1 | /*␊ |
2 | * Copyright (c) 1983, 1993␊ |
3 | *␉The Regents of the University of California. All rights reserved.␊ |
4 | *␊ |
5 | * Redistribution and use in source and binary forms, with or without␊ |
6 | * modification, are permitted provided that the following conditions␊ |
7 | * are met:␊ |
8 | * 1. Redistributions of source code must retain the above copyright␊ |
9 | * notice, this list of conditions and the following disclaimer.␊ |
10 | * 2. Redistributions in binary form must reproduce the above copyright␊ |
11 | * notice, this list of conditions and the following disclaimer in the␊ |
12 | * documentation and/or other materials provided with the distribution.␊ |
13 | * 4. Neither the name of the University nor the names of its contributors␊ |
14 | * may be used to endorse or promote products derived from this software␊ |
15 | * without specific prior written permission.␊ |
16 | *␊ |
17 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND␊ |
18 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE␊ |
19 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE␊ |
20 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE␊ |
21 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL␊ |
22 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS␊ |
23 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)␊ |
24 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT␊ |
25 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY␊ |
26 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF␊ |
27 | * SUCH DAMAGE.␊ |
28 | */␊ |
29 | ␊ |
30 | #if defined(LIBC_SCCS) && !defined(lint)␊ |
31 | static char sccsid[] = "@(#)random.c␉8.2 (Berkeley) 5/19/95";␊ |
32 | #endif /* LIBC_SCCS and not lint */␊ |
33 | #include <sys/cdefs.h>␊ |
34 | __FBSDID("$FreeBSD: src/lib/libc/stdlib/random.c,v 1.25 2007/01/09 00:28:10 imp Exp $");␊ |
35 | ␊ |
36 | /*␊ |
37 | * We always compile with __DARWIN_UNIX03 set to one, relying on the fact that␊ |
38 | * (for non-LP64) sizeof(int) == sizeof(long) == sizeof(size_t), so that we␊ |
39 | * don't have to have two different versions of the prototypes. For LP64,␊ |
40 | * we only support the POSIX-compatible prototypes.␊ |
41 | */␊ |
42 | #undef ␉__DARWIN_UNIX03␊ |
43 | #define␉__DARWIN_UNIX03␉1␊ |
44 | #include "namespace.h"␊ |
45 | #include <sys/time.h> /* for srandomdev() */␊ |
46 | #include <fcntl.h> /* for srandomdev() */␊ |
47 | #include <stdint.h>␊ |
48 | #include <stdio.h>␊ |
49 | #include <stdlib.h>␊ |
50 | #include <unistd.h> /* for srandomdev() */␊ |
51 | #include "un-namespace.h"␊ |
52 | ␊ |
53 | /*␊ |
54 | * random.c:␊ |
55 | *␊ |
56 | * An improved random number generation package. In addition to the standard␊ |
57 | * rand()/srand() like interface, this package also has a special state info␊ |
58 | * interface. The initstate() routine is called with a seed, an array of␊ |
59 | * bytes, and a count of how many bytes are being passed in; this array is␊ |
60 | * then initialized to contain information for random number generation with␊ |
61 | * that much state information. Good sizes for the amount of state␊ |
62 | * information are 32, 64, 128, and 256 bytes. The state can be switched by␊ |
