docs: private CharSequence parseString() throws ParseException {
          skipWhitespace();
          if (peek() != '"') {
              return null;
          }
          next();
          final int startIdx = getPosition();
  
          // Fast path
          boolean hasEscape = false;
          while (hasMore()) {
              final char c = getc();
              if (c == '\\') {
                  switch (getc()) {
                  case 'b':
                  case 'f':
                  case 'n':
                  case 'r':
                  case 't':
                  case '\'':
                  case '"':
                  case '/':
                  case '\\':
                      hasEscape = true;
                      break;
                  case 'u':
                      hasEscape = true;
                      advance(4);
                      break;
                  default:
                      throw new ParseException(this, "Invalid escape sequence: \\" + c);
                  }
              } else if (c == '"') {
                  break;
              }
          }
          final int endIdx = getPosition() - 1;
          if (!hasEscape) {
              return getSubsequence(startIdx, endIdx);
          }
  
          // Slow path (for strings with escape characters)
          setPosition(startIdx);
          final StringBuilder buf = new StringBuilder();
          while (hasMore()) {
              final char c = getc();
              if (c == '\\') {
                  switch (getc()) {
                  case 'b':
                      buf.append('\b');
                      break;
                  case 'f':
                      buf.append('\f');
                      break;
                  case 'n':
                      buf.append('\n');
                      break;
                  case 'r':
                      buf.append('\r');
                      break;
                  case 't':
                      buf.append('\t');
                      break;
                  case '\'':
                  case '"':
                  case '/':
                  case '\\':
                      buf.append(c);
                      break;
                  case 'u':
                      int charVal = 0;
                      charVal = getAndParseHexChar() << 12;
                      charVal |= getAndParseHexChar() << 8;
                      charVal |= getAndParseHexChar() << 4;
                      charVal |= getAndParseHexChar();
                      buf.append((char) charVal);
                      break;
                  default:
                      throw new ParseException(this, "Invalid escape sequence: \\" + c);
                  }
              } else if (c == '"') {
                  break;
              } else {
                  buf.append(c);
              }
          }
          skipWhitespace();
          return buf.toString();
      }