void _parse()

in lib/src/http_headers_impl.dart [672:789]
104 lines of code
37 McCabe index (conditional complexity)

  void _parse(String s, String parameterSeparator, String valueSeparator,
      bool preserveBackslash) {
    int index = 0;

    bool done() => index == s.length;

    void skipWS() {
      while (!done()) {
        if (s[index] != " " && s[index] != "\t") return;
        index++;
      }
    }

    String parseValue() {
      int start = index;
      while (!done()) {
        if (s[index] == " " ||
            s[index] == "\t" ||
            s[index] == valueSeparator ||
            s[index] == parameterSeparator) break;
        index++;
      }
      return s.substring(start, index);
    }

    void expect(String expected) {
      if (done() || s[index] != expected) {
        throw HttpException("Failed to parse header value");
      }
      index++;
    }

    void maybeExpect(String expected) {
      if (s[index] == expected) index++;
    }

    void parseParameters() {
      var parameters = HashMap<String, String>();
      _parameters = UnmodifiableMapView(parameters);

      String parseParameterName() {
        int start = index;
        while (!done()) {
          if (s[index] == " " ||
              s[index] == "\t" ||
              s[index] == "=" ||
              s[index] == parameterSeparator ||
              s[index] == valueSeparator) break;
          index++;
        }
        return s.substring(start, index).toLowerCase();
      }

      String parseParameterValue() {
        if (!done() && s[index] == "\"") {
          // Parse quoted value.
          StringBuffer sb = StringBuffer();
          index++;
          while (!done()) {
            if (s[index] == "\\") {
              if (index + 1 == s.length) {
                throw HttpException("Failed to parse header value");
              }
              if (preserveBackslash && s[index + 1] != "\"") {
                sb.write(s[index]);
              }
              index++;
            } else if (s[index] == "\"") {
              index++;
              break;
            }
            sb.write(s[index]);
            index++;
          }
          return sb.toString();
        } else {
          // Parse non-quoted value.
          var val = parseValue();
          return val == "" ? null : val;
        }
      }

      while (!done()) {
        skipWS();
        if (done()) return;
        String name = parseParameterName();
        skipWS();
        if (done()) {
          parameters[name] = null;
          return;
        }
        maybeExpect("=");
        skipWS();
        if (done()) {
          parameters[name] = null;
          return;
        }
        String value = parseParameterValue();
        if (name == 'charset' && this is ContentTypeImpl && value != null) {
          // Charset parameter of ContentTypes are always lower-case.
          value = value.toLowerCase();
        }
        parameters[name] = value;
        skipWS();
        if (done()) return;
        // TODO: Implement support for multi-valued parameters.
        if (s[index] == valueSeparator) return;
        expect(parameterSeparator);
      }
    }

    skipWS();
    _value = parseValue();
    skipWS();
    if (done()) return;
    maybeExpect(parameterSeparator);
    parseParameters();
  }