63 | * calling the setstate() routine with the same array as was initiallized␊ |
64 | * with initstate(). By default, the package runs with 128 bytes of state␊ |
65 | * information and generates far better random numbers than a linear␊ |
66 | * congruential generator. If the amount of state information is less than␊ |
67 | * 32 bytes, a simple linear congruential R.N.G. is used.␊ |
68 | *␊ |
69 | * Internally, the state information is treated as an array of uint32_t's; the␊ |
70 | * zeroeth element of the array is the type of R.N.G. being used (small␊ |
71 | * integer); the remainder of the array is the state information for the␊ |
72 | * R.N.G. Thus, 32 bytes of state information will give 7 ints worth of␊ |
73 | * state information, which will allow a degree seven polynomial. (Note:␊ |
74 | * the zeroeth word of state information also has some other information␊ |
75 | * stored in it -- see setstate() for details).␊ |
76 | *␊ |
77 | * The random number generation technique is a linear feedback shift register␊ |
78 | * approach, employing trinomials (since there are fewer terms to sum up that␊ |
79 | * way). In this approach, the least significant bit of all the numbers in␊ |
80 | * the state table will act as a linear feedback shift register, and will␊ |
81 | * have period 2^deg - 1 (where deg is the degree of the polynomial being␊ |
82 | * used, assuming that the polynomial is irreducible and primitive). The␊ |
83 | * higher order bits will have longer periods, since their values are also␊ |
84 | * influenced by pseudo-random carries out of the lower bits. The total␊ |
85 | * period of the generator is approximately deg*(2**deg - 1); thus doubling␊ |
86 | * the amount of state information has a vast influence on the period of the␊ |
87 | * generator. Note: the deg*(2**deg - 1) is an approximation only good for␊ |
88 | * large deg, when the period of the shift is the dominant factor.␊ |
89 | * With deg equal to seven, the period is actually much longer than the␊ |
90 | * 7*(2**7 - 1) predicted by this formula.␊ |
91 | *␊ |
92 | * Modified 28 December 1994 by Jacob S. Rosenberg.␊ |
93 | * The following changes have been made:␊ |
94 | * All references to the type u_int have been changed to unsigned long.␊ |
95 | * All references to type int have been changed to type long. Other␊ |
96 | * cleanups have been made as well. A warning for both initstate and␊ |
97 | * setstate has been inserted to the effect that on Sparc platforms␊ |
98 | * the 'arg_state' variable must be forced to begin on word boundaries.␊ |
99 | * This can be easily done by casting a long integer array to char *.␊ |
100 | * The overall logic has been left STRICTLY alone. This software was␊ |
101 | * tested on both a VAX and Sun SpacsStation with exactly the same␊ |
102 | * results. The new version and the original give IDENTICAL results.␊ |
103 | * The new version is somewhat faster than the original. As the␊ |
104 | * documentation says: "By default, the package runs with 128 bytes of␊ |
105 | * state information and generates far better random numbers than a linear␊ |
106 | * congruential generator. If the amount of state information is less than␊ |
