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) 31static char sccsid[] = "@(#)random.c 8.2 (Berkeley) 5/19/95"; 32#endif /* LIBC_SCCS and not lint */ 33#include <sys/cdefs.h> 34__FBSDID("$FreeBSD$"); 35 36#ifdef __APPLE__ 37// Always compile with __DARWIN_UNIX03=1 prototypes. 38// Applications using legacy interfaces (i386 only) use types of the same size: 39// sizeof(int) == sizeof(long) == sizeof(size_t) 40#undef __DARWIN_UNIX03 41#define __DARWIN_UNIX03 1 42#endif // __APPLE__ 43 44#include "namespace.h" 45#include "namespace.h" 46#include <sys/time.h> /* for srandomdev() */ 47#include <fcntl.h> /* for srandomdev() */ 48#include <stdint.h> 49#include <stdio.h> 50#include <stdlib.h> 51#include <unistd.h> /* for srandomdev() */ 52#include "un-namespace.h" 53 54/* 55 * random.c: 56 * 57 * An improved random number generation package. In addition to the standard 58 * rand()/srand() like interface, this package also has a special state info 59 * interface. The initstate() routine is called with a seed, an array of 60 * bytes, and a count of how many bytes are being passed in; this array is 61 * then initialized to contain information for random number generation with 62 * that much state information. Good sizes for the amount of state 63 * information are 32, 64, 128, and 256 bytes. The state can be switched by 64 * calling the setstate() routine with the same array as was initiallized 65 * with initstate(). By default, the package runs with 128 bytes of state 66 * information and generates far better random numbers than a linear 67 * congruential generator. If the amount of state information is less than 68 * 32 bytes, a simple linear congruential R.N.G. is used. 69 * 70 * Internally, the state information is treated as an array of uint32_t's; the 71 * zeroeth element of the array is the type of R.N.G. being used (small 72 * integer); the remainder of the array is the state information for the 73 * R.N.G. Thus, 32 bytes of state information will give 7 ints worth of 74 * state information, which will allow a degree seven polynomial. (Note: 75 * the zeroeth word of state information also has some other information 76 * stored in it -- see setstate() for details). 77 * 78 * The random number generation technique is a linear feedback shift register 79 * approach, employing trinomials (since there are fewer terms to sum up that 80 * way). In this approach, the least significant bit of all the numbers in 81 * the state table will act as a linear feedback shift register, and will 82 * have period 2^deg - 1 (where deg is the degree of the polynomial being 83 * used, assuming that the polynomial is irreducible and primitive). The 84 * higher order bits will have longer periods, since their values are also 85 * influenced by pseudo-random carries out of the lower bits. The total 86 * period of the generator is approximately deg*(2**deg - 1); thus doubling 87 * the amount of state information has a vast influence on the period of the 88 * generator. Note: the deg*(2**deg - 1) is an approximation only good for 89 * large deg, when the period of the shift is the dominant factor. 90 * With deg equal to seven, the period is actually much longer than the 91 * 7*(2**7 - 1) predicted by this formula. 92 * 93 * Modified 28 December 1994 by Jacob S. Rosenberg. 94 * The following changes have been made: 95 * All references to the type u_int have been changed to unsigned long. 96 * All references to type int have been changed to type long. Other 97 * cleanups have been made as well. A warning for both initstate and 98 * setstate has been inserted to the effect that on Sparc platforms 99 * the 'arg_state' variable must be forced to begin on word boundaries. 