The value of the pos field at the time the last mark method was called.

This value is always in the range -1 through pos. If there is no marked position in the input stream, this field is -1. If there is a marked position in the input stream, then buf[markpos] is the first byte to be supplied as input after a reset operation. If markpos is not -1, then all bytes from positions buf[markpos] through buf[pos-1] must remain in the buffer array (though they may be moved to another place in the buffer array, with suitable adjustments to the values of count, pos, and markpos); they may not be discarded unless and until the difference between pos and markpos exceeds marklimit.