base64.ts

/*\
|*|
|*|  Base64 / binary data / UTF-8 strings utilities
|*|
|*|  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Base64_encoding_and_decoding
|*|
\*/

/* Array of bytes to Base64 string decoding */

function b64ToUint6(nChr: number): number {
  return nChr > 64 && nChr < 91
    ? nChr - 65
    : nChr > 96 && nChr < 123
    ? nChr - 71
    : nChr > 47 && nChr < 58
    ? nChr + 4
    : nChr === 43
    ? 62
    : 63;
}

export function base64Decode(str: string): Uint8Array {
  var sB64Enc = str
      .replace(/[,_]/g, '/')
      .replace(/[-]/g, '+')
      .replace(/[^A-Za-z0-9\+\/]/g, ''),
    nInLen = sB64Enc.length,
    nOutLen = (nInLen * 3 + 1) >> 2,
    taBytes = new Uint8Array(nOutLen);

  for (
    var nMod3, nMod4, nUint24 = 0, nOutIdx = 0, nInIdx = 0;
    nInIdx < nInLen;
    nInIdx++
  ) {
    nMod4 = nInIdx & 3;
    nUint24 |= b64ToUint6(sB64Enc.charCodeAt(nInIdx)) << (6 * (3 - nMod4));
    if (nMod4 === 3 || nInLen - nInIdx === 1) {
      for (nMod3 = 0; nMod3 < 3 && nOutIdx < nOutLen; nMod3++, nOutIdx++) {
        taBytes[nOutIdx] = (nUint24 >>> ((16 >>> nMod3) & 24)) & 255;
      }
      nUint24 = 0;
    }
  }

  return taBytes;
}

/* Base64 string to array encoding */

function uint6ToB64(nUint6: number): number {
  return nUint6 < 26
    ? nUint6 + 65
    : nUint6 < 52
    ? nUint6 + 71
    : nUint6 < 62
    ? nUint6 - 4
    : nUint6 === 62
    ? 43
    : 47;
}

export function base64Encode(bytes: Uint8Array): string {
  var nMod3 = 2,
    sB64Enc = '';

  for (var nLen = bytes.length, nUint24 = 0, nIdx = 0; nIdx < nLen; nIdx++) {
    nMod3 = nIdx % 3;
    nUint24 |= bytes[nIdx] << ((16 >>> nMod3) & 24);
    if (nMod3 === 2 || bytes.length - nIdx === 1) {
      sB64Enc += String.fromCodePoint(
        uint6ToB64((nUint24 >>> 18) & 63),
        uint6ToB64((nUint24 >>> 12) & 63),
        uint6ToB64((nUint24 >>> 6) & 63),
        uint6ToB64(nUint24 & 63),
      );
      nUint24 = 0;
    }
  }

  return (
    sB64Enc.substr(0, sB64Enc.length - 2 + nMod3) +
    (nMod3 === 2 ? '' : nMod3 === 1 ? '=' : '==')
  );
}

/* UTF-8 array to DOMString and vice versa */

export function unicodeToString(bytes: Uint8Array): string {
  const utf8decoder = new TextDecoder();
  return utf8decoder.decode(bytes);
}

export function stringToUnicode(str: string): Uint8Array {
  const utf8encoder = new TextEncoder();
  return utf8encoder.encode(str);
}