布尔数组到字节数组

Question

I have function to convert a byte array to a bool array representing 0s and 1s:

func byteArrayToBoolArray(ba []byte) []bool {
    var s []bool

    for _, b := range ba {
        for _, c := range strconv.FormatUint(uint64(by), 2) {
            s = append(s, c == []rune("1")[0])
        }
    }

    return s
}

How does a function look like that does exactly the opposite, meaning converting a bool array into a byte array?

Edit: This playground give more details how my byte array may look like: https://play.golang.org/p/tEDcZv-t_0Q

ba := []byte{123, 255}

Answer 1

For example, boolsToBytes, the inverse (exactly the opposite) of bytesToBools,

package main

import (
    "fmt"
)

func boolsToBytes(t []bool) []byte {
    b := make([]byte, (len(t)+7)/8)
    for i, x := range t {
        if x {
            b[i/8] |= 0x80 >> uint(i%8)
        }
    }
    return b
}

func bytesToBools(b []byte) []bool {
    t := make([]bool, 8*len(b))
    for i, x := range b {
        for j := 0; j < 8; j++ {
            if (x<<uint(j))&0x80 == 0x80 {
                t[8*i+j] = true
            }
        }
    }
    return t
}

func main() {
    b := []byte{123, 255}
    fmt.Println(b)
    t := bytesToBools(b)
    fmt.Printf("%t
", t)
    b = boolsToBytes(t)
    fmt.Println(b)
}

Playground: https://play.golang.org/p/IguJ_4cZKtA

Output:

[123 255]
[false true true true true false true true true true true true true true true true]
[123 255]

---

The question provides a function and asks for an inverse (does exactly the opposite) function.

The question function algorithm is flawed, several inputs map to the same function value. Therefore, there is no unique inverse.

package main

import (
    "fmt"
    "strconv"
)

func byteArrayToBoolArray(ba []byte) []bool {
    var s []bool
    for _, b := range ba {
        for _, c := range strconv.FormatUint(uint64(b), 2) {
            s = append(s, c == []rune("1")[0])
        }
    }
    return s
}

func main() {
    ba1 := []byte{0xF}
    fmt.Println(byteArrayToBoolArray(ba1))
    ba2 := []byte{0x3, 0x3}
    fmt.Println(byteArrayToBoolArray(ba2))
    ba3 := []byte{0x1, 0x1, 0x1, 0x1}
    fmt.Println(byteArrayToBoolArray(ba3))
}

Playground: https://play.golang.org/p/L9VsTtbkQZW

Output:

[true true true true]
[true true true true]
[true true true true]