100 * This can be easily done by casting a long integer array to char *. 101 * The overall logic has been left STRICTLY alone. This software was 102 * tested on both a VAX and Sun SpacsStation with exactly the same 103 * results. The new version and the original give IDENTICAL results. 104 * The new version is somewhat faster than the original. As the 105 * documentation says: "By default, the package runs with 128 bytes of 106 * state information and generates far better random numbers than a linear 107 * congruential generator. If the amount of state information is less than 108 * 32 bytes, a simple linear congruential R.N.G. is used." For a buffer of 109 * 128 bytes, this new version runs about 19 percent faster and for a 16 110 * byte buffer it is about 5 percent faster. 111 */ 112 113/* 114 * For each of the currently supported random number generators, we have a 115 * break value on the amount of state information (you need at least this 116 * many bytes of state info to support this random number generator), a degree 117 * for the polynomial (actually a trinomial) that the R.N.G. is based on, and 118 * the separation between the two lower order coefficients of the trinomial. 119 */ 120#define TYPE_0 0 /* linear congruential */ 121#define BREAK_0 8 122#define DEG_0 0 123#define SEP_0 0 124 125#define TYPE_1 1 /* x**7 + x**3 + 1 */ 126#define BREAK_1 32 127#define DEG_1 7 128#define SEP_1 3 129 130#define TYPE_2 2 /* x**15 + x + 1 */ 131#define BREAK_2 64 132#define DEG_2 15 133#define SEP_2 1 134 135#define TYPE_3 3 /* x**31 + x**3 + 1 */ 136#define BREAK_3 128 137#define DEG_3 31 138#define SEP_3 3 139 140#define TYPE_4 4 /* x**63 + x + 1 */ 141#define BREAK_4 256 142#define DEG_4 63 143#define SEP_4 1 144 145/* 146 * Array versions of the above information to make code run faster -- 147 * relies on fact that TYPE_i == i. 148 */ 149#define MAX_TYPES 5 /* max number of types above */ 150 151#ifdef USE_WEAK_SEEDING 152#define NSHUFF 0 153#else /* !USE_WEAK_SEEDING */ 154#define NSHUFF 50 /* to drop some "seed -> 1st value" linearity */ 155#endif /* !USE_WEAK_SEEDING */ 156 157static const int degrees[MAX_TYPES] = { DEG_0, DEG_1, DEG_2, DEG_3, DEG_4 }; 158static const int seps [MAX_TYPES] = { SEP_0, SEP_1, SEP_2, SEP_3, SEP_4 }; 159 160/* 161 * Initially, everything is set up as if from: 162 * 163 * initstate(1, randtbl, 128); 164 * 165 * Note that this initialization takes advantage of the fact that srandom() 166 * advances the front and rear pointers 10*rand_deg times, and hence the 167 * rear pointer which starts at 0 will also end up at zero; thus the zeroeth 168 * element of the state information, which contains info about the current 169 * position of the rear pointer is just 170 * 171 * MAX_TYPES * (rptr - state) + TYPE_3 == TYPE_3. 172 */ 173 174static uint32_t randtbl[DEG_3 + 1] = { 175 TYPE_3, 176#ifdef USE_WEAK_SEEDING 177/* Historic implementation compatibility */ 178/* The random sequences do not vary much with the seed */ 179 0x9a319039, 0x32d9c024, 0x9b663182, 0x5da1f342, 0xde3b81e0, 0xdf0a6fb5, 180 0xf103bc02, 0x48f340fb, 0x7449e56b, 0xbeb1dbb0, 0xab5c5918, 0x946554fd, 181 0x8c2e680f, 0xeb3d799f, 0xb11ee0b7, 0x2d436b86, 0xda672e2a, 0x1588ca88, 182 0xe369735d, 0x904f35f7, 0xd7158fd6, 0x6fa6f051, 0x616e6b96, 0xac94efdc, 183 0x36413f93, 0xc622c298, 0xf5a42ab8, 0x8a88d77b, 0xf5ad9d0e, 