/* variable.c - Variable and stack related 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ #include "frotz.h"  /* * z_dec, decrement a variable. * * 	zargs[0] = variable to decrement * */void z_dec (void){    zword value;     if (zargs[0] == 0)	(*sp)--;    else if (zargs[0] < 16)	(*(fp - zargs[0]))--;    else {	zword addr = h_globals + 2 * (zargs[0] - 16);	LOW_WORD (addr, value)	value--;	SET_WORD (addr, value)    } }/* z_dec */  /* * z_dec_chk, decrement a variable and branch if now less than value. * * 	zargs[0] = variable to decrement * 	zargs[1] = value to check variable against * */void z_dec_chk (void){    zword value;     if (zargs[0] == 0)	value = --(*sp);    else if (zargs[0] < 16)	value = --(*(fp - zargs[0]));    else {	zword addr = h_globals + 2 * (zargs[0] - 16);	LOW_WORD (addr, value)	value--;	SET_WORD (addr, value)    }     branch ((short) value < (short) zargs[1]); }/* z_dec_chk */  /* * z_inc, increment a variable. * * 	zargs[0] = variable to increment * */void z_inc (void){    zword value;     if (zargs[0] == 0)	(*sp)++;    else if (zargs[0] < 16)	(*(fp - zargs[0]))++;    else {	zword addr = h_globals + 2 * (zargs[0] - 16);	LOW_WORD (addr, value)	value++;	SET_WORD (addr, value)    } }/* z_inc */  /* * z_inc_chk, increment a variable and branch if now greater than value. * * 	zargs[0] = variable to increment * 	zargs[1] = value to check variable against * */void z_inc_chk (void){    zword value;     if (zargs[0] == 0)	value = ++(*sp);    else if (zargs[0] < 16)	value = ++(*(fp - zargs[0]));    else {	zword addr = h_globals + 2 * (zargs[0] - 16);	LOW_WORD (addr, value)	value++;	SET_WORD (addr, value)    }     branch ((short) value > (short) zargs[1]); }/* z_inc_chk */  /* * z_load, store the value of a variable. * *	zargs[0] = variable to store * */void z_load (void){    zword value;     if (zargs[0] == 0)	value = *sp;    else if (zargs[0] < 16)	value = *(fp - zargs[0]);    else {	zword addr = h_globals + 2 * (zargs[0] - 16);	LOW_WORD (addr, value)    }     store (value); }/* z_load */  /* * z_pop, pop a value off the game stack and discard it. * *	no zargs used * */void z_pop (void){    sp++; }/* z_pop */  /* * z_pop_stack, pop n values off the game or user stack and discard them. * *	zargs[0] = number of values to discard *	zargs[1] = address of user stack (optional) * */void z_pop_stack (void){    if (zargc == 2) {		/* it's a user stack */ 	zword size;	zword addr = zargs[1]; 	LOW_WORD (addr, size) 	size += zargs[0];	storew (addr, size);     } else sp += zargs[0];	/* it's the game stack */ }/* z_pop_stack */  /* * z_pull, pop a value off... * * a) ...the game or a user stack and store it (V6) * *	zargs[0] = address of user stack (optional) * * b) ...the game stack and write it to a variable (other than V6) * *	zargs[0] = variable to write value to * */void z_pull (void){    zword value;     if (h_version != V6) {	/* not a V6 game, pop stack and write */ 	value = *sp++; 	if (zargs[0] == 0)	    *sp = value;	else if (zargs[0] < 16)	    *(fp - zargs[0]) = value;	else {	    zword addr = h_globals + 2 * (zargs[0] - 16);	    SET_WORD (addr, value)	}     } else {			/* it's V6, but is there a user stack? */ 	if (zargc == 1) {	/* it's a user stack */ 	    zword size;	    zword addr = zargs[0]; 	    LOW_WORD (addr, size) 	    size++;	    storew (addr, size); 	    addr += 2 * size;	    LOW_WORD (addr, value) 	} else value = *sp++;	/* it's the game stack */ 	store (value);     } }/* z_pull */  /* * z_push, push a value onto the game stack. * *	zargs[0] = value to push onto the stack * */void z_push (void){    *--sp = zargs[0]; }/* z_push */  /* * z_push_stack, push a value onto a user stack then branch if successful. * *	zargs[0] = value to push onto the stack *	zargs[1] = address of user stack * */void z_push_stack (void){    zword size;    zword addr = zargs[1];     LOW_WORD (addr, size)     if (size != 0) { 	storew ((zword) (addr + 2 * size), zargs[0]); 	size--;	storew (addr, size);     }     branch (size); }/* z_push_stack */  /* * z_store, write a value to a variable. * * 	zargs[0] = variable to be written to *      zargs[1] = value to write * */void z_store (void){    zword value = zargs[1];     if (zargs[0] == 0)	*sp = value;    else if (zargs[0] < 16)	*(fp - zargs[0]) = value;    else {	zword addr = h_globals + 2 * (zargs[0] - 16);	SET_WORD (addr, value)    } }/* z_store */