base64Binary.js
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/*
* @Author: zhang peng
* @Date: 2021-08-03 10:57:51
* @LastEditTime: 2021-08-16 17:25:43
* @LastEditors: zhang peng
* @Description:
* @FilePath: \miniprogram-to-uniapp2\src\project\template\polyfill\base64Binary.js
*
* 借鉴自：https://github.com/dankogai/js-base64/blob/main/base64.js
* 因uniapp没有window，也无法使用Buffer，因此直接使用polyfill
*
*/
const b64ch = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/='
const b64chs = [...b64ch]
const b64re = /^(?:[A-Za-z\d+\/]{4})*?(?:[A-Za-z\d+\/]{2}(?:==)?|[A-Za-z\d+\/]{3}=?)?$/
const b64tab = ((a) => {
let tab = {}
a.forEach((c, i) => tab[c] = i)
return tab
})(b64chs)
const _fromCC = String.fromCharCode.bind(String)
/**
* polyfill version of `btoa`
*/
const btoaPolyfill = (bin) => {
// console.log('polyfilled');
let u32, c0, c1, c2, asc = ''
const pad = bin.length % 3
for (let i = 0;i < bin.length;) {
if ((c0 = bin.charCodeAt(i++)) > 255 ||
(c1 = bin.charCodeAt(i++)) > 255 ||
(c2 = bin.charCodeAt(i++)) > 255)
throw new TypeError('invalid character found')
u32 = (c0 << 16) | (c1 << 8) | c2
asc += b64chs[u32 >> 18 & 63]
+ b64chs[u32 >> 12 & 63]
+ b64chs[u32 >> 6 & 63]
+ b64chs[u32 & 63]
}
return pad ? asc.slice(0, pad - 3) + "===".substring(pad) : asc
}
/**
* polyfill version of `atob`
*/
const atobPolyfill = (asc) => {
// console.log('polyfilled');
asc = asc.replace(/\s+/g, '')
if (!b64re.test(asc))
throw new TypeError('malformed base64.')
asc += '=='.slice(2 - (asc.length & 3))
let u24, bin = '', r1, r2
for (let i = 0;i < asc.length;) {
u24 = b64tab[asc.charAt(i++)] << 18
| b64tab[asc.charAt(i++)] << 12
| (r1 = b64tab[asc.charAt(i++)]) << 6
| (r2 = b64tab[asc.charAt(i++)])
bin += r1 === 64 ? _fromCC(u24 >> 16 & 255)
: r2 === 64 ? _fromCC(u24 >> 16 & 255, u24 >> 8 & 255)
: _fromCC(u24 >> 16 & 255, u24 >> 8 & 255, u24 & 255)
}
return bin
}
/**
* base64转ArrayBuffer
*/
function base64ToArrayBuffer (base64) {
const binaryStr = atobPolyfill(base64)
const byteLength = binaryStr.length
const bytes = new Uint8Array(byteLength)
for (let i = 0;i < byteLength;i++) {
bytes[i] = binary.charCodeAt(i)
}
return bytes.buffer
}
/**
* ArrayBuffer转base64
*/
function arrayBufferToBase64 (buffer) {
let binaryStr = ""
const bytes = new Uint8Array(buffer)
var len = bytes.byteLength
for (let i = 0;i < len;i++) {
binaryStr += String.fromCharCode(bytes[i])
}
return btoaPolyfill(binaryStr)
}
module.exports = {
base64ToArrayBuffer,
arrayBufferToBase64,
}