apps/plugins/frotz/variable.c

   1 /* variable.c - Variable and stack related opcodes
   2  *      Copyright (c) 1995-1997 Stefan Jokisch
   3  *
   4  * This file is part of Frotz.
   5  *
   6  * Frotz is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * Frotz is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  19  */
  20
  21 #include "frotz.h"
  22
  23 /*
  24  * z_dec, decrement a variable.
  25  *
  26  *      zargs[0] = variable to decrement
  27  *
  28  */
  29
  30 void z_dec (void)
  31 {
  32     zword value;
  33
  34     if (zargs[0] == 0)
  35         (*sp)--;
  36     else if (zargs[0] < 16)
  37         (*(fp - zargs[0]))--;
  38     else {
  39         zword addr = h_globals + 2 * (zargs[0] - 16);
  40         LOW_WORD (addr, value)
  41         value--;
  42         SET_WORD (addr, value)
  43     }
  44
  45 }/* z_dec */
  46
  47 /*
  48  * z_dec_chk, decrement a variable and branch if now less than value.
  49  *
  50  *      zargs[0] = variable to decrement
  51  *      zargs[1] = value to check variable against
  52  *
  53  */
  54
  55 void z_dec_chk (void)
  56 {
  57     zword value;
  58
  59     if (zargs[0] == 0)
  60         value = --(*sp);
  61     else if (zargs[0] < 16)
  62         value = --(*(fp - zargs[0]));
  63     else {
  64         zword addr = h_globals + 2 * (zargs[0] - 16);
  65         LOW_WORD (addr, value)
  66         value--;
  67         SET_WORD (addr, value)
  68     }
  69
  70     branch ((short) value < (short) zargs[1]);
  71
  72 }/* z_dec_chk */
  73
  74 /*
  75  * z_inc, increment a variable.
  76  *
  77  *      zargs[0] = variable to increment
  78  *
  79  */
  80
  81 void z_inc (void)
  82 {
  83     zword value;
  84
  85     if (zargs[0] == 0)
  86         (*sp)++;
  87     else if (zargs[0] < 16)
  88         (*(fp - zargs[0]))++;
  89     else {
  90         zword addr = h_globals + 2 * (zargs[0] - 16);
  91         LOW_WORD (addr, value)
  92         value++;
  93         SET_WORD (addr, value)
  94     }
  95
  96 }/* z_inc */
  97
  98 /*
  99  * z_inc_chk, increment a variable and branch if now greater than value.
 100  *
 101  *      zargs[0] = variable to increment
 102  *      zargs[1] = value to check variable against
 103  *
 104  */
 105
 106 void z_inc_chk (void)
 107 {
 108     zword value;
 109
 110     if (zargs[0] == 0)
 111         value = ++(*sp);
 112     else if (zargs[0] < 16)
 113         value = ++(*(fp - zargs[0]));
 114     else {
 115         zword addr = h_globals + 2 * (zargs[0] - 16);
 116         LOW_WORD (addr, value)
 117         value++;
 118         SET_WORD (addr, value)
 119     }
 120
 121     branch ((short) value > (short) zargs[1]);
 122
 123 }/* z_inc_chk */
 124
 125 /*
 126  * z_load, store the value of a variable.
 127  *
 128  *      zargs[0] = variable to store
 129  *
 130  */
 131
 132 void z_load (void)
 133 {
 134     zword value;
 135
 136     if (zargs[0] == 0)
 137         value = *sp;
 138     else if (zargs[0] < 16)
 139         value = *(fp - zargs[0]);
 140     else {
 141         zword addr = h_globals + 2 * (zargs[0] - 16);
 142         LOW_WORD (addr, value)
 143     }
 144
 145     store (value);
 146
 147 }/* z_load */
 148
 149 /*
 150  * z_pop, pop a value off the game stack and discard it.
 151  *
 152  *      no zargs used
 153  *
 154  */
 155
 156 void z_pop (void)
 157 {
 158
 159     sp++;
 160
 161 }/* z_pop */
 162
 163 /*
 164  * z_pop_stack, pop n values off the game or user stack and discard them.
 165  *
 166  *      zargs[0] = number of values to discard
 167  *      zargs[1] = address of user stack (optional)
 168  *
 169  */
 170
 171 void z_pop_stack (void)
 172 {
 173
 174     if (zargc == 2) {           /* it's a user stack */
 175
 176         zword size;
 177         zword addr = zargs[1];
 178
 179         LOW_WORD (addr, size)
 180
 181         size += zargs[0];
 182         storew (addr, size);
 183
 184     } else sp += zargs[0];      /* it's the game stack */
 185
 186 }/* z_pop_stack */
 187
 188 /*
 189  * z_pull, pop a value off...
 190  *
 191  * a) ...the game or a user stack and store it (V6)
 192  *
 193  *      zargs[0] = address of user stack (optional)
 194  *
 195  * b) ...the game stack and write it to a variable (other than V6)
 196  *
 197  *      zargs[0] = variable to write value to
 198  *
 199  */
 200
 201 void z_pull (void)
 202 {
 203     zword value;
 204
 205     if (h_version != V6) {      /* not a V6 game, pop stack and write */
 206
 207         value = *sp++;
 208
 209         if (zargs[0] == 0)
 210             *sp = value;
 211         else if (zargs[0] < 16)
 212             *(fp - zargs[0]) = value;
 213         else {
 214             zword addr = h_globals + 2 * (zargs[0] - 16);
 215             SET_WORD (addr, value)
 216         }
 217
 218     } else {                    /* it's V6, but is there a user stack? */
 219
 220         if (zargc == 1) {       /* it's a user stack */
 221
 222             zword size;
 223             zword addr = zargs[0];
 224
 225             LOW_WORD (addr, size)
 226
 227             size++;
 228             storew (addr, size);
 229
 230             addr += 2 * size;
 231             LOW_WORD (addr, value)
 232
 233         } else value = *sp++;   /* it's the game stack */
 234
 235         store (value);
 236
 237     }
 238
 239 }/* z_pull */
 240
 241 /*
 242  * z_push, push a value onto the game stack.
 243  *
 244  *      zargs[0] = value to push onto the stack
 245  *
 246  */
 247
 248 void z_push (void)
 249 {
 250
 251     *--sp = zargs[0];
 252
 253 }/* z_push */
 254
 255 /*
 256  * z_push_stack, push a value onto a user stack then branch if successful.
 257  *
 258  *      zargs[0] = value to push onto the stack
 259  *      zargs[1] = address of user stack
 260  *
 261  */
 262
 263 void z_push_stack (void)
 264 {
 265     zword size;
 266     zword addr = zargs[1];
 267
 268     LOW_WORD (addr, size)
 269
 270     if (size != 0) {
 271
 272         storew ((zword) (addr + 2 * size), zargs[0]);
 273
 274         size--;
 275         storew (addr, size);
 276
 277     }
 278
 279     branch (size);
 280
 281 }/* z_push_stack */
 282
 283 /*
 284  * z_store, write a value to a variable.
 285  *
 286  *      zargs[0] = variable to be written to
 287  *      zargs[1] = value to write
 288  *
 289  */
 290
 291 void z_store (void)
 292 {
 293     zword value = zargs[1];
 294
 295     if (zargs[0] == 0)
 296         *sp = value;
 297     else if (zargs[0] < 16)
 298         *(fp - zargs[0]) = value;
 299     else {
 300         zword addr = h_globals + 2 * (zargs[0] - 16);
 301         SET_WORD (addr, value)
 302     }
 303
 304 }/* z_store */