--- /dev/null
+/* 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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 */
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