Convert []string to []byte

Question

I am looking to convert a string array to a byte array in GO so I can write it down to a disk. What is an optimal solution to encode and decode a string array ([]string

Answer 1

To illustrate the problem, convert []string to []byte and then convert []byte back to []string, here's a simple solution:

package main

import (
    "encoding/binary"
    "fmt"
)

const maxInt32 = 1<<(32-1) - 1

func writeLen(b []byte, l int) []byte {
    if 0 > l || l > maxInt32 {
        panic("writeLen: invalid length")
    }
    var lb [4]byte
    binary.BigEndian.PutUint32(lb[:], uint32(l))
    return append(b, lb[:]...)
}

func readLen(b []byte) ([]byte, int) {
    if len(b) < 4 {
        panic("readLen: invalid length")
    }
    l := binary.BigEndian.Uint32(b)
    if l > maxInt32 {
        panic("readLen: invalid length")
    }
    return b[4:], int(l)
}

func Decode(b []byte) []string {
    b, ls := readLen(b)
    s := make([]string, ls)
    for i := range s {
        b, ls = readLen(b)
        s[i] = string(b[:ls])
        b = b[ls:]
    }
    return s
}

func Encode(s []string) []byte {
    var b []byte
    b = writeLen(b, len(s))
    for _, ss := range s {
        b = writeLen(b, len(ss))
        b = append(b, ss...)
    }
    return b
}

func codecEqual(s []string) bool {
    return fmt.Sprint(s) == fmt.Sprint(Decode(Encode(s)))
}

func main() {
    var s []string
    fmt.Println("equal", codecEqual(s))
    s = []string{"", "a", "bc"}
    e := Encode(s)
    d := Decode(e)
    fmt.Println("s", len(s), s)
    fmt.Println("e", len(e), e)
    fmt.Println("d", len(d), d)
    fmt.Println("equal", codecEqual(s))
}

Output:

equal true
s 3 [ a bc]
e 19 [0 0 0 3 0 0 0 0 0 0 0 1 97 0 0 0 2 98 99]
d 3 [ a bc]
equal true