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
16   This is available on the net from L'Ecuyer's home page,
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
36#include <string.h>
37#include <assert.h>
38#include "rand.h"
39#include "../hash.h"
40
41static inline int __seed(unsigned int x, unsigned int m)
42{
43	return (x < m) ? x + m : x;
44}
45
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
60void init_rand(struct frand_state *state)
61{
62	__init_rand(state, 1);
63}
64
65void init_rand_seed(struct frand_state *state, unsigned int seed)
66{
67	__init_rand(state, seed);
68}
69
70void __fill_random_buf(void *buf, unsigned int len, unsigned long seed)
71{
72	void *ptr = buf;
73
74	while (len) {
75		int this_len;
76
77		if (len >= sizeof(int64_t)) {
78			*((int64_t *) ptr) = seed;
79			this_len = sizeof(int64_t);
80		} else if (len >= sizeof(int32_t)) {
81			*((int32_t *) ptr) = seed;
82			this_len = sizeof(int32_t);
83		} else if (len >= sizeof(int16_t)) {
84			*((int16_t *) ptr) = seed;
85			this_len = sizeof(int16_t);
86		} else {
87			*((int8_t *) ptr) = seed;
88			this_len = sizeof(int8_t);
89		}
90		ptr += this_len;
91		len -= this_len;
92		seed *= GOLDEN_RATIO_PRIME;
93		seed >>= 3;
94	}
95}
96
97unsigned long fill_random_buf(struct frand_state *fs, void *buf,
98			      unsigned int len)
99{
100	unsigned long r = __rand(fs);
101
102	if (sizeof(int) != sizeof(long *))
103		r *= (unsigned long) __rand(fs);
104
105	__fill_random_buf(buf, len, r);
106	return r;
107}
108
109void fill_pattern(void *p, unsigned int len, char *pattern,
110		  unsigned int pattern_bytes)
111{
112	switch (pattern_bytes) {
113	case 0:
114		assert(0);
115		break;
116	case 1:
117		memset(p, pattern[0], len);
118		break;
119	default: {
120		unsigned int i = 0, size = 0;
121		unsigned char *b = p;
122
123		while (i < len) {
124			size = pattern_bytes;
125			if (size > (len - i))
126				size = len - i;
127			memcpy(b+i, pattern, size);
128			i += size;
129		}
130		break;
131		}
132	}
133}
134
135void __fill_random_buf_percentage(unsigned long seed, void *buf,
136				  unsigned int percentage,
137				  unsigned int segment, unsigned int len,
138				  char *pattern, unsigned int pbytes)
139{
140	unsigned int this_len;
141
142	if (percentage == 100) {
143		if (pbytes)
144			fill_pattern(buf, len, pattern, pbytes);
145		else
146			memset(buf, 0, len);
147		return;
148	}
149
150	if (segment > len)
151		segment = len;
152
153	while (len) {
154		/*
155		 * Fill random chunk
156		 */
157		this_len = (segment * (100 - percentage)) / 100;
158		if (this_len > len)
159			this_len = len;
160
161		__fill_random_buf(buf, this_len, seed);
162
163		len -= this_len;
164		if (!len)
165			break;
166		buf += this_len;
167
168		if (this_len > len)
169			this_len = len;
170		else if (len - this_len <= sizeof(long))
171			this_len = len;
172
173		if (pbytes)
174			fill_pattern(buf, this_len, pattern, pbytes);
175		else
176			memset(buf, 0, this_len);
177
178		len -= this_len;
179		buf += this_len;
180	}
181}
182
183unsigned long fill_random_buf_percentage(struct frand_state *fs, void *buf,
184					 unsigned int percentage,
185					 unsigned int segment, unsigned int len,
186					 char *pattern, unsigned int pbytes)
187{
188	unsigned long r = __rand(fs);
189
190	if (sizeof(int) != sizeof(long *))
191		r *= (unsigned long) __rand(fs);
192
193	__fill_random_buf_percentage(r, buf, percentage, segment, len,
194					pattern, pbytes);
195	return r;
196}
197