| 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 | |
