Extract bits into a int slice from byte slice

问题

I have following byte slice which from which i need to extract bits and place them in a []int as i intend to fetch individual bit values later. I am having a hard time figuring out how to do that.

below is my code

data := []byte{3 255}//binary representation is for 3 and 255 is 00000011 11111111

what i need is a slice of bits -- > [0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1]

What i tried

• I tried converting byte slice to Uint16 with BigEndian and then tried to use strconv.FormatUint but that fails with error panic: runtime error: index out of range
• Saw many examples that simple output bit representation of number using fmt.Printf function but that is not useful for me as i need a int slice for further bit value access.

Do i need to use bit shift operators here ? Any help will be greatly appreciated.

回答1:

One way is to loop over the bytes, and use a 2nd loop to shift the byte values bit-by-bit and test for the bits with a bitmask. And add the result to the output slice.

Here's an implementation of it:

func bits(bs []byte) []int {
    r := make([]int, len(bs)*8)
    for i, b := range bs {
        for j := 0; j < 8; j++ {
            r[i*8+j] = int(b >> uint(7-j) & 0x01)
        }
    }
    return r
}

Testing it:

fmt.Println(bits([]byte{3, 255}))

Output (try it on the Go Playground):

[0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1]

回答2:

Using the bits package provides a fairly straightforward solution.

func bitsToBits(data []byte) (st []int) {
    st = make([]int, len(data)*8) // Performance x 2 as no append occurs.
    for i, d := range data {
        for j := 0; j < 8; j++ {
            if bits.LeadingZeros8(d) == 0 {
                // No leading 0 means that it is a 1
                st[i*8+j] = 1
            } else {
                st[i*8+j] = 0
            }
            d = d << 1
        }
    }
    return
}

Performance is comparable to similar solutions.

来源：https://stackoverflow.com/questions/52811744/extract-bits-into-a-int-slice-from-byte-slice