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79c94bd3
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1/*
2 This is a maximally equidistributed combined Tausworthe generator
3 based on code from GNU Scientific Library 1.5 (30 Jun 2004)
4
5 x_n = (s1_n ^ s2_n ^ s3_n)
6
7 s1_{n+1} = (((s1_n & 4294967294) <<12) ^ (((s1_n <<13) ^ s1_n) >>19))
8 s2_{n+1} = (((s2_n & 4294967288) << 4) ^ (((s2_n << 2) ^ s2_n) >>25))
9 s3_{n+1} = (((s3_n & 4294967280) <<17) ^ (((s3_n << 3) ^ s3_n) >>11))
10
11 The period of this generator is about 2^88.
12
13 From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe
14 Generators", Mathematics of Computation, 65, 213 (1996), 203--213.
15
17
18 http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps
19 ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps
20
21 There is an erratum in the paper "Tables of Maximally
22 Equidistributed Combined LFSR Generators", Mathematics of
23 Computation, 68, 225 (1999), 261--269:
24 http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps
25
26 ... the k_j most significant bits of z_j must be non-
27 zero, for each j. (Note: this restriction also applies to the
28 computer code given in [4], but was mistakenly not mentioned in
29 that paper.)
30
31 This affects the seeding procedure by imposing the requirement
32 s1 > 1, s2 > 7, s3 > 15.
33
34*/
35
9c42684e 36#include <string.h>
d1af2894 37#include <assert.h>
1fbbf72e 38#include "rand.h"
637ef8d9 39#include "../hash.h"
1fbbf72e 40
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41static inline int __seed(unsigned int x, unsigned int m)
42{
43 return (x < m) ? x + m : x;
44}
45
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46static void __init_rand(struct frand_state *state, unsigned int seed)
47{
48 int cranks = 6;
49
50#define LCG(x, seed) ((x) * 69069 ^ (seed))
51
52 state->s1 = __seed(LCG((2^31) + (2^17) + (2^7), seed), 1);
53 state->s2 = __seed(LCG(state->s1, seed), 7);
54 state->s3 = __seed(LCG(state->s2, seed), 15);
55
56 while (cranks--)
57 __rand(state);
58}
59
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60void init_rand(struct frand_state *state)
61{
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62 __init_rand(state, 1);
63}
64
65void init_rand_seed(struct frand_state *state, unsigned int seed)
66{
67 __init_rand(state, seed);
1fbbf72e 68}
637ef8d9 69
7d9fb455 70void __fill_random_buf(void *buf, unsigned int len, unsigned long seed)
637ef8d9 71{
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72 long *ptr = buf;
73
637ef8d9 74 while ((void *) ptr - buf < len) {
7d9fb455 75 *ptr = seed;
637ef8d9 76 ptr++;
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77 seed *= GOLDEN_RATIO_PRIME;
78 seed >>= 3;
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79 }
80}
7d9fb455 81
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82unsigned long fill_random_buf(struct frand_state *fs, void *buf,
83 unsigned int len)
7d9fb455 84{
3545a109 85 unsigned long r = __rand(fs);
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86
87 if (sizeof(int) != sizeof(long *))
3545a109 88 r *= (unsigned long) __rand(fs);
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89
90 __fill_random_buf(buf, len, r);
91 return r;
92}
9c42684e 93
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94void fill_pattern(void *p, unsigned int len, char *pattern,
95 unsigned int pattern_bytes)
96{
97 switch (pattern_bytes) {
98 case 0:
99 assert(0);
100 break;
101 case 1:
102 memset(p, pattern[0], len);
103 break;
104 default: {
105 unsigned int i = 0, size = 0;
106 unsigned char *b = p;
107
108 while (i < len) {
109 size = pattern_bytes;
110 if (size > (len - i))
111 size = len - i;
112 memcpy(b+i, pattern, size);
113 i += size;
114 }
115 break;
116 }
117 }
118}
119
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120void __fill_random_buf_percentage(unsigned long seed, void *buf,
121 unsigned int percentage,
122 unsigned int segment, unsigned int len,
123 char *pattern, unsigned int pbytes)
9c42684e 124{
811ac503 125 unsigned int this_len;
9c42684e 126
811ac503 127 if (percentage == 100) {
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128 if (pbytes)
129 fill_pattern(buf, len, pattern, pbytes);
130 else
131 memset(buf, 0, len);
bc769898 132 return;
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133 }
134
135 if (segment > len)
136 segment = len;
9c42684e 137
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138 while (len) {
139 /*
140 * Fill random chunk
141 */
142 this_len = (segment * (100 - percentage)) / 100;
143 if (this_len > len)
144 this_len = len;
145
bc769898 146 __fill_random_buf(buf, this_len, seed);
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147
148 len -= this_len;
149 buf += this_len;
150
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151 if (this_len > len)
152 this_len = len;
9c42684e 153
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154 if (pbytes)
155 fill_pattern(buf, this_len, pattern, pbytes);
156 else
157 memset(buf, 0, this_len);
bc769898 158
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159 len -= this_len;
160 buf += this_len;
9c42684e 161 }
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162}
163
164unsigned long fill_random_buf_percentage(struct frand_state *fs, void *buf,
165 unsigned int percentage,
166 unsigned int segment, unsigned int len,
167 char *pattern, unsigned int pbytes)
168{
169 unsigned long r = __rand(fs);
170
171 if (sizeof(int) != sizeof(long *))
172 r *= (unsigned long) __rand(fs);
9c42684e 173
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174 __fill_random_buf_percentage(r, buf, percentage, segment, len,
175 pattern, pbytes);
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176 return r;
177}