0x8999220b, 184 0x27fb47b9, 185#else /* !USE_WEAK_SEEDING */ 186 0x991539b1, 0x16a5bce3, 0x6774a4cd, 0x3e01511e, 0x4e508aaa, 0x61048c05, 187 0xf5500617, 0x846b7115, 0x6a19892c, 0x896a97af, 0xdb48f936, 0x14898454, 188 0x37ffd106, 0xb58bff9c, 0x59e17104, 0xcf918a49, 0x09378c83, 0x52c7a471, 189 0x8d293ea9, 0x1f4fc301, 0xc3db71be, 0x39b44e1c, 0xf8a44ef9, 0x4c8b80b1, 190 0x19edc328, 0x87bf4bdd, 0xc9b240e5, 0xe9ee4b1b, 0x4382aee7, 0x535b6b41, 191 0xf3bec5da 192#endif /* !USE_WEAK_SEEDING */ 193}; 194 195/* 196 * fptr and rptr are two pointers into the state info, a front and a rear 197 * pointer. These two pointers are always rand_sep places aparts, as they 198 * cycle cyclically through the state information. (Yes, this does mean we 199 * could get away with just one pointer, but the code for random() is more 200 * efficient this way). The pointers are left positioned as they would be 201 * from the call 202 * 203 * initstate(1, randtbl, 128); 204 * 205 * (The position of the rear pointer, rptr, is really 0 (as explained above 206 * in the initialization of randtbl) because the state table pointer is set 207 * to point to randtbl[1] (as explained below). 208 */ 209static uint32_t *fptr = &randtbl[SEP_3 + 1]; 210static uint32_t *rptr = &randtbl[1]; 211 212/* 213 * The following things are the pointer to the state information table, the 214 * type of the current generator, the degree of the current polynomial being 215 * used, and the separation between the two pointers. Note that for efficiency 216 * of random(), we remember the first location of the state information, not 217 * the zeroeth. Hence it is valid to access state[-1], which is used to 218 * store the type of the R.N.G. Also, we remember the last location, since 219 * this is more efficient than indexing every time to find the address of 220 * the last element to see if the front and rear pointers have wrapped. 221 */ 222static uint32_t *state = &randtbl[1]; 223static int rand_type = TYPE_3; 224static int rand_deg = DEG_3; 225static int rand_sep = SEP_3; 226static uint32_t *end_ptr = &randtbl[DEG_3 + 1]; 227 228static inline uint32_t 229good_rand(int32_t x) 230{ 231#ifdef USE_WEAK_SEEDING 232/* 233 * Historic implementation compatibility. 234 * The random sequences do not vary much with the seed, 235 * even with overflowing. 236 */ 237 return (1103515245 * x + 12345); 238#else /* !USE_WEAK_SEEDING */ 239/* 240 * Compute x = (7^5 * x) mod (2^31 - 1) 241 * wihout overflowing 31 bits: 242 * (2^31 - 1) = 127773 * (7^5) + 2836 243 * From "Random number generators: good ones are hard to find", 244 * Park and Miller, Communications of the ACM, vol. 31, no. 10, 245 * October 1988, p. 1195. 246 */ 247 int32_t hi, lo; 248 249 /* Can't be initialized with 0, so use another value. */ 250 if (x == 0) 251 x = 123459876; 252 hi = x / 127773; 253 lo = x % 127773; 254 x = 16807 * lo - 2836 * hi; 255 if (x < 0) 256 x += 0x7fffffff; 257 return (x); 258#endif /* !USE_WEAK_SEEDING */ 259} 260 261/* 262 * srandom: 263 * 264 * Initialize the random number generator based on the given seed. If the 265 * type is the trivial no-state-information type, just remember the seed. 266 * Otherwise, initializes state[] based on the given "seed" via a linear 267 * congruential generator. Then, the pointers are set to known locations 268 * that are exactly rand_sep places apart. Lastly, it cycles the state 269 * information a given number of times to get rid of any initial dependencies 270 * introduced by the L.C.R.N.G. Note that the initialization of randtbl[] 271 * for default usage relies on values produced by this routine. 