如何将 uint8 数组转换为 base64 编码字符串? [英] How to convert uint8 Array to base64 Encoded String?

问题描述

我有一个 webSocket 通信，我收到 base64 编码的字符串，将其转换为 uint8 并对其进行处理，但现在我需要发回，我得到了 uint8 数组，并且需要将其转换为 base64 字符串，所以我可以发送.我该如何进行这种转换?

解决方案

所有已经提出的解决方案都有严重的问题.一些解决方案无法在大型数组上工作，一些提供错误的输出，如果中间字符串包含多字节字符，一些解决方案会在 btoa 调用时抛出错误，一些消耗的内存超过所需.

所以我实现了一个直接转换功能，无论输入如何，它都可以工作.它在我的机器上每秒转换大约 500 万字节.

https://gist.github.com/enepomnyaschih/72c423f727d39823ea727d397387a0p

/*麻省理工学院执照版权所有 (c) 2020 Egor Nepomnyaschih特此向任何获得副本的人免费授予许可本软件和相关文档文件(软件")，以处理在软件中不受限制，包括但不限于权利使用、复制、修改、合并、发布、分发、再许可和/或出售软件的副本，并允许软件的接收者提供这样做，但须符合以下条件:以上版权声明和本许可声明应包含在所有本软件的副本或重要部分.本软件按原样"提供，不提供任何形式的明示或保证暗示，包括但不限于适销性保证，适用于特定目的且不侵权.在任何情况下都不得作者或版权持有人应对任何索赔、损害或其他责任，无论是在合同诉讼、侵权行为或其他方面，由以下原因引起的，与本软件或本软件的使用或其他交易无关或与之相关软件.*//*//这个常数也可以用下面的算法计算:const base64abc = [],A = "A".charCodeAt(0),a = "a".charCodeAt(0),n = "0".charCodeAt(0);for (让 i = 0; i <26; ++i) {base64abc.push(String.fromCharCode(A + i));}for (让 i = 0; i <26; ++i) {base64abc.push(String.fromCharCode(a + i));}for (让 i = 0; i <10; ++i) {base64abc.push(String.fromCharCode(n + i));}base64abc.push("+");base64abc.push("/");*/const base64abc = [A"、B"、C"、D"、E"、F"、G"、H"、I"、J"、K"、L"、M""，N"、O"、P"、Q"、R"、S"、T"、U"、V"、W"、X"、Y"、Z""，"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m"，"n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"，0"、1"、2"、3"、4"、5"、6"、7"、8"、9"、+"、/"];/*//这个常数也可以用下面的算法计算:const l = 256, base64codes = new Uint8Array(l);for (让 i = 0; i < l; ++i) {base64codes[i] = 255;//无效字符}base64abc.forEach((char, index) => {base64codes[char.charCodeAt(0)] = 索引；});base64codes["=".charCodeAt(0)] = 0;//无论如何都被忽略了，所以我们只需要防止错误*/const base64codes = [255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 62, 255, 255, 255, 63,52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 255, 255, 255, 0, 255, 255,255, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 255, 255, 255, 255, 255,255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51];函数 getBase64Code(charCode) {if (charCode >= base64codes.length) {throw new Error("无法解析base64字符串.");}常量代码 = base64codes[charCode];如果(代码 === 255){throw new Error("无法解析base64字符串.");}返回码；}导出函数 bytesToBase64(bytes) {让结果 = '', i, l = bytes.length;对于 (i = 2; i >2];结果 += base64abc[((bytes[i - 2] & 0x03) << 4) |(字节[i - 1] > > 4)];结果 += base64abc[((bytes[i - 1] & 0x0F) << 2) |(字节[i]＞＞6)]；结果 += base64abc[bytes[i] &0x3F];}if (i === l + 1) {//1 个八位字节尚未写入结果 += base64abc[bytes[i - 2] >>2];结果 += base64abc[(bytes[i - 2] & 0x03) <<4];结果 += "==";}if (i === l) {//2 个八位字节尚未写入结果 += base64abc[bytes[i - 2] >>2];结果 += base64abc[((bytes[i - 2] & 0x03) << 4) |(字节[i - 1] > > 4)];结果 += base64abc[(bytes[i - 1] & 0x0F) <<2];结果+=="；}返回结果；}导出函数 base64ToBytes(str) {if (str.length % 4 !== 0) {throw new Error("无法解析base64字符串.");}const index = str.indexOf("=");if (index !== -1 && index < str.length - 2) {throw new Error("无法解析base64字符串.");}让 missingOctets = str.endsWith("==") ?2 : str.endsWith("=") ?1 : 0,n = 字符串长度，结果 = 新的 Uint8Array(3 * (n/4)),缓冲;for (让 i = 0, j = 0; i 

I got a webSocket comunication, I recieve base64 encoded string, convert it to uint8 and work on it, but now I need to send back, I got the uint8 array, and need to convert it to base64 string, so I can send it. How can I make this convertion?

