#include <stdio.h>

int
ungetc(c, iop)
int	c;
register FILE *iop;
{
	if(c == EOF)
		return(-1);
	if((iop->_flag & _IOREAD) == 0 || iop->_ptr <= iop->_base)
		if(iop->_ptr == iop->_base && iop->_cnt == 0)
			++iop->_ptr;
		else
			return(-1);
	*--iop->_ptr = c;
	++iop->_cnt;
	return(c);
}