apps/plugins/doom/m_random.c

   1 /* Emacs style mode select   -*- C++ -*-
   2  *-----------------------------------------------------------------------------
   3  *
   4  *
   5  *  PrBoom a Doom port merged with LxDoom and LSDLDoom
   6  *  based on BOOM, a modified and improved DOOM engine
   7  *  Copyright (C) 1999 by
   8  *  id Software, Chi Hoang, Lee Killough, Jim Flynn, Rand Phares, Ty Halderman
   9  *  Copyright (C) 1999-2000 by
  10  *  Jess Haas, Nicolas Kalkhof, Colin Phipps, Florian Schulze
  11  *
  12  *  This program is free software; you can redistribute it and/or
  13  *  modify it under the terms of the GNU General Public License
  14  *  as published by the Free Software Foundation; either version 2
  15  *  of the License, or (at your option) any later version.
  16  *
  17  *  This program is distributed in the hope that it will be useful,
  18  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  *  GNU General Public License for more details.
  21  *
  22  *  You should have received a copy of the GNU General Public License
  23  *  along with this program; if not, write to the Free Software
  24  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  25  *  02111-1307, USA.
  26  *
  27  * DESCRIPTION:
  28  *      Random number LUT.
  29  *
  30  * 1/19/98 killough: Rewrote random number generator for better randomness,
  31  * while at the same time maintaining demo sync and backward compatibility.
  32  *
  33  * 2/16/98 killough: Made each RNG local to each control-equivalent block,
  34  * to reduce the chances of demo sync problems.
  35  *
  36  *-----------------------------------------------------------------------------*/
  37
  38
  39 #include "doomstat.h"
  40 #include "m_random.h"
  41
  42 //
  43 // M_Random
  44 // Returns a 0-255 number
  45 //
  46 static const unsigned char rndtable[256] = { // 1/19/98 killough -- made const
  47          0,   8, 109, 220, 222, 241, 149, 107,  75, 248, 254, 140,  16,  66 ,
  48          74,  21, 211,  47,  80, 242, 154,  27, 205, 128, 161,  89,  77,  36 ,
  49          95, 110,  85,  48, 212, 140, 211, 249,  22,  79, 200,  50,  28, 188 ,
  50          52, 140, 202, 120,  68, 145,  62,  70, 184, 190,  91, 197, 152, 224 ,
  51          149, 104,  25, 178, 252, 182, 202, 182, 141, 197,   4,  81, 181, 242 ,
  52          145,  42,  39, 227, 156, 198, 225, 193, 219,  93, 122, 175, 249,   0 ,
  53          175, 143,  70, 239,  46, 246, 163,  53, 163, 109, 168, 135,   2, 235 ,
  54          25,  92,  20, 145, 138,  77,  69, 166,  78, 176, 173, 212, 166, 113 ,
  55          94, 161,  41,  50, 239,  49, 111, 164,  70,  60,   2,  37, 171,  75 ,
  56          136, 156,  11,  56,  42, 146, 138, 229,  73, 146,  77,  61,  98, 196 ,
  57          135, 106,  63, 197, 195,  86,  96, 203, 113, 101, 170, 247, 181, 113 ,
  58          80, 250, 108,   7, 255, 237, 129, 226,  79, 107, 112, 166, 103, 241 ,
  59          24, 223, 239, 120, 198,  58,  60,  82, 128,   3, 184,  66, 143, 224 ,
  60          145, 224,  81, 206, 163,  45,  63,  90, 168, 114,  59,  33, 159,  95 ,
  61          28, 139, 123,  98, 125, 196,  15,  70, 194, 253,  54,  14, 109, 226 ,
  62          71,  17, 161,  93, 186,  87, 244, 138,  20,  52, 123, 251,  26,  36 ,
  63          17,  46,  52, 231, 232,  76,  31, 221,  84,  37, 216, 165, 212, 106 ,
  64          197, 242,  98,  43,  39, 175, 254, 145, 190,  84, 118, 222, 187, 136 ,
  65          120, 163, 236, 249
  66       };
  67
  68 rng_t rng;     // the random number state
  69
  70 unsigned long rngseed = 1993;   // killough 3/26/98: The seed
  71
  72 int P_Random(pr_class_t pr_class)
  73 {
  74    // killough 2/16/98:  We always update both sets of random number
  75    // generators, to ensure repeatability if the demo_compatibility
  76    // flag is changed while the program is running. Changing the
  77    // demo_compatibility flag does not change the sequences generated,
  78    // only which one is selected from.
  79    //
  80    // All of this RNG stuff is tricky as far as demo sync goes --
  81    // it's like playing with explosives :) Lee
  82
  83    int compat = pr_class == pr_misc ?
  84                 (rng.prndindex = (rng.prndindex + 1) & 255) :
  85                 (rng. rndindex = (rng. rndindex + 1) & 255) ;
  86
  87    unsigned long boom;
  88
  89    // killough 3/31/98:
  90    // If demo sync insurance is not requested, use
  91    // much more unstable method by putting everything
  92    // except pr_misc into pr_all_in_one
  93
  94    if (pr_class != pr_misc && !demo_insurance)      // killough 3/31/98
  95       pr_class = pr_all_in_one;
  96
  97    boom = rng.seed[pr_class];
  98
  99    // killough 3/26/98: add pr_class*2 to addend
 100
 101    rng.seed[pr_class] = boom * 1664525ul + 221297ul + pr_class*2;
 102
 103    if (demo_compatibility)
 104       return rndtable[compat];
 105
 106    boom >>= 20;
 107
 108    /* killough 3/30/98: use gametic-levelstarttic to shuffle RNG
 109     * killough 3/31/98: but only if demo insurance requested,
 110     * since it's unnecessary for random shuffling otherwise
 111     * killough 9/29/98: but use basetic now instead of levelstarttic
 112     * cph - DEMOSYNC - this change makes MBF demos work,
 113     *       but does it break Boom ones?
 114     */
 115
 116    if (demo_insurance)
 117       boom += (gametic-basetic)*7;
 118
 119    return boom & 255;
 120 }
 121
 122 // Initialize all the seeds
 123 //
 124 // This initialization method is critical to maintaining demo sync.
 125 // Each seed is initialized according to its class, so if new classes
 126 // are added they must be added to end of pr_class_t list. killough
 127 //
 128
 129 void M_ClearRandom (void)
 130 {
 131    int i;
 132    unsigned long seed = rngseed*2+1;    // add 3/26/98: add rngseed
 133    for (i=0; i<NUMPRCLASS; i++)         // go through each pr_class and set
 134       rng.seed[i] = seed *= 69069ul;     // each starting seed differently
 135    rng.prndindex = rng.rndindex = 0;    // clear two compatibility indices
 136 }