projects / unix-history / blame
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1 | /* |
| 2 | * Copyright (c) 1988 The Regents of the University of California. | |
| 3 | * All rights reserved. | |
| 4 | * | |
| 5 | * This code is derived from software contributed to Berkeley by | |
| 6 | * Timothy C. Stoehr. | |
| 7 | * | |
| b2e7427f | 8 | * %sccs.include.redist.c% |
| fc3e88fd KB |
9 | */ |
| 10 | ||
| b3afadef | 11 | #ifndef lint |
| b2e7427f | 12 | static char sccsid[] = "@(#)random.c 5.3 (Berkeley) %G%"; |
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13 | #endif /* not lint */ |
| 14 | ||
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15 | /* |
| 16 | * random.c | |
| 17 | * | |
| 18 | * This source herein may be modified and/or distributed by anybody who | |
| 19 | * so desires, with the following restrictions: | |
| 20 | * 1.) No portion of this notice shall be removed. | |
| 21 | * 2.) Credit shall not be taken for the creation of this source. | |
| 22 | * 3.) This code is not to be traded, sold, or used for personal | |
| 23 | * gain or profit. | |
| 24 | * | |
| 25 | */ | |
| 26 | ||
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27 | static long rntb[32] = { |
| 28 | 3, 0x9a319039, 0x32d9c024, 0x9b663182, 0x5da1f342, | |
| 29 | 0xde3b81e0, 0xdf0a6fb5, 0xf103bc02, 0x48f340fb, 0x7449e56b, | |
| 30 | 0xbeb1dbb0, 0xab5c5918, 0x946554fd, 0x8c2e680f, 0xeb3d799f, | |
| 31 | 0xb11ee0b7, 0x2d436b86, 0xda672e2a, 0x1588ca88, 0xe369735d, | |
| 32 | 0x904f35f7, 0xd7158fd6, 0x6fa6f051, 0x616e6b96, 0xac94efdc, | |
| 33 | 0x36413f93, 0xc622c298, 0xf5a42ab8, 0x8a88d77b, 0xf5ad9d0e, | |
| 34 | 0x8999220b, 0x27fb47b9 | |
| 35 | }; | |
| 36 | ||
| 37 | static long *fptr = &rntb[4]; | |
| 38 | static long *rptr = &rntb[1]; | |
| 39 | static long *state = &rntb[1]; | |
| 40 | static int rand_type = 3; | |
| 41 | static int rand_deg = 31; | |
| 42 | static int rand_sep = 3; | |
| 43 | static long *end_ptr = &rntb[32]; | |
| 44 | ||
| 45 | srrandom(x) | |
| 46 | int x; | |
| 47 | { | |
| 48 | register int i; | |
| 49 | long rrandom(); | |
| 50 | ||
| 51 | state[0] = (long) x; | |
| 52 | if (rand_type != 0) { | |
| 53 | for (i = 1; i < rand_deg; i++) { | |
| 54 | state[i] = 1103515245 * state[i - 1] + 12345; | |
| 55 | } | |
| 56 | fptr = &state[rand_sep]; | |
| 57 | rptr = &state[0]; | |
| 58 | for (i = 0; i < 10 * rand_deg; i++) { | |
| 59 | (void) rrandom(); | |
| 60 | } | |
| 61 | } | |
| 62 | } | |
| 63 | ||
| 64 | long | |
| 65 | rrandom() | |
| 66 | { | |
| 67 | long i; | |
| 68 | ||
| 69 | if (rand_type == 0) { | |
| 70 | i = state[0] = (state[0]*1103515245 + 12345) & 0x7fffffff; | |
| 71 | } else { | |
| 72 | *fptr += *rptr; | |
| 73 | i = (*fptr >> 1) & 0x7fffffff; | |
| 74 | if (++fptr >= end_ptr) { | |
| 75 | fptr = state; | |
| 76 | ++rptr; | |
| 77 | } else { | |
| 78 | if (++rptr >= end_ptr) { | |
| 79 | rptr = state; | |
| 80 | } | |
| 81 | } | |
| 82 | } | |
| 83 | return(i); | |
| 84 | } | |
| 85 | ||
| 86 | get_rand(x, y) | |
| 87 | register int x, y; | |
| 88 | { | |
| 89 | register int r, t; | |
| 90 | long lr; | |
| 91 | ||
| 92 | if (x > y) { | |
| 93 | t = y; | |
| 94 | y = x; | |
| 95 | x = t; | |
| 96 | } | |
| 97 | lr = rrandom(); | |
| 98 | lr &= (long) 0x00003fff; | |
| 99 | r = (int) lr; | |
| 100 | r = (r % ((y - x) + 1)) + x; | |
| 101 | return(r); | |
| 102 | } | |
| 103 | ||
| 104 | rand_percent(percentage) | |
| 105 | register int percentage; | |
| 106 | { | |
| 107 | return(get_rand(1, 100) <= percentage); | |
| 108 | } | |
| 109 | ||
| 110 | coin_toss() | |
| 111 | { | |
| 112 | ||
| 113 | return(((rrandom() & 01) ? 1 : 0)); | |
| 114 | } |