107 | * 32 bytes, a simple linear congruential R.N.G. is used." For a buffer of␊ |
108 | * 128 bytes, this new version runs about 19 percent faster and for a 16␊ |
109 | * byte buffer it is about 5 percent faster.␊ |
110 | */␊ |
111 | ␊ |
112 | /*␊ |
113 | * For each of the currently supported random number generators, we have a␊ |
114 | * break value on the amount of state information (you need at least this␊ |
115 | * many bytes of state info to support this random number generator), a degree␊ |
116 | * for the polynomial (actually a trinomial) that the R.N.G. is based on, and␊ |
117 | * the separation between the two lower order coefficients of the trinomial.␊ |
118 | */␊ |
119 | #define␉TYPE_0␉␉0␉␉/* linear congruential */␊ |
120 | #define␉BREAK_0␉␉8␊ |
121 | #define␉DEG_0␉␉0␊ |
122 | #define␉SEP_0␉␉0␊ |
123 | ␊ |
124 | #define␉TYPE_1␉␉1␉␉/* x**7 + x**3 + 1 */␊ |
125 | #define␉BREAK_1␉␉32␊ |
126 | #define␉DEG_1␉␉7␊ |
127 | #define␉SEP_1␉␉3␊ |
128 | ␊ |
129 | #define␉TYPE_2␉␉2␉␉/* x**15 + x + 1 */␊ |
130 | #define␉BREAK_2␉␉64␊ |
131 | #define␉DEG_2␉␉15␊ |
132 | #define␉SEP_2␉␉1␊ |
133 | ␊ |
134 | #define␉TYPE_3␉␉3␉␉/* x**31 + x**3 + 1 */␊ |
135 | #define␉BREAK_3␉␉128␊ |
136 | #define␉DEG_3␉␉31␊ |
137 | #define␉SEP_3␉␉3␊ |
138 | ␊ |
139 | #define␉TYPE_4␉␉4␉␉/* x**63 + x + 1 */␊ |
140 | #define␉BREAK_4␉␉256␊ |
141 | #define␉DEG_4␉␉63␊ |
142 | #define␉SEP_4␉␉1␊ |
143 | ␊ |
144 | /*␊ |
145 | * Array versions of the above information to make code run faster --␊ |
146 | * relies on fact that TYPE_i == i.␊ |
147 | */␊ |
148 | #define␉MAX_TYPES␉5␉␉/* max number of types above */␊ |
149 | ␊ |
150 | #ifdef USE_WEAK_SEEDING␊ |
151 | #define NSHUFF 0␊ |
152 | #else /* !USE_WEAK_SEEDING */␊ |
153 | #define NSHUFF 50 /* to drop some "seed -> 1st value" linearity */␊ |
154 | #endif /* !USE_WEAK_SEEDING */␊ |
155 | ␊ |
156 | static const int degrees[MAX_TYPES] =␉{ DEG_0, DEG_1, DEG_2, DEG_3, DEG_4 };␊ |
157 | static const int seps [MAX_TYPES] =␉{ SEP_0, SEP_1, SEP_2, SEP_3, SEP_4 };␊ |
158 | ␊ |
159 | /*␊ |
160 | * Initially, everything is set up as if from:␊ |
161 | *␊ |
162 | *␉initstate(1, randtbl, 128);␊ |
163 | *␊ |
164 | * Note that this initialization takes advantage of the fact that srandom()␊ |
165 | * advances the front and rear pointers 10*rand_deg times, and hence the␊ |
166 | * rear pointer which starts at 0 will also end up at zero; thus the zeroeth␊ |
167 | * element of the state information, which contains info about the current␊ |
168 | * position of the rear pointer is just␊ |
169 | *␊ |
170 | *␉MAX_TYPES * (rptr - state) + TYPE_3 == TYPE_3.␊ |
171 | */␊ |
172 | ␊ |
173 | static uint32_t randtbl[DEG_3 + 1] = {␊ |
174 | ␉TYPE_3,␊ |
175 | #ifdef USE_WEAK_SEEDING␊ |
176 | /* Historic implementation compatibility */␊ |
177 | /* The random sequences do not vary much with the seed */␊ |
178 | ␉0x9a319039, 0x32d9c024, 0x9b663182, 0x5da1f342, 0xde3b81e0, 0xdf0a6fb5,␊ |
179 | ␉0xf103bc02, 0x48f340fb, 0x7449e56b, 0xbeb1dbb0, 0xab5c5918, 0x946554fd,␊ |
180 | ␉0x8c2e680f, 0xeb3d799f, 0xb11ee0b7, 0x2d436b86, 0xda672e2a, 0x1588ca88,␊ |
181 | ␉0xe369735d, 0x904f35f7, 0xd7158fd6, 0x6fa6f051, 0x616e6b96, 0xac94efdc,␊ |
