/* table.c - Table handling opcodes
 *		Copyright (c) 1995-1997 Stefan Jokisch
 *
 * This file is part of Frotz.
 *
 * Frotz is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Frotz is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */

#include "frotz.h"

/*
 * z_copy_table, copy a table or fill it with zeroes.
 *
 *		zargs[0] = address of table
 * 		zargs[1] = destination address or 0 for fill
 *		zargs[2] = size of table
 *
 * Note: Copying is safe even when source and destination overlap; but
 *       if zargs[1] is negative the table _must_ be copied forwards.
 *
 */

void z_copy_table (void)
{
    zword addr;
    zword size = zargs[2];
    zbyte value;
    int i;

    if (zargs[1] == 0)      								/* zero table */

		for (i = 0; i < size; i++)
		    storeb ((zword) (zargs[0] + i), 0);

    else if ((short) size < 0 || zargs[0] > zargs[1])		/* copy forwards */

		for (i = 0; i < (((short) size < 0) ? - (short) size : size); i++) {
		    addr = zargs[0] + i;
		    LOW_BYTE (addr, value)
		    storeb ((zword) (zargs[1] + i), value);
		}

    else												/* copy backwards */

		for (i = size - 1; i >= 0; i--) {
		    addr = zargs[0] + i;
		    LOW_BYTE (addr, value)
		    storeb ((zword) (zargs[1] + i), value);
		}

}/* z_copy_table */

/*
 * z_loadb, store a value from a table of bytes.
 *
 *		zargs[0] = address of table
 *		zargs[1] = index of table entry to store
 *
 */

void z_loadb (void)
{
    zword addr = zargs[0] + zargs[1];
    zbyte value;

    LOW_BYTE (addr, value)

    store (value);

}/* z_loadb */

/*
 * z_loadw, store a value from a table of words.
 *
 *		zargs[0] = address of table
 *		zargs[1] = index of table entry to store
 *
 */

void z_loadw (void)
{
    zword addr = zargs[0] + 2 * zargs[1];
    zword value;

    LOW_WORD (addr, value)

    store (value);

}/* z_loadw */

/*
 * z_scan_table, find and store the address of a target within a table.
 *
 *		zargs[0] = target value to be searched for
 *		zargs[1] = address of table
 *		zargs[2] = number of table entries to check value against
 *		zargs[3] = type of table (optional, defaults to 0x82)
 *
 * Note: The table is a word array if bit 7 of zargs[3] is set; otherwise
 *       it's a byte array. The lower bits hold the address step.
 *
 */

void z_scan_table (void)
{
    zword addr = zargs[1];
    int i;

    /* Supply default arguments */

    if (zargc < 4)
		zargs[3] = 0x82;

    /* Scan byte or word array */

    for (i = 0; i < zargs[2]; i++) {

		if (zargs[3] & 0x80) {		/* scan word array */

		    zword wvalue;

		    LOW_WORD (addr, wvalue)

		    if (wvalue == zargs[0])
				goto finished;

		} else {				/* scan byte array */

		    zbyte bvalue;

		    LOW_BYTE (addr, bvalue)

		    if (bvalue == zargs[0])
				goto finished;

		}

		addr += zargs[3] & 0x7f;

    }

    addr = 0;

finished:

    store (addr);
    branch (addr);

}/* z_scan_table */

/*
 * z_storeb, write a byte into a table of bytes.
 *
 *		zargs[0] = address of table
 *		zargs[1] = index of table entry
 *		zargs[2] = value to be written
 *
 */

void z_storeb (void)
{

    storeb ((zword) (zargs[0] + zargs[1]), zargs[2]);

}/* z_storeb */

/*
 * z_storew, write a word into a table of words.
 *
 *		zargs[0] = address of table
 *		zargs[1] = index of table entry
 *		zargs[2] = value to be written
 *
 */

void z_storew (void)
{

    storew ((zword) (zargs[0] + 2 * zargs[1]), zargs[2]);

}/* z_storew */