272 */ 273void 274#ifdef __APPLE__ 275srandom(unsigned int x) 276#else 277srandom(unsigned long x) 278#endif 279{ 280 int i, lim; 281 282 state[0] = (uint32_t)x; 283 if (rand_type == TYPE_0) 284 lim = NSHUFF; 285 else { 286 for (i = 1; i < rand_deg; i++) 287 state[i] = good_rand(state[i - 1]); 288 fptr = &state[rand_sep]; 289 rptr = &state[0]; 290 lim = 10 * rand_deg; 291 } 292 for (i = 0; i < lim; i++) 293 (void)random(); 294} 295 296/* 297 * srandomdev: 298 * 299 * Many programs choose the seed value in a totally predictable manner. 300 * This often causes problems. We seed the generator using the much more 301 * secure random(4) interface. Note that this particular seeding 302 * procedure can generate states which are impossible to reproduce by 303 * calling srandom() with any value, since the succeeding terms in the 304 * state buffer are no longer derived from the LC algorithm applied to 305 * a fixed seed. 306 */ 307void 308srandomdev(void) 309{ 310 int fd, done; 311 size_t len; 312 313 if (rand_type == TYPE_0) 314 len = sizeof state[0]; 315 else 316 len = rand_deg * sizeof state[0]; 317 318 done = 0; 319 fd = _open("/dev/random", O_RDONLY | O_CLOEXEC, 0); 320 if (fd >= 0) { 321 if (_read(fd, (void *) state, len) == (ssize_t) len) 322 done = 1; 323 _close(fd); 324 } 325 326 if (!done) { 327 struct timeval tv; 328 329 gettimeofday(&tv, NULL); 330 srandom((getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec); 331 return; 332 } 333 334 if (rand_type != TYPE_0) { 335 fptr = &state[rand_sep]; 336 rptr = &state[0]; 337 } 338} 339 340/* 341 * initstate: 342 * 343 * Initialize the state information in the given array of n bytes for future 344 * random number generation. Based on the number of bytes we are given, and 345 * the break values for the different R.N.G.'s, we choose the best (largest) 346 * one we can and set things up for it. srandom() is then called to 347 * initialize the state information. 348 * 349 * Note that on return from srandom(), we set state[-1] to be the type 350 * multiplexed with the current value of the rear pointer; this is so 351 * successive calls to initstate() won't lose this information and will be 352 * able to restart with setstate(). 353 * 354 * Note: the first thing we do is save the current state, if any, just like 355 * setstate() so that it doesn't matter when initstate is called. 356 * 357 * Returns a pointer to the old state. 358 * 359 * Note: The Sparc platform requires that arg_state begin on an int 360 * word boundary; otherwise a bus error will occur. Even so, lint will 361 * complain about mis-alignment, but you should disregard these messages. 362 */ 363char * 364#ifdef __APPLE__ 365initstate(unsigned int seed, char *arg_state, size_t n) 366#else 367initstate(unsigned long seed, char *arg_state, long n) 368#endif 369{ 370 char *ostate = (char *)(&state[-1]); 371 uint32_t *int_arg_state = (uint32_t *)arg_state; 372 373 if (rand_type == TYPE_0) 374 state[-1] = rand_type; 375 else 376 state[-1] = MAX_TYPES * (rptr - state) + rand_type; 377 if (n < BREAK_0) { 378 (void)fprintf(stderr, 379 "random: not enough state (%ld bytes); ignored.