在Golang中，如何计算字节中有多少个比特？

Question

Suppose I have two variables, that only use 6 bits:

var a byte = 31  // 00011111
var b byte = 50  // 00110010

The first (a) have more one bits than the b, however the b is greater than a of course, so is not possible use a > b.

To achieve what I need, I do one loop:

func countOneBits(byt byte) int {
    var counter int
    var divider byte

    for divider = 32; divider >= 1; divider >>= 1 {
        if byt & divider == divider {
            counter++
        }

    }

    return counter
}

This works, I can use countOneBits(a) > countOneBits(b)...

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But I don't think is the best solution for this case, I don't think this need a loop and because of it I'm here.

Have a better alternative (in performance aspect) to count how many 1 have in six bits?

Answer 1

Given that the input is a single byte probably a lookup table is the best option... only takes 256 bytes and you get code like

var count = bitcount[input];