prometheus/vendor/github.com/dgryski/go-bits/clz.go

38 lines
466 B
Go

// +build !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)
}