解决方案

All solutions already proposed have severe problems. Some solutions fail to work on large arrays, some provide wrong output, some throw an error on btoa call if an intermediate string contains multibyte characters, some consume more memory than needed.

So I implemented a direct conversion function which just works regardless of the input. It converts about 5 million bytes per second on my machine.

https://gist.github.com/enepomnyaschih/72c423f727d395eeaa09697058238727

/*
MIT License
Copyright (c) 2020 Egor Nepomnyaschih
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

/*
// This constant can also be computed with the following algorithm:
const base64abc = [],
	A = "A".charCodeAt(0),
	a = "a".charCodeAt(0),
	n = "0".charCodeAt(0);
for (let i = 0; i < 26; ++i) {
	base64abc.push(String.fromCharCode(A + i));
}
for (let i = 0; i < 26; ++i) {
	base64abc.push(String.fromCharCode(a + i));
}
for (let i = 0; i < 10; ++i) {
	base64abc.push(String.fromCharCode(n + i));
}
base64abc.push("+");
base64abc.push("/");
*/
const base64abc = [
	"A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
	"N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z",
	"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m",
	"n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z",
	"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "+", "/"
];

/*
// This constant can also be computed with the following algorithm:
const l = 256, base64codes = new Uint8Array(l);
for (let i = 0; i < l; ++i) {
	base64codes[i] = 255; // invalid character
}
base64abc.forEach((char, index) => {
	base64codes[char.charCodeAt(0)] = index;
});
base64codes["=".charCodeAt(0)] = 0; // ignored anyway, so we just need to prevent an error
*/
const base64codes = [
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 62, 255, 255, 255, 63,
	52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 255, 255, 255, 0, 255, 255,
	255, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
	15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 255, 255, 255, 255, 255,
	255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
	41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
];

function getBase64Code(charCode) {
	if (charCode >= base64codes.length) {
		throw new Error("Unable to parse base64 string.");
	}
	const code = base64codes[charCode];
	if (code === 255) {
		throw new Error("Unable to parse base64 string.");
	}
	return code;
}

export function bytesToBase64(bytes) {
	let result = '', i, l = bytes.length;
	for (i = 2; i < l; i += 3) {
		result += base64abc[bytes[i - 2] >> 2];
		result += base64abc[((bytes[i - 2] & 0x03) << 4) | (bytes[i - 1] >> 4)];
		result += base64abc[((bytes[i - 1] & 0x0F) << 2) | (bytes[i] >> 6)];
		result += base64abc[bytes[i] & 0x3F];
	}
	if (i === l + 1) { // 1 octet yet to write
		result += base64abc[bytes[i - 2] >> 2];
		result += base64abc[(bytes[i - 2] & 0x03) << 4];
		result += "==";
	}
	if (i === l) { // 2 octets yet to write
		result += base64abc[bytes[i - 2] >> 2];
		result += base64abc[((bytes[i - 2] & 0x03) << 4) | (bytes[i - 1] >> 4)];
		result += base64abc[(bytes[i - 1] & 0x0F) << 2];
		result += "=";
	}
	return result;
}

export function base64ToBytes(str) {
	if (str.length % 4 !== 0) {
		throw new Error("Unable to parse base64 string.");
	}
	const index = str.indexOf("=");
	if (index !== -1 && index < str.length - 2) {
		throw new Error("Unable to parse base64 string.");
	}
	let missingOctets = str.endsWith("==") ? 2 : str.endsWith("=") ? 1 : 0,
		n = str.length,
		result = new Uint8Array(3 * (n / 4)),
		buffer;
	for (let i = 0, j = 0; i < n; i += 4, j += 3) {
		buffer =
			getBase64Code(str.charCodeAt(i)) << 18 |
			getBase64Code(str.charCodeAt(i + 1)) << 12 |
			getBase64Code(str.charCodeAt(i + 2)) << 6 |
			getBase64Code(str.charCodeAt(i + 3));
		result[j] = buffer >> 16;
		result[j + 1] = (buffer >> 8) & 0xFF;
		result[j + 2] = buffer & 0xFF;
	}
	return result.subarray(0, result.length - missingOctets);
}

export function base64encode(str, encoder = new TextEncoder()) {
	return bytesToBase64(encoder.encode(str));
}

export function base64decode(str, decoder = new TextDecoder()) {
	return decoder.decode(base64ToBytes(str));
}

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