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/*
* variable.c
*
* Variable and stack related opcodes
*
*/
#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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