 16 + 8 + 4)) == 0 {
		n = n + 4
		x = x << 4
	}

	if (x >> (32 + 16 + 8 + 4 + 2)) == 0 {
		n = n + 2
		x = x << 2
	}

	n = n - (x >> 63)
	return uint64(n)
}