Function decodeUtf8

blue_modules/uint8array-extras/index.js:368–410

* Minimal UTF-8 decoder * @param {Uint8Array} bytes * @returns {string}

(bytes)

 * @returns {string}
 */
function decodeUtf8(bytes) {
  let i = 0;
  const l = bytes.length;
  const codeUnits = [];
  let result = '';

  while (i < l) {
    const byte1 = bytes[i++];

    // 1-byte (ASCII)
    if (byte1 < 0x80) {
      codeUnits.push(byte1);
    }
    // 2-byte
    else if (byte1 < 0xe0) {
      const byte2 = bytes[i++] & 0x3f;
      codeUnits.push(((byte1 & 0x1f) << 6) | byte2);
    }
    // 3-byte
    else if (byte1 < 0xf0) {
      const byte2 = bytes[i++] & 0x3f;
      const byte3 = bytes[i++] & 0x3f;
      codeUnits.push(((byte1 & 0x0f) << 12) | (byte2 << 6) | byte3);
    }
    // 4-byte (→ surrogate pair)
    else {
      const byte2 = bytes[i++] & 0x3f;
      const byte3 = bytes[i++] & 0x3f;
      const byte4 = bytes[i++] & 0x3f;
      let cp = ((byte1 & 0x07) << 18) | (byte2 << 12) | (byte3 << 6) | byte4;
      cp -= 0x10000;
      codeUnits.push(0xd800 + (cp >> 10), 0xdc00 + (cp & 0x3ff));
    }

    // Flush periodically to avoid huge apply() calls
    if (codeUnits.length > 0x8000) {
      result += String.fromCharCode.apply(null, codeUnits);
      codeUnits.length = 0;
    }
  }

  return result + String.fromCharCode.apply(null, codeUnits);
}