\n", n); 380 return (0); 381 } 382 if (n < BREAK_1) { 383 rand_type = TYPE_0; 384 rand_deg = DEG_0; 385 rand_sep = SEP_0; 386 } else if (n < BREAK_2) { 387 rand_type = TYPE_1; 388 rand_deg = DEG_1; 389 rand_sep = SEP_1; 390 } else if (n < BREAK_3) { 391 rand_type = TYPE_2; 392 rand_deg = DEG_2; 393 rand_sep = SEP_2; 394 } else if (n < BREAK_4) { 395 rand_type = TYPE_3; 396 rand_deg = DEG_3; 397 rand_sep = SEP_3; 398 } else { 399 rand_type = TYPE_4; 400 rand_deg = DEG_4; 401 rand_sep = SEP_4; 402 } 403 state = int_arg_state + 1; /* first location */ 404 end_ptr = &state[rand_deg]; /* must set end_ptr before srandom */ 405 srandom(seed); 406 if (rand_type == TYPE_0) 407 int_arg_state[0] = rand_type; 408 else 409 int_arg_state[0] = MAX_TYPES * (rptr - state) + rand_type; 410 return (ostate); 411} 412 413/* 414 * setstate: 415 * 416 * Restore the state from the given state array. 417 * 418 * Note: it is important that we also remember the locations of the pointers 419 * in the current state information, and restore the locations of the pointers 420 * from the old state information. This is done by multiplexing the pointer 421 * location into the zeroeth word of the state information. 422 * 423 * Note that due to the order in which things are done, it is OK to call 424 * setstate() with the same state as the current state. 425 * 426 * Returns a pointer to the old state information. 427 * 428 * Note: The Sparc platform requires that arg_state begin on an int 429 * word boundary; otherwise a bus error will occur. Even so, lint will 430 * complain about mis-alignment, but you should disregard these messages. 431 */ 432char * 433setstate(const char *arg_state) 434{ 435 uint32_t *new_state = (uint32_t *)arg_state; 436 uint32_t type = new_state[0] % MAX_TYPES; 437 uint32_t rear = new_state[0] / MAX_TYPES; 438 char *ostate = (char *)(&state[-1]); 439 440 if (rand_type == TYPE_0) 441 state[-1] = rand_type; 442 else 443 state[-1] = MAX_TYPES * (rptr - state) + rand_type; 444 switch(type) { 445 case TYPE_0: 446 case TYPE_1: 447 case TYPE_2: 448 case TYPE_3: 449 case TYPE_4: 450 rand_type = type; 451 rand_deg = degrees[type]; 452 rand_sep = seps[type]; 453 break; 454 default: 455 (void)fprintf(stderr, 456 "random: state info corrupted; not changed.\n"); 457 } 458 state = new_state + 1; 459 if (rand_type != TYPE_0) { 460 rptr = &state[rear]; 461 fptr = &state[(rear + rand_sep) % rand_deg]; 462 } 463 end_ptr = &state[rand_deg]; /* set end_ptr too */ 464 return (ostate); 465} 466 467/* 468 * random: 469 * 470 * If we are using the trivial TYPE_0 R.N.G., just do the old linear 471 * congruential bit. Otherwise, we do our fancy trinomial stuff, which is 472 * the same in all the other cases due to all the global variables that have 473 * been set up. The basic operation is to add the number at the rear pointer 474 * into the one at the front pointer. Then both pointers are advanced to 475 * the next location cyclically in the table. The value returned is the sum 476 * generated, reduced to 31 bits by throwing away the "least random" low bit. 477 * 478 * Note: the code takes advantage of the fact that both the front and 479 * rear pointers can't wrap on the same call by not testing the rear 480 * pointer if the front one has wrapped. 481 * 482 * Returns a 31-bit random number. 483 */ 484long 485random(void) 486{ 487 uint32_t i; 488 uint32_t *f, *r; 489 490 if (rand_type == TYPE_0) { 491 i = state[0]; 492 state[0] = i = (good_rand(i)) & 0x7fffffff; 493 } else { 494 /* 495 * Use local variables rather than static variables for speed. 496 */ 497 f = fptr; r = rptr; 498 *f += *r; 499 i = (*f >> 1) & 0x7fffffff; /* chucking least random bit */ 500 if (++f >= end_ptr) { 501 f = state; 502 ++r; 503 } 504 else if (++r >= end_ptr) { 505 r = state; 506 } 507 508 fptr = f; rptr = r; 509 } 510 return ((long)i); 511} 512