/* https://developer.mozilla.org/en-US/docs/Web/JavaScript/Base64_encoding_and_decoding */

exports.fromUTF8Arr = UTF8ArrToStr
exports.toUTF8Arr = strToUTF8Arr

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

function UTF8ArrToStr (aBytes) {

  var sView = "";

  for (var nPart, nLen = aBytes.length, nIdx = 0; nIdx < nLen; nIdx++) {
    nPart = aBytes[nIdx];
    sView += String.fromCharCode(
      nPart > 251 && nPart < 254 && nIdx + 5 < nLen ? /* six bytes */
        /* (nPart - 252 << 32) is not possible in ECMAScript! So...: */
        (nPart - 252) * 1073741824 + (aBytes[++nIdx] - 128 << 24) + (aBytes[++nIdx] - 128 << 18) + (aBytes[++nIdx] - 128 << 12) + (aBytes[++nIdx] - 128 << 6) + aBytes[++nIdx] - 128
      : nPart > 247 && nPart < 252 && nIdx + 4 < nLen ? /* five bytes */
        (nPart - 248 << 24) + (aBytes[++nIdx] - 128 << 18) + (aBytes[++nIdx] - 128 << 12) + (aBytes[++nIdx] - 128 << 6) + aBytes[++nIdx] - 128
      : nPart > 239 && nPart < 248 && nIdx + 3 < nLen ? /* four bytes */
        (nPart - 240 << 18) + (aBytes[++nIdx] - 128 << 12) + (aBytes[++nIdx] - 128 << 6) + aBytes[++nIdx] - 128
      : nPart > 223 && nPart < 240 && nIdx + 2 < nLen ? /* three bytes */
        (nPart - 224 << 12) + (aBytes[++nIdx] - 128 << 6) + aBytes[++nIdx] - 128
      : nPart > 191 && nPart < 224 && nIdx + 1 < nLen ? /* two bytes */
        (nPart - 192 << 6) + aBytes[++nIdx] - 128
      : /* nPart < 127 ? */ /* one byte */
        nPart
    );
  }

  return sView;

}

function strToUTF8Arr (sDOMStr) {

    var aBytes, nChr, nStrLen = sDOMStr.length, nArrLen = 0;

    /* mapping... */

    for (var nMapIdx = 0; nMapIdx < nStrLen; nMapIdx++) {
        nChr = sDOMStr.charCodeAt(nMapIdx);
        nArrLen += nChr < 0x80 ? 1 : nChr < 0x800 ? 2 : nChr < 0x10000 ? 3 : nChr < 0x200000 ? 4 : nChr < 0x4000000 ? 5 : 6;
    }

    aBytes = new Uint8Array(nArrLen);

    /* transcription... */

    for (var nIdx = 0, nChrIdx = 0; nIdx < nArrLen; nChrIdx++) {
        nChr = sDOMStr.charCodeAt(nChrIdx);
        if (nChr < 128) {
            /* one byte */
            aBytes[nIdx++] = nChr;
        } else if (nChr < 0x800) {
            /* two bytes */
            aBytes[nIdx++] = 192 + (nChr >>> 6);
            aBytes[nIdx++] = 128 + (nChr & 63);
        } else if (nChr < 0x10000) {
            /* three bytes */
            aBytes[nIdx++] = 224 + (nChr >>> 12);
            aBytes[nIdx++] = 128 + (nChr >>> 6 & 63);
            aBytes[nIdx++] = 128 + (nChr & 63);
        } else if (nChr < 0x200000) {
            /* four bytes */
            aBytes[nIdx++] = 240 + (nChr >>> 18);
            aBytes[nIdx++] = 128 + (nChr >>> 12 & 63);
            aBytes[nIdx++] = 128 + (nChr >>> 6 & 63);
            aBytes[nIdx++] = 128 + (nChr & 63);
        } else if (nChr < 0x4000000) {
            /* five bytes */
            aBytes[nIdx++] = 248 + (nChr >>> 24);
            aBytes[nIdx++] = 128 + (nChr >>> 18 & 63);
            aBytes[nIdx++] = 128 + (nChr >>> 12 & 63);
            aBytes[nIdx++] = 128 + (nChr >>> 6 & 63);
            aBytes[nIdx++] = 128 + (nChr & 63);
        } else /* if (nChr <= 0x7fffffff) */ {
            /* six bytes */
            aBytes[nIdx++] = 252 + /* (nChr >>> 32) is not possible in ECMAScript! So...: */ (nChr / 1073741824);
            aBytes[nIdx++] = 128 + (nChr >>> 24 & 63);
            aBytes[nIdx++] = 128 + (nChr >>> 18 & 63);
            aBytes[nIdx++] = 128 + (nChr >>> 12 & 63);
            aBytes[nIdx++] = 128 + (nChr >>> 6 & 63);
            aBytes[nIdx++] = 128 + (nChr & 63);
        }
    }

    return aBytes;

}