Token _scanFlowScalar()

in lib/src/scanner.dart [1263:1444]
151 lines of code
52 McCabe index (conditional complexity)

  Token _scanFlowScalar({bool singleQuote = false}) {
    var start = _scanner.state;
    var buffer = StringBuffer();

    // Eat the left quote.
    _scanner.readChar();

    while (true) {
      // Check that there are no document indicators at the beginning of the
      // line.
      if (_isDocumentIndicator) {
        _scanner.error('Unexpected document indicator.');
      }

      if (_scanner.isDone) {
        throw YamlException('Unexpected end of file.', _scanner.emptySpan);
      }

      var leadingBlanks = false;
      while (!_isBlankOrEnd) {
        var char = _scanner.peekChar();
        if (singleQuote &&
            char == SINGLE_QUOTE &&
            _scanner.peekChar(1) == SINGLE_QUOTE) {
          // An escaped single quote.
          _scanner.readChar();
          _scanner.readChar();
          buffer.writeCharCode(SINGLE_QUOTE);
        } else if (char == (singleQuote ? SINGLE_QUOTE : DOUBLE_QUOTE)) {
          // The closing quote.
          break;
        } else if (!singleQuote && char == BACKSLASH && _isBreakAt(1)) {
          // An escaped newline.
          _scanner.readChar();
          _skipLine();
          leadingBlanks = true;
          break;
        } else if (!singleQuote && char == BACKSLASH) {
          var escapeStart = _scanner.state;

          // An escape sequence.
          int? codeLength;
          switch (_scanner.peekChar(1)) {
            case NUMBER_0:
              buffer.writeCharCode(NULL);
              break;
            case LETTER_A:
              buffer.writeCharCode(BELL);
              break;
            case LETTER_B:
              buffer.writeCharCode(BACKSPACE);
              break;
            case LETTER_T:
            case TAB:
              buffer.writeCharCode(TAB);
              break;
            case LETTER_N:
              buffer.writeCharCode(LF);
              break;
            case LETTER_V:
              buffer.writeCharCode(VERTICAL_TAB);
              break;
            case LETTER_F:
              buffer.writeCharCode(FORM_FEED);
              break;
            case LETTER_R:
              buffer.writeCharCode(CR);
              break;
            case LETTER_E:
              buffer.writeCharCode(ESCAPE);
              break;
            case SP:
            case DOUBLE_QUOTE:
            case SLASH:
            case BACKSLASH:
              // libyaml doesn't support an escaped forward slash, but it was
              // added in YAML 1.2. See section 5.7:
              // http://yaml.org/spec/1.2/spec.html#id2776092
              buffer.writeCharCode(_scanner.peekChar(1)!);
              break;
            case LETTER_CAP_N:
              buffer.writeCharCode(NEL);
              break;
            case UNDERSCORE:
              buffer.writeCharCode(NBSP);
              break;
            case LETTER_CAP_L:
              buffer.writeCharCode(LINE_SEPARATOR);
              break;
            case LETTER_CAP_P:
              buffer.writeCharCode(PARAGRAPH_SEPARATOR);
              break;
            case LETTER_X:
              codeLength = 2;
              break;
            case LETTER_U:
              codeLength = 4;
              break;
            case LETTER_CAP_U:
              codeLength = 8;
              break;
            default:
              throw YamlException(
                  'Unknown escape character.', _scanner.spanFrom(escapeStart));
          }

          _scanner.readChar();
          _scanner.readChar();

          if (codeLength != null) {
            var value = 0;
            for (var i = 0; i < codeLength; i++) {
              if (!_isHex) {
                _scanner.readChar();
                throw YamlException(
                    'Expected $codeLength-digit hexidecimal number.',
                    _scanner.spanFrom(escapeStart));
              }

              value = (value << 4) + _asHex(_scanner.readChar());
            }

            // Check the value and write the character.
            if ((value >= 0xD800 && value <= 0xDFFF) || value > 0x10FFFF) {
              throw YamlException('Invalid Unicode character escape code.',
                  _scanner.spanFrom(escapeStart));
            }

            buffer.writeCharCode(value);
          }
        } else {
          buffer.writeCharCode(_scanner.readChar());
        }
      }

      // Check if we're at the end of a scalar.
      if (_scanner.peekChar() == (singleQuote ? SINGLE_QUOTE : DOUBLE_QUOTE)) {
        break;
      }

      var whitespace = StringBuffer();
      var leadingBreak = '';
      var trailingBreaks = StringBuffer();
      while (_isBlank || _isBreak) {
        if (_isBlank) {
          // Consume a space or a tab.
          if (!leadingBlanks) {
            whitespace.writeCharCode(_scanner.readChar());
          } else {
            _scanner.readChar();
          }
        } else {
          // Check if it's a first line break.
          if (!leadingBlanks) {
            whitespace.clear();
            leadingBreak = _readLine();
            leadingBlanks = true;
          } else {
            trailingBreaks.write(_readLine());
          }
        }
      }

      // Join the whitespace or fold line breaks.
      if (leadingBlanks) {
        if (leadingBreak.isNotEmpty && trailingBreaks.isEmpty) {
          buffer.writeCharCode(SP);
        } else {
          buffer.write(trailingBreaks);
        }
      } else {
        buffer.write(whitespace);
        whitespace.clear();
      }
    }

    // Eat the right quote.
    _scanner.readChar();

    return ScalarToken(_scanner.spanFrom(start), buffer.toString(),
        singleQuote ? ScalarStyle.SINGLE_QUOTED : ScalarStyle.DOUBLE_QUOTED);
  }