int? _decode()

in lib/src/percent/decoder.dart [188:237]
32 lines of code
8 McCabe index (conditional complexity)

int? _decode(List<int> codeUnits, int start, int end, Uint8Buffer buffer) {
  // A bitwise OR of all code units in [codeUnits]. This allows us to check for
  // out-of-range code units without adding more branches than necessary to the
  // core loop.
  var codeUnitOr = 0;

  // The beginning of the current slice of adjacent non-% characters. We can add
  // all of these to the buffer at once.
  var sliceStart = start;
  for (var i = start; i < end; i++) {
    // First, loop through non-% characters.
    var codeUnit = codeUnits[i];
    if (codeUnits[i] != $percent) {
      codeUnitOr |= codeUnit;
      continue;
    }

    // We found a %. The slice from `sliceStart` to `i` represents characters
    // than can be copied to the buffer as-is.
    if (i > sliceStart) {
      _checkForInvalidCodeUnit(codeUnitOr, codeUnits, sliceStart, i);
      buffer.addAll(codeUnits, sliceStart, i);
    }

    // Now decode the percent-encoded byte and add it as well.
    i++;
    if (i >= end) return _lastPercent;

    var firstDigit = digitForCodeUnit(codeUnits, i);
    i++;
    if (i >= end) return 16 * firstDigit;

    var secondDigit = digitForCodeUnit(codeUnits, i);
    buffer.add(16 * firstDigit + secondDigit);

    // The next iteration will look for non-% characters again.
    sliceStart = i + 1;
  }

  if (end > sliceStart) {
    _checkForInvalidCodeUnit(codeUnitOr, codeUnits, sliceStart, end);
    if (start == sliceStart) {
      buffer.addAll(codeUnits);
    } else {
      buffer.addAll(codeUnits, sliceStart, end);
    }
  }

  return null;
}