182 | ␉0x36413f93, 0xc622c298, 0xf5a42ab8, 0x8a88d77b, 0xf5ad9d0e, 0x8999220b,␊ |
183 | ␉0x27fb47b9,␊ |
184 | #else /* !USE_WEAK_SEEDING */␊ |
185 | ␉0x991539b1, 0x16a5bce3, 0x6774a4cd, 0x3e01511e, 0x4e508aaa, 0x61048c05,␊ |
186 | ␉0xf5500617, 0x846b7115, 0x6a19892c, 0x896a97af, 0xdb48f936, 0x14898454,␊ |
187 | ␉0x37ffd106, 0xb58bff9c, 0x59e17104, 0xcf918a49, 0x09378c83, 0x52c7a471,␊ |
188 | ␉0x8d293ea9, 0x1f4fc301, 0xc3db71be, 0x39b44e1c, 0xf8a44ef9, 0x4c8b80b1,␊ |
189 | ␉0x19edc328, 0x87bf4bdd, 0xc9b240e5, 0xe9ee4b1b, 0x4382aee7, 0x535b6b41,␊ |
190 | ␉0xf3bec5da␊ |
191 | #endif /* !USE_WEAK_SEEDING */␊ |
192 | };␊ |
193 | ␊ |
194 | /*␊ |
195 | * fptr and rptr are two pointers into the state info, a front and a rear␊ |
196 | * pointer. These two pointers are always rand_sep places aparts, as they␊ |
197 | * cycle cyclically through the state information. (Yes, this does mean we␊ |
198 | * could get away with just one pointer, but the code for random() is more␊ |
199 | * efficient this way). The pointers are left positioned as they would be␊ |
200 | * from the call␊ |
201 | *␊ |
202 | *␉initstate(1, randtbl, 128);␊ |
203 | *␊ |
204 | * (The position of the rear pointer, rptr, is really 0 (as explained above␊ |
205 | * in the initialization of randtbl) because the state table pointer is set␊ |
206 | * to point to randtbl[1] (as explained below).␊ |
207 | */␊ |
208 | static uint32_t *fptr = &randtbl[SEP_3 + 1];␊ |
209 | static uint32_t *rptr = &randtbl[1];␊ |
210 | ␊ |
211 | /*␊ |
212 | * The following things are the pointer to the state information table, the␊ |
213 | * type of the current generator, the degree of the current polynomial being␊ |
214 | * used, and the separation between the two pointers. Note that for efficiency␊ |
215 | * of random(), we remember the first location of the state information, not␊ |
216 | * the zeroeth. Hence it is valid to access state[-1], which is used to␊ |
217 | * store the type of the R.N.G. Also, we remember the last location, since␊ |
218 | * this is more efficient than indexing every time to find the address of␊ |
219 | * the last element to see if the front and rear pointers have wrapped.␊ |
220 | */␊ |
221 | static uint32_t *state = &randtbl[1];␊ |
222 | static int rand_type = TYPE_3;␊ |
223 | static int rand_deg = DEG_3;␊ |
224 | static int rand_sep = SEP_3;␊ |
225 | static uint32_t *end_ptr = &randtbl[DEG_3 + 1];␊ |
226 | ␊ |
227 | static inline uint32_t good_rand(int32_t) __attribute__((always_inline));␊ |
228 | ␊ |
229 | static inline uint32_t good_rand (x)␊ |
230 | int32_t x;␊ |
231 | {␊ |
232 | #ifdef USE_WEAK_SEEDING␊ |
233 | /*␊ |
234 | * Historic implementation compatibility.␊ |
235 | * The random sequences do not vary much with the seed,␊ |
236 | * even with overflowing.␊ |
237 | */␊ |
238 | ␉return (1103515245 * x + 12345);␊ |
239 | #else /* !USE_WEAK_SEEDING */␊ |
240 | /*␊ |
241 | * Compute x = (7^5 * x) mod (2^31 - 1)␊ |
242 | * wihout overflowing 31 bits:␊ |
243 | * (2^31 - 1) = 127773 * (7^5) + 2836␊ |
244 | * From "Random number generators: good ones are hard to find",␊ |
245 | * Park and Miller, Communications of the ACM, vol. 31, no. 10,␊ |
