Golang: Curious Case of Returning Byte Array and Conversion to Byte Slice

For this article, just want to highlight a peculiar way to return byte array. Looking a the returnByteArray() function, notice that the return type is actually a concrete “array”. To return it, you can use copy (an in-built) function to copy over content to your array. Then return “empty”.

package main
import (
        "fmt"
)
func returnByteArray() (array [5]byte) {
byteSlice := []byte("Loves you")
        copy(array[:], byteSlice[0:5])
        return
}
func main() {
        byteArray := returnByteArray()
        fmt.Println(string(byteArray[:])) // convert byte array to byte slice and string
}

From the main program, you also can see how to use the byteArray[:] to convert back to a byteSlice. Out of the program is as follows:

$ go run main.go
Loves

Of course, you can use the usual syntax. See returnByteArrayUsual() and things will work fine.

package main
import (
        "fmt"
)
func returnByteArray() (array [5]byte) {
byteSlice := []byte("Loves you")
        copy(array[:], byteSlice[0:5])
        return
}
func returnByteArrayUsual() [5]byte {
        byteSlice := []byte("Loves you")
        var array [5]byte
        copy(array[:], byteSlice[0:5])
        return array
}
func main() {
        byteArray := returnByteArray()
        fmt.Println(string(byteArray[:])) // convert byte array to byte slice and string
byteArray = returnByteArrayUsual()
        fmt.Println(string(byteArray[:])) // convert byte array to byte slice and string
}