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Diffstat (limited to 'apps/plugins/frotz/random.c')
-rw-r--r-- | apps/plugins/frotz/random.c | 82 |
1 files changed, 82 insertions, 0 deletions
diff --git a/apps/plugins/frotz/random.c b/apps/plugins/frotz/random.c new file mode 100644 index 0000000000..6ea14d89c9 --- /dev/null +++ b/apps/plugins/frotz/random.c | |||
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1 | /* random.c - Z-machine random number generator | ||
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 | static long A = 1; | ||
24 | |||
25 | static int interval = 0; | ||
26 | static int counter = 0; | ||
27 | |||
28 | /* | ||
29 | * seed_random | ||
30 | * | ||
31 | * Set the seed value for the random number generator. | ||
32 | * | ||
33 | */ | ||
34 | |||
35 | void seed_random (int value) | ||
36 | { | ||
37 | |||
38 | if (value == 0) { /* ask interface for seed value */ | ||
39 | A = os_random_seed (); | ||
40 | interval = 0; | ||
41 | } else if (value < 1000) { /* special seed value */ | ||
42 | counter = 0; | ||
43 | interval = value; | ||
44 | } else { /* standard seed value */ | ||
45 | A = value; | ||
46 | interval = 0; | ||
47 | } | ||
48 | |||
49 | }/* seed_random */ | ||
50 | |||
51 | /* | ||
52 | * z_random, store a random number or set the random number seed. | ||
53 | * | ||
54 | * zargs[0] = range (positive) or seed value (negative) | ||
55 | * | ||
56 | */ | ||
57 | |||
58 | void z_random () | ||
59 | { | ||
60 | |||
61 | if ((short) zargs[0] <= 0) { /* set random seed */ | ||
62 | |||
63 | seed_random (- (short) zargs[0]); | ||
64 | store (0); | ||
65 | |||
66 | } else { /* generate random number */ | ||
67 | |||
68 | zword result; | ||
69 | |||
70 | if (interval != 0) { /* ...in special mode */ | ||
71 | result = counter++; | ||
72 | if (counter == interval) counter = 0; | ||
73 | } else { /* ...in standard mode */ | ||
74 | A = 0x015a4e35L * A + 1; | ||
75 | result = (A >> 16) & 0x7fff; | ||
76 | } | ||
77 | |||
78 | store ((zword) (result % zargs[0] + 1)); | ||
79 | |||
80 | } | ||
81 | |||
82 | }/* z_random */ | ||