Function UTF8ArrayToString

js/sql-debug.js:738–782

(u8Array, idx)

var UTF8Decoder = typeof TextDecoder !== 'undefined' ? new TextDecoder('utf8') : undefined;
function UTF8ArrayToString(u8Array, idx) {
  var endPtr = idx;
  // TextDecoder needs to know the byte length in advance, it doesn't stop on null terminator by itself.
  // Also, use the length info to avoid running tiny strings through TextDecoder, since .subarray() allocates garbage.
  while (u8Array[endPtr]) ++endPtr;

  if (endPtr - idx > 16 && u8Array.subarray && UTF8Decoder) {
    return UTF8Decoder.decode(u8Array.subarray(idx, endPtr));
  } else {
    var u0, u1, u2, u3, u4, u5;

    var str = '';
    while (1) {
      // For UTF8 byte structure, see http://en.wikipedia.org/wiki/UTF-8#Description and https://www.ietf.org/rfc/rfc2279.txt and https://tools.ietf.org/html/rfc3629
      u0 = u8Array[idx++];
      if (!u0) return str;
      if (!(u0 & 0x80)) { str += String.fromCharCode(u0); continue; }
      u1 = u8Array[idx++] & 63;
      if ((u0 & 0xE0) == 0xC0) { str += String.fromCharCode(((u0 & 31) << 6) | u1); continue; }
      u2 = u8Array[idx++] & 63;
      if ((u0 & 0xF0) == 0xE0) {
        u0 = ((u0 & 15) << 12) | (u1 << 6) | u2;
      } else {
        u3 = u8Array[idx++] & 63;
        if ((u0 & 0xF8) == 0xF0) {
          u0 = ((u0 & 7) << 18) | (u1 << 12) | (u2 << 6) | u3;
        } else {
          u4 = u8Array[idx++] & 63;
          if ((u0 & 0xFC) == 0xF8) {
            u0 = ((u0 & 3) << 24) | (u1 << 18) | (u2 << 12) | (u3 << 6) | u4;
          } else {
            u5 = u8Array[idx++] & 63;
            u0 = ((u0 & 1) << 30) | (u1 << 24) | (u2 << 18) | (u3 << 12) | (u4 << 6) | u5;
          }
        }
      }
      if (u0 < 0x10000) {
        str += String.fromCharCode(u0);
      } else {
        var ch = u0 - 0x10000;
        str += String.fromCharCode(0xD800 | (ch >> 10), 0xDC00 | (ch & 0x3FF));
      }
    }
  }
}


// Given a pointer 'ptr' to a null-terminated UTF8-encoded string in the emscripten HEAP, returns