/* * CDDL HEADER START * * The contents of this file are subject to the terms of the * Common Development and Distribution License (the "License"). * You may not use this file except in compliance with the License. * * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE * or http://www.opensolaris.org/os/licensing. * See the License for the specific language governing permissions * and limitations under the License. * * When distributing Covered Code, include this CDDL HEADER in each * file and include the License file at usr/src/OPENSOLARIS.LICENSE. * If applicable, add the following below this CDDL HEADER, with the * fields enclosed by brackets "[]" replaced with your own identifying * information: Portions Copyright [yyyy] [name of copyright owner] * * CDDL HEADER END */ /* * Copyright 2008 Sun Microsystems, Inc. All rights reserved. * Use is subject to license terms. */ /* Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */ /* All Rights Reserved */ /* * University Copyright- Copyright (c) 1982, 1986, 1988 * The Regents of the University of California * All Rights Reserved * * University Acknowledgment- Portions of this document are derived from * software developed by the University of California, Berkeley, and its * contributors. */ #include "lint.h" #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <limits.h> /* * random.c: * An improved random number generation package. In addition to the standard * rand()/srand() like interface, this package also has a special state info * interface. The initstate() routine is called with a seed, an array of * bytes, and a count of how many bytes are being passed in; this array is then * initialized to contain information for random number generation with that * much state information. Good sizes for the amount of state information are * 32, 64, 128, and 256 bytes. The state can be switched by calling the * setstate() routine with the same array as was initiallized with initstate(). * By default, the package runs with 128 bytes of state information and * generates far better random numbers than a linear congruential generator. * If the amount of state information is less than 32 bytes, a simple linear * congruential R.N.G. is used. * Internally, the state information is treated as an array of ints; the * zeroeth element of the array is the type of R.N.G. being used (small * integer); the remainder of the array is the state information for the * R.N.G. Thus, 32 bytes of state information will give 7 ints worth of * state information, which will allow a degree seven polynomial. (Note: the * zeroeth word of state information also has some other information stored * in it -- see setstate() for details). * The random number generation technique is a linear feedback shift register * approach, employing trinomials (since there are fewer terms to sum up that * way). In this approach, the least significant bit of all the numbers in * the state table will act as a linear feedback shift register, and will have * period 2^deg - 1 (where deg is the degree of the polynomial being used, * assuming that the polynomial is irreducible and primitive). The higher * order bits will have longer periods, since their values are also influenced * by pseudo-random carries out of the lower bits. The total period of the * generator is approximately deg*(2**deg - 1); thus doubling the amount of * state information has a vast influence on the period of the generator. * Note: the deg*(2**deg - 1) is an approximation only good for large deg, * when the period of the shift register is the dominant factor. With deg * equal to seven, the period is actually much longer than the 7*(2**7 - 1) * predicted by this formula. */ /* * For each of the currently supported random number generators, we have a * break value on the amount of state information (you need at least this * many bytes of state info to support this random number generator), a degree * for the polynomial (actually a trinomial) that the R.N.G. is based on, and * the separation between the two lower order coefficients of the trinomial. */ #define TYPE_0 0 /* linear congruential */ #define BREAK_0 8 #define DEG_0 0 #define SEP_0 0 #define TYPE_1 1 /* x**7 + x**3 + 1 */ #define BREAK_1 32 #define DEG_1 7 #define SEP_1 3 #define TYPