apps/plugins/frotz/table.c

   1 /* table.c - Table handling 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_copy_table, copy a table or fill it with zeroes.
  25  *
  26  *      zargs[0] = address of table
  27  *      zargs[1] = destination address or 0 for fill
  28  *      zargs[2] = size of table
  29  *
  30  * Note: Copying is safe even when source and destination overlap; but
  31  *       if zargs[1] is negative the table _must_ be copied forwards.
  32  *
  33  */
  34
  35 void z_copy_table (void)
  36 {
  37     zword addr;
  38     zword size = zargs[2];
  39     zbyte value;
  40     int i;
  41
  42     if (zargs[1] == 0)                                  /* zero table */
  43
  44         for (i = 0; i < size; i++)
  45             storeb ((zword) (zargs[0] + i), 0);
  46
  47     else if ((short) size < 0 || zargs[0] > zargs[1])   /* copy forwards */
  48
  49         for (i = 0; i < (((short) size < 0) ? - (short) size : size); i++) {
  50             addr = zargs[0] + i;
  51             LOW_BYTE (addr, value)
  52             storeb ((zword) (zargs[1] + i), value);
  53         }
  54
  55     else                                                /* copy backwards */
  56
  57         for (i = size - 1; i >= 0; i--) {
  58             addr = zargs[0] + i;
  59             LOW_BYTE (addr, value)
  60             storeb ((zword) (zargs[1] + i), value);
  61         }
  62
  63 }/* z_copy_table */
  64
  65 /*
  66  * z_loadb, store a value from a table of bytes.
  67  *
  68  *      zargs[0] = address of table
  69  *      zargs[1] = index of table entry to store
  70  *
  71  */
  72
  73 void z_loadb (void)
  74 {
  75     zword addr = zargs[0] + zargs[1];
  76     zbyte value;
  77
  78     LOW_BYTE (addr, value)
  79
  80     store (value);
  81
  82 }/* z_loadb */
  83
  84 /*
  85  * z_loadw, store a value from a table of words.
  86  *
  87  *      zargs[0] = address of table
  88  *      zargs[1] = index of table entry to store
  89  *
  90  */
  91
  92 void z_loadw (void)
  93 {
  94     zword addr = zargs[0] + 2 * zargs[1];
  95     zword value;
  96
  97     LOW_WORD (addr, value)
  98
  99     store (value);
 100
 101 }/* z_loadw */
 102
 103 /*
 104  * z_scan_table, find and store the address of a target within a table.
 105  *
 106  *      zargs[0] = target value to be searched for
 107  *      zargs[1] = address of table
 108  *      zargs[2] = number of table entries to check value against
 109  *      zargs[3] = type of table (optional, defaults to 0x82)
 110  *
 111  * Note: The table is a word array if bit 7 of zargs[3] is set; otherwise
 112  *       it's a byte array. The lower bits hold the address step.
 113  *
 114  */
 115
 116 void z_scan_table (void)
 117 {
 118     zword addr = zargs[1];
 119     int i;
 120
 121     /* Supply default arguments */
 122
 123     if (zargc < 4)
 124         zargs[3] = 0x82;
 125
 126     /* Scan byte or word array */
 127
 128     for (i = 0; i < zargs[2]; i++) {
 129
 130         if (zargs[3] & 0x80) {  /* scan word array */
 131
 132             zword wvalue;
 133
 134             LOW_WORD (addr, wvalue)
 135
 136             if (wvalue == zargs[0])
 137                 goto finished;
 138
 139         } else {                /* scan byte array */
 140
 141             zbyte bvalue;
 142
 143             LOW_BYTE (addr, bvalue)
 144
 145             if (bvalue == zargs[0])
 146                 goto finished;
 147
 148         }
 149
 150         addr += zargs[3] & 0x7f;
 151
 152     }
 153
 154     addr = 0;
 155
 156 finished:
 157
 158     store (addr);
 159     branch (addr);
 160
 161 }/* z_scan_table */
 162
 163 /*
 164  * z_storeb, write a byte into a table of bytes.
 165  *
 166  *      zargs[0] = address of table
 167  *      zargs[1] = index of table entry
 168  *      zargs[2] = value to be written
 169  *
 170  */
 171
 172 void z_storeb (void)
 173 {
 174
 175     storeb ((zword) (zargs[0] + zargs[1]), zargs[2]);
 176
 177 }/* z_storeb */
 178
 179 /*
 180  * z_storew, write a word into a table of words.
 181  *
 182  *      zargs[0] = address of table
 183  *      zargs[1] = index of table entry
 184  *      zargs[2] = value to be written
 185  *
 186  */
 187
 188 void z_storew (void)
 189 {
 190
 191     storew ((zword) (zargs[0] + 2 * zargs[1]), zargs[2]);
 192
 193 }/* z_storew */