Golang - convert [8]bool to byte

Question

I am trying to convert a bool array of length 8 into a byte. Anyone know how?

mei := [8]bool{true, true, true, true, false, false, false, false}
myvar := ConvertToByte(mei)

AFAIK there's no simple way to do this in Go. So you'll need to write your own implementation. Here are some questions about the same thing in [Java](https://stackoverflow.com/questions/32048064/java-simple-boolean-to-byte-conversion) and [C#](https://stackoverflow.com/questions/24322417/how-to-convert-bool-array-in-one-byte-and-later-convert-back-in-bool-array) which might help you get started. — phonaputer, Sep 13 '22 at 23:55
`byte` is simply an alias for `uint8`; they are the same type. — Hymns For Disco, Sep 14 '22 at 00:30

malificent · Accepted Answer · 2022-09-14T04:02:59.130

Iterate through the bits, shifting and setting as you go.

Here's the code for the case where the most significant bit is at index 0 in the array:

func ConvertToUint8(mei [8]bool) uint8 {
    var result uint8
    for _, b := range mei {
        result <<= 1
        if b {
            result |= 1
        }
    }
    return result
}


mei := [8]bool{true, true, true, true, false, false, false, false}
myvar := ConvertToUint8(mei)
fmt.Printf("%b\n", myvar) // prints 11110000

Here's the code for the case where the least significant bit is at index 0 in the array:

func ConvertToUint8(mei [8]bool) uint8 {
    var result uint8
    for _, b := range mei {
        result >>= 1
        if b {
            result |= 0b10000000
        }
    }
    return result
}

mei := [8]bool{true, true, true, true, false, false, false, false}
myvar := ConvertToUint8(mei)
fmt.Printf("%08b\n", myvar) // prints 00001111

For converting to a uint8, is it the same thing but with `byte` replaced by `uint8`? — BAR, Sep 14 '22 at 00:32
@BAR [byte](https://pkg.go.dev/builtin#byte) is an [alias](https://go.dev/ref/spec#Alias_declarations) for uint8. Use either type. I edit answer to reduce confusion. — malificent, Sep 14 '22 at 01:20

score 2 · Answer 2 · answered Sep 14 '22 at 00:26

2

func ConvertToByte(bits [8]bool) byte {
    var b byte
    for _, bit := range bits {
        b <<= 1
        if bit {
            b |= 1
        }
    }
    return b
}

answered Sep 14 '22 at 00:26

Hymns For Disco

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For converting to a uint8, is it the same thing but with byte replaced by uint8? – BAR Sep 14 '22 at 00:33
@BAR See my other comment, but `byte` and `uint8` are just 2 words to refer to the exact same type in Go. You can replace any or all occurrences of `byte` with `uint8` or vice versa and it will be the same program. Use whichever one you prefer. – Hymns For Disco Sep 14 '22 at 01:04

score -1 · Answer 3 · answered Sep 14 '22 at 18:56

-1

Just a little bit-twiddling. Iterate over the array:

func boolsToByte( flags [8]bool ) (b byte) {
    mask := byte(0x80)
    for _, f := range flags {
        if f {
            b |= mask
        }
        mask >>= 1
    }
    return b
}

answered Sep 14 '22 at 18:56

Nicholas Carey

71,308
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Golang - convert [8]bool to byte

3 Answers3