code: public String readString () {
  		if (!readVarIntFlag()) return readAsciiString(); // ASCII.
  		// Null, empty, or UTF8.
  		int charCount = readVarIntFlag(true);
  		switch (charCount) {
  		case 0:
  			return null;
  		case 1:
  			return "";
  		}
  		charCount--;
  		readUtf8Chars(charCount);
  		return new String(chars, 0, charCount);
  	}
docs: Reads the length and string of UTF8 characters, or null. This can read strings written by
  {@link Output#writeString(String)} and {@link Output#writeAscii(String)}.
  @return May be null.