forked from p85947160/gitea
18 lines
514 B
Go
18 lines
514 B
Go
|
// +build !go1.9
|
||
|
|
|
||
|
|
package roaring
|
||
|
|
|
||
|
|
// bit population count, take from
|
||
|
|
// https://code.google.com/p/go/issues/detail?id=4988#c11
|
||
|
|
// credit: https://code.google.com/u/arnehormann/
|
||
|
|
// credit: https://play.golang.org/p/U7SogJ7psJ
|
||
|
|
// credit: http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
|
||
|
|
func popcount(x uint64) uint64 {
|
||
|
|
x -= (x >> 1) & 0x5555555555555555
|
||
|
|
x = (x>>2)&0x3333333333333333 + x&0x3333333333333333
|
||
|
|
x += x >> 4
|
||
|
|
x &= 0x0f0f0f0f0f0f0f0f
|
||
|
|
x *= 0x0101010101010101
|
||
|
|
return x >> 56
|
||
|
|
}
|