246 | * October 1988, p. 1195.␊ |
247 | */␊ |
248 | ␉int32_t hi, lo;␊ |
249 | ␊ |
250 | ␉/* Can't be initialized with 0, so use another value. */␊ |
251 | ␉if (x == 0)␊ |
252 | ␉␉x = 123459876;␊ |
253 | ␉hi = x / 127773;␊ |
254 | ␉lo = x % 127773;␊ |
255 | ␉x = 16807 * lo - 2836 * hi;␊ |
256 | ␉if (x < 0)␊ |
257 | ␉␉x += 0x7fffffff;␊ |
258 | ␉return (x);␊ |
259 | #endif /* !USE_WEAK_SEEDING */␊ |
260 | }␊ |
261 | ␊ |
262 | /*␊ |
263 | * srandom:␊ |
264 | *␊ |
265 | * Initialize the random number generator based on the given seed. If the␊ |
266 | * type is the trivial no-state-information type, just remember the seed.␊ |
267 | * Otherwise, initializes state[] based on the given "seed" via a linear␊ |
268 | * congruential generator. Then, the pointers are set to known locations␊ |
269 | * that are exactly rand_sep places apart. Lastly, it cycles the state␊ |
270 | * information a given number of times to get rid of any initial dependencies␊ |
271 | * introduced by the L.C.R.N.G. Note that the initialization of randtbl[]␊ |
272 | * for default usage relies on values produced by this routine.␊ |
273 | */␊ |
274 | void␊ |
275 | srandom(x)␊ |
276 | unsigned x;␊ |
277 | {␊ |
278 | ␉int i, lim;␊ |
279 | ␊ |
280 | ␉state[0] = (uint32_t)x;␊ |
281 | ␉if (rand_type == TYPE_0)␊ |
282 | ␉␉lim = NSHUFF;␊ |
283 | ␉else {␊ |
284 | ␉␉for (i = 1; i < rand_deg; i++)␊ |
285 | ␉␉␉state[i] = good_rand(state[i - 1]);␊ |
286 | ␉␉fptr = &state[rand_sep];␊ |
287 | ␉␉rptr = &state[0];␊ |
288 | ␉␉lim = 10 * rand_deg;␊ |
289 | ␉}␊ |
290 | ␉for (i = 0; i < lim; i++)␊ |
291 | ␉␉(void)random();␊ |
292 | }␊ |
293 | ␊ |
294 | /*␊ |
295 | * srandomdev:␊ |
296 | *␊ |
297 | * Many programs choose the seed value in a totally predictable manner.␊ |
298 | * This often causes problems. We seed the generator using the much more␊ |
299 | * secure random(4) interface. Note that this particular seeding␊ |
300 | * procedure can generate states which are impossible to reproduce by␊ |
301 | * calling srandom() with any value, since the succeeding terms in the␊ |
302 | * state buffer are no longer derived from the LC algorithm applied to␊ |
303 | * a fixed seed.␊ |
304 | */␊ |
305 | void␊ |
306 | srandomdev()␊ |
307 | {␊ |
308 | ␉int fd, done;␊ |
309 | ␉size_t len;␊ |
310 | ␊ |
311 | ␉if (rand_type == TYPE_0)␊ |
312 | ␉␉len = sizeof state[0];␊ |
313 | ␉else␊ |
314 | ␉␉len = rand_deg * sizeof state[0];␊ |
315 | ␊ |
316 | ␉done = 0;␊ |
317 | ␉fd = _open("/dev/random", O_RDONLY, 0);␊ |
318 | ␉if (fd >= 0) {␊ |
319 | ␉␉if (_read(fd, (void *) state, len) == (ssize_t) len)␊ |
320 | ␉␉␉done = 1;␊ |
321 | ␉␉_close(fd);␊ |
322 | ␉}␊ |
323 | ␊ |
324 | ␉if (!done) {␊ |
325 | ␉␉struct timeval tv;␊ |
326 | ␉␉unsigned long junk;␊ |
327 | ␊ |
328 | ␉␉gettimeofday(&tv, NULL);␊ |
329 | ␉␉srandom((getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec ^ junk);␊ |
330 | ␉␉return;␊ |
331 | ␉}␊ |
332 | ␊ |
333 | ␉if (rand_type != TYPE_0) {␊ |
334 | ␉␉fptr = &state[rand_sep];␊ |
335 | ␉␉rptr = &state[0];␊ |
336 | ␉}␊ |
337 | }␊ |
338 | ␊ |
339 | /*␊ |
340 | * initstate:␊ |
341 | *␊ |
342 | * Initialize the state information in the given array of n bytes for future␊ |
343 | * random number generation. Based on the number of bytes we are given, and␊ |
344 | * the break values for the different R.N.G.'s, we choose the best (largest)␊ |
345 | * one we can and set things up for it. srandom() is then called to␊ |
346 | * initialize the state information.␊ |
347 | *␊ |
348 | * Note that on return from srandom(), we set state[-1] to be the type␊ |
349 | * multiplexed with the current value of the rear pointer; this is so␊ |
350 | * successive calls to initstate() won't lose this information and will be␊ |
351 | * able to restart with setstate().␊ |
352 | *␊ |
353 | * Note: the first thing we do is save the current state, if any, just like␊ |
354 | * setstate() so that it doesn't matter when initstate is called.␊ |
355 | *␊ |
356 | * Returns a pointer to the old state.␊ |
357 | *␊ |
358 | * Note: The Sparc platform requires that arg_state begin on an int␊ |
359 | * word boundary; otherwise a bus error will occur. Even so, lint will␊ |
360 | * complain about mis-alignment, but you should disregard these messages.␊ |
361 | */␊ |
362 | char *␊ |
363 | initstate(seed, arg_state, n)␊ |
364 | unsigned seed;␉␉/* seed for R.N.G. */␊ |
365 | char *arg_state;␉␉/* pointer to state array */␊ |
366 | size_t n;␉␉␉␉/* # bytes of state info */␊ |
367 | {␊ |
368 | ␉char *ostate = (char *)(&state[-1]);␊ |
369 | ␉uint32_t *int_arg_state = (uint32_t *)arg_state;␊ |
370 | ␊ |
371 | ␉if (rand_type == TYPE_0)␊ |
372 | ␉␉state[-1] = rand_type;␊ |
373 | ␉else␊ |
374 | ␉␉state[-1] = MAX_TYPES * (rptr - state) + rand_type;␊ |
375 | ␉if (n < BREAK_0) {␊ |
376 | ␉␉(void)fprintf(stderr,␊ |
377 | "random: not enough state (%ld bytes); ignored.\n", n);␊ |
378 | ␉␉return(0);␊ |
379 | ␉}␊ |
380 | ␉if (n < BREAK_1) {␊ |
381 | ␉␉rand_type = TYPE_0;␊ |
382 | ␉␉rand_deg = DEG_0;␊ |
383 | ␉␉rand_sep = SEP_0;␊ |
384 | ␉} else if (n < BREAK_2) {␊ |
385 | ␉␉rand_type = TYPE_1;␊ |
386 | ␉␉rand_deg = DEG_1;␊ |
387 | ␉␉rand_sep = SEP_1;␊ |
388 | ␉} else if (n < BREAK_3) {␊ |
389 | ␉␉rand_type = TYPE_2;␊ |
390 | ␉␉rand_deg = DEG_2;␊ |
391 | ␉␉rand_sep = SEP_2;␊ |
392 | ␉} else if (n < BREAK_4) {␊ |
393 | ␉␉rand_type = TYPE_3;␊ |
394 | ␉␉rand_deg = DEG_3;␊ |
395 | ␉␉rand_sep = SEP_3;␊ |
396 | ␉} else {␊ |
397 | ␉␉rand_type = TYPE_4;␊ |
398 | ␉␉rand_deg = DEG_4;␊ |
399 | ␉␉rand_sep = SEP_4;␊ |
400 | ␉}␊ |
401 | ␉state = int_arg_state + 1; /* first location */␊ |
402 | ␉end_ptr = &state[rand_deg];␉/* must set end_ptr before srandom */␊ |
403 | ␉srandom(seed);␊ |
404 | ␉if (rand_type == TYPE_0)␊ |
405 | ␉␉int_arg_state[0] = rand_type;␊ |
406 | ␉else␊ |
407 | ␉␉int_arg_state[0] = MAX_TYPES * (rptr - state) + rand_type;␊ |
408 | ␉return(ostate);␊ |
409 | }␊ |
410 | ␊ |
411 | /*␊ |
412 | * setstate:␊ |
413 | *␊ |
414 | * Restore the state from the given state array.␊ |
415 | *␊ |
416 | * Note: it is important that we also remember the locations of the pointers␊ |
417 | * in the current state information, and restore the locations of the pointers␊ |
418 | * from the old state information. This is done by multiplexing the pointer␊ |
419 | * location into the zeroeth word of the state information.␊ |
420 | *␊ |
421 | * Note that due to the order in which things are done, it is OK to call␊ |
422 | * setstate() with the same state as the current state.␊ |
423 | *␊ |
424 | * Returns a pointer to the old state information.␊ |
425 | *␊ |
426 | * Note: The Sparc platform requires that arg_state begin on an int␊ |
427 | * word boundary; otherwise a bus error will occur. Even so, lint will␊ |
428 | * complain about mis-alignment, but you should disregard these messages.␊ |
429 | */␊ |
430 | char *␊ |
431 | setstate(arg_state)␊ |
432 | const char *arg_state;␉␉/* pointer to state array */␊ |
433 | {␊ |
434 | ␉uint32_t *new_state = (uint32_t *)arg_state;␊ |
435 | ␉uint32_t type = new_state[0] % MAX_TYPES;␊ |
436 | ␉uint32_t rear = new_state[0] / MAX_TYPES;␊ |
437 | ␉char *ostate = (char *)(&state[-1]);␊ |
438 | ␊ |
439 | ␉if (rand_type == TYPE_0)␊ |
440 | ␉␉state[-1] = rand_type;␊ |
441 | ␉else␊ |
442 | ␉␉state[-1] = MAX_TYPES * (rptr - state) + rand_type;␊ |
443 | ␉switch(type) {␊ |
444 | case TYPE_0:␊ |
445 | case TYPE_1:␊ |
446 | case TYPE_2:␊ |
447 | case TYPE_3:␊ |
448 | case TYPE_4:␊ |
449 | rand_type = type;␊ |
450 | rand_deg = degrees[type];␊ |
451 | rand_sep = seps[type];␊ |
452 | break;␊ |
453 | default:␊ |
454 | (void)fprintf(stderr,␊ |
455 | "random: state info corrupted; not changed.\n");␊ |
456 | ␉}␊ |
457 | ␉state = new_state + 1;␊ |
458 | ␉if (rand_type != TYPE_0) {␊ |
459 | ␉␉rptr = &state[rear];␊ |
460 | ␉␉fptr = &state[(rear + rand_sep) % rand_deg];␊ |
461 | ␉}␊ |
462 | ␉end_ptr = &state[rand_deg];␉␉/* set end_ptr too */␊ |
463 | ␉return(ostate);␊ |
464 | }␊ |
465 | ␊ |
466 | /*␊ |
467 | * random:␊ |
468 | *␊ |
469 | * If we are using the trivial TYPE_0 R.N.G., just do the old linear␊ |
470 | * congruential bit. Otherwise, we do our fancy trinomial stuff, which is␊ |
471 | * the same in all the other cases due to all the global variables that have␊ |
472 | * been set up. The basic operation is to add the number at the rear pointer␊ |
473 | * into the one at the front pointer. Then both pointers are advanced to␊ |
474 | * the next location cyclically in the table. The value returned is the sum␊ |
475 | * generated, reduced to 31 bits by throwing away the "least random" low bit.␊ |
476 | *␊ |
477 | * Note: the code takes advantage of the fact that both the front and␊ |
478 | * rear pointers can't wrap on the same call by not testing the rear␊ |
479 | * pointer if the front one has wrapped.␊ |
480 | *␊ |
481 | * Returns a 31-bit random number.␊ |
482 | */␊ |
483 | long␊ |
484 | random()␊ |
485 | {␊ |
486 | ␉uint32_t i;␊ |
487 | ␉uint32_t *f, *r;␊ |
488 | ␊ |
489 | ␉if (rand_type == TYPE_0) {␊ |
490 | ␉␉i = state[0];␊ |
491 | ␉␉state[0] = i = (good_rand(i)) & 0x7fffffff;␊ |
492 | ␉} else {␊ |
493 | ␉␉/*␊ |
494 | ␉␉ * Use local variables rather than static variables for speed.␊ |
495 | ␉␉ */␊ |
496 | ␉␉f = fptr; r = rptr;␊ |
497 | ␉␉*f += *r;␊ |
498 | ␉␉i = (*f >> 1) & 0x7fffffff;␉/* chucking least random bit */␊ |
499 | ␉␉if (++f >= end_ptr) {␊ |
500 | ␉␉␉f = state;␊ |
501 | ␉␉␉++r;␊ |
502 | ␉␉}␊ |
503 | ␉␉else if (++r >= end_ptr) {␊ |
504 | ␉␉␉r = state;␊ |
505 | ␉␉}␊ |
506 | ␊ |
507 | ␉␉fptr = f; rptr = r;␊ |
508 | ␉}␊ |
509 | ␉return((long)i);␊ |
510 | }␊ |
511 | |