Transfer: ArrayBuffer、Base64、Hex、String

[54leibo]

• ArrayBuffer <=> String:

const _arrayBufferToString = arrayBuffer => 
    String.fromCharCode(...new Uint16Array(arrayBuffer))

const _stringToArrayBuffer = str => 
    Uint16Array.from(str, c => c.charCodeAt(0)).buffer

// example
const str = '123'
const buf = _stringToArrayBuffer(str)
console.log(str, _arrayBufferToString(buf))

• ArrayBuffer <=> Base64

const _arrayBufferToBase64 = arrayBuffer => 
    btoa(String.fromCharCode(...new Uint16Array(arrayBuffer)))

const _base64ToArrayBuffer = base64 => 
    Uint16Array.from(atob(base64), c => c.charCodeAt(0)).buffer
    
// example
const base64 = window.btoa('123')
const buf = _base64ToArrayBuffer(base64)
console.log(base64, _arrayBufferToBase64(buf))

• ArrayBuffer <=> Hex

const _arrayBufferToHex = (arrayBuffer) => 
    Array.prototype.map.call(new Uint16Array(arrayBuffer), x => ('00' + x.toString(16)).slice(-2)).join('')

const _hexToArrayBuffer = (str) => {
    const len = str.length
    const arrayBuffer = new ArrayBuffer(len)
    const uint16 = new Uint16Array(arrayBuffer)
    let b;
    
    for (let i=0, j=0; i<len; i+=2) {
        b = parseInt(str.substring(i, i+2), 16)
        uint16[j++] = b
    }
    
    return arrayBuffer;
}

// example
const hex = "39b2abc192db9bc9175de7e5f9e7ef08"
const buffer = _hexToArrayBuffer(hex);
console.log(hex, _arrayBufferToHex(buffer), hex === _arrayBufferToHex(buffer))