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Encode an ArrayBuffer as a base64 string
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const base64_encode_std = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/' | |
const base64_encode_url = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_' | |
const base64_decode = [{}, {}, {}, {}] | |
{ | |
const add = (k, i) => { | |
base64_decode[0][k] = i << 0 | |
base64_decode[1][k] = i << 6 | |
base64_decode[2][k] = i << 12 | |
base64_decode[3][k] = i << 18 | |
} | |
for (let i=0; i<64; i++) | |
add(base64_encode_std[i], i) | |
add('-', 62) | |
add('_', 63) | |
add('=', 0) | |
} | |
const arrBase64 = bindArrayBufferBase64() | |
function bindArrayBufferBase64(enc, pad) { | |
const [dec_d, dec_c, dec_b, dec_a] = base64_decode | |
if (!enc) { | |
enc = base64_encode_std | |
if (null == pad) pad = '=' | |
} else if (true === enc) { | |
enc = base64_encode_url | |
pad = '' | |
} | |
if (null == pad) pad = '' | |
return { pack, unpack } | |
function pack(arrayBuffer) { | |
const z = new Uint8Array(arrayBuffer.buffer || arrayBuffer) | |
const rem = z.byteLength % 3, len = z.byteLength - rem | |
let res = '' | |
for (let i=0; i < len; i+=3) { | |
const a = z[i] >>> 2 | |
const b = 0x3f & ( (z[i] << 4) | (z[i+1] >>> 4) ) | |
const c = 0x3f & ( (z[i+1] << 2) | (z[i+2] >>> 6) ) | |
const d = 0x3f & z[i+2] | |
res += `${enc[a]}${enc[b]}${enc[c]}${enc[d]}` | |
} | |
if (2 === rem) { | |
const a = z[len] >>> 2 | |
const b = 0x3f & ( (z[len] << 4) | (z[len+1] >>> 4) ) | |
const c = 0x0f & z[len+1] | |
res += `${enc[a]}${enc[b]}${enc[c]}${pad}` | |
} else if (1 === rem) { | |
const a = z[len] >> 2 | |
const b = 0x03 & z[len] | |
res += `${enc[a]}${enc[b]}${pad}${pad}` | |
} | |
return res | |
} | |
function unpack(str) { | |
let len=str.length, rem=len&3 | |
if (0 === rem) { | |
const pad = str.slice(-2) | |
rem = ('='!==pad[1] ? 0 : '='!==pad[0] ? 2 : 1) | |
len = 3*(len-rem >> 2) //+ rem | |
} else { | |
rem -= 1 | |
len = 3*(len >> 2) //+ rem | |
} | |
const z = new Uint8Array(len) | |
let i=0,j=0 | |
for (; i<len; i+=3,j+=4) { | |
const v = dec_a[str[j]] | dec_b[str[j+1]] | dec_c[str[j+2]] | dec_d[str[j+3]] | |
z[ i ] = 0xff & (v >>> 16) | |
z[i+1] = 0xff & (v >>> 8) | |
z[i+2] = 0xff & v | |
} | |
if (2 === rem) { | |
const v = dec_b[str[j]] | dec_c[str[j+1]] | dec_d[str[j+2]] | |
z[ i ] = 0xff & (v >>> 8) | |
z[i+1] = 0xff & v | |
} else if (1 === rem) { | |
const v = dec_c[str[j]] | dec_d[str[j+1]] | |
z[ i ] = 0xff & v | |
} | |
return z | |
} | |
} |
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const {randomBytes} = require('crypto') | |
function test(count=1, width=64) { | |
if (0 > width) width = 0 | 1 - width * Math.random() | |
while (--count > 0) { | |
const b0 = new Uint8Array(randomBytes(width)) | |
const sz_b64 = arrBase64.pack(b0) | |
const b1 = arrBase64.unpack(sz_b64) | |
const b2 = Array.from(b0, (v,i) => ((b1[i] - v) || '')) | |
console.log(b2.join('.')) | |
} | |
} | |
console.log() | |
test(10, 63) | |
console.log() | |
test(10, 64) | |
console.log() | |
test(10, 65) |
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