javascript - 如何在 node.js 中将位字符串转换为 base64？

Question

我有一个要转换为 base64 的位字符串，但看起来没有本地函数可以执行此操作，而且我也找不到节点模块。):

输入：100110110101000110100011011001100010110100011011001100100110100011000001100000110000011000001100001001010100111110000011001111100101010011111010011100010110001001001001100000110100111010010100111110000111001000100000110001001000101100111110011001001001101011010001011001001101001010000011000100100100110000011010011

输出：该等效二进制值的 base64 表示

也许更好的问题是如何将位字符串转换为缓冲区？没有把握

标签： javascriptnode.jsbinarybase64bit-manipulation

Answer 1

正如您所猜测的，主要是将字符串转换为更容易转换为 base64 的字符串，然后再将其转换为 base64。

在下面的代码中，我们执行这些转换序列：

• 位字符串 -> BigInt -> 字节大小的整数数组 -> 二进制字符串 -> base64
• base64 -> 二进制字符串 -> 字节大小的位字符串数组 -> 位字符串

const encode = bitstr => {
  const bytes = [];
  // convert bit string to BigInt
  let value = BigInt('0b' + bitstr);
  // chop it up into bytes
  while (value > 0n) {
    bytes.unshift(Number(value & 0xffn));
    value >>= 8n;
  }
  // convert to binary string and encode as base64
  return btoa(String.fromCharCode.apply(null, bytes));
};

const decode = b64 => {
  // decode base64 to binary string
  const bstr = atob(b64);
  // convert binary string to bit string
  return new Array(bstr.length).fill(0).map(
    (_,i) => bstr.charCodeAt(i).toString(2).padStart(8, i ? '0' : '')
  ).join('');
};

const bitstr = '100110110101000110100011011001100010110100011011001100100110100011000001100000110000011000001100001001010100111110000011001111100101010011111010011100010110001001001001100000110100111010010100111110000111001000100000110001001000101100111110011001001001101011010001011001001101001010000011000100100100110000011010011';
const encoded = encode(bitstr);
const decoded = decode(encoded);

console.log(bitstr);
console.log(encoded);
console.log(decoded);