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 * Copyright 2005, 2006 by
12 * Florian Schulze, Colin Phipps, Neil Stevens, Andrey Budko
13 *
14 * This program is free software; you can redistribute it and/or
15 * modify it under the terms of the GNU General Public License
16 * as published by the Free Software Foundation; either version 2
17 * of the License, or (at your option) any later version.
18 *
19 * This program is distributed in the hope that it will be useful,
20 * but WITHOUT ANY WARRANTY; without even the implied warranty of
21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 * GNU General Public License for more details.
23 *
24 * You should have received a copy of the GNU General Public License
25 * along with this program; if not, write to the Free Software
26 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
27 * 02111-1307, USA.
28 *
29 * DESCRIPTION:
30 * Random number LUT.
31 *
32 * 1/19/98 killough: Rewrote random number generator for better randomness,
33 * while at the same time maintaining demo sync and backward compatibility.
34 *
35 * 2/16/98 killough: Made each RNG local to each control-equivalent block,
36 * to reduce the chances of demo sync problems.
37 *
38 *-----------------------------------------------------------------------------*/
39
40
41 #include "doomstat.h"
42 #include "m_random.h"
43 #include "lprintf.h"
44
45 //
46 // M_Random
47 // Returns a 0-255 number
48 //
49 static const unsigned char rndtable[256] = { // 1/19/98 killough -- made const
50 0, 8, 109, 220, 222, 241, 149, 107, 75, 248, 254, 140, 16, 66 ,
51 74, 21, 211, 47, 80, 242, 154, 27, 205, 128, 161, 89, 77, 36 ,
52 95, 110, 85, 48, 212, 140, 211, 249, 22, 79, 200, 50, 28, 188 ,
53 52, 140, 202, 120, 68, 145, 62, 70, 184, 190, 91, 197, 152, 224 ,
54 149, 104, 25, 178, 252, 182, 202, 182, 141, 197, 4, 81, 181, 242 ,
55 145, 42, 39, 227, 156, 198, 225, 193, 219, 93, 122, 175, 249, 0 ,
56 175, 143, 70, 239, 46, 246, 163, 53, 163, 109, 168, 135, 2, 235 ,
57 25, 92, 20, 145, 138, 77, 69, 166, 78, 176, 173, 212, 166, 113 ,
58 94, 161, 41, 50, 239, 49, 111, 164, 70, 60, 2, 37, 171, 75 ,
59 136, 156, 11, 56, 42, 146, 138, 229, 73, 146, 77, 61, 98, 196 ,
60 135, 106, 63, 197, 195, 86, 96, 203, 113, 101, 170, 247, 181, 113 ,
61 80, 250, 108, 7, 255, 237, 129, 226, 79, 107, 112, 166, 103, 241 ,
62 24, 223, 239, 120, 198, 58, 60, 82, 128, 3, 184, 66, 143, 224 ,
63 145, 224, 81, 206, 163, 45, 63, 90, 168, 114, 59, 33, 159, 95 ,
64 28, 139, 123, 98, 125, 196, 15, 70, 194, 253, 54, 14, 109, 226 ,
65 71, 17, 161, 93, 186, 87, 244, 138, 20, 52, 123, 251, 26, 36 ,
66 17, 46, 52, 231, 232, 76, 31, 221, 84, 37, 216, 165, 212, 106 ,
67 197, 242, 98, 43, 39, 175, 254, 145, 190, 84, 118, 222, 187, 136 ,
68 120, 163, 236, 249
69 };
70
71 rng_t rng; // the random number state
72
73 unsigned int rngseed = 1993; // killough 3/26/98: The seed
74
75 int (P_Random)(pr_class_t pr_class
76 #ifdef INSTRUMENTED
77 , const char *file, int line
78 #endif
79 )
80 {
81 // killough 2/16/98: We always update both sets of random number
82 // generators, to ensure repeatability if the demo_compatibility
83 // flag is changed while the program is running. Changing the
84 // demo_compatibility flag does not change the sequences generated,
85 // only which one is selected from.
86 //
87 // All of this RNG stuff is tricky as far as demo sync goes --
88 // it's like playing with explosives :) Lee
89
90 #ifdef INSTRUMENTED
91 //lprintf(LO_DEBUG, "%.10d: %.10d - %s:%.5d\n", gametic, pr_class, file, line);
92 #endif
93
94 int compat = pr_class == pr_misc ?
95 (rng.prndindex = (rng.prndindex + 1) & 255) :
96 (rng. rndindex = (rng. rndindex + 1) & 255) ;
97
98 unsigned long boom;
99
100 // killough 3/31/98:
101 // If demo sync insurance is not requested, use
102 // much more unstable method by putting everything
103 // except pr_misc into pr_all_in_one
104
105 if (pr_class != pr_misc && !demo_insurance) // killough 3/31/98
106 pr_class = pr_all_in_one;
107
108 boom = rng.seed[pr_class];
109
110 // killough 3/26/98: add pr_class*2 to addend
111
112 rng.seed[pr_class] = boom * 1664525ul + 221297ul + pr_class*2;
113
114 if (demo_compatibility)
115 return rndtable[compat];
116
117 boom >>= 20;
118
119 /* killough 3/30/98: use gametic-levelstarttic to shuffle RNG
120 * killough 3/31/98: but only if demo insurance requested,
121 * since it's unnecessary for random shuffling otherwise
122 * killough 9/29/98: but use basetic now instead of levelstarttic
123 * cph - DEMOSYNC - this change makes MBF demos work,
124 * but does it break Boom ones?
125 */
126
127 if (demo_insurance)
128 boom += (gametic-basetic)*7;
129
130 return boom & 255;
131 }
132
133 // Initialize all the seeds
134 //
135 // This initialization method is critical to maintaining demo sync.
136 // Each seed is initialized according to its class, so if new classes
137 // are added they must be added to end of pr_class_t list. killough
138 //
139
M_ClearRandom(void)140 void M_ClearRandom (void)
141 {
142 int i;
143 unsigned int seed = rngseed*2+1; // add 3/26/98: add rngseed
144 for (i=0; i<NUMPRCLASS; i++) // go through each pr_class and set
145 rng.seed[i] = seed *= 69069ul; // each starting seed differently
146 rng.prndindex = rng.rndindex = 0; // clear two compatibility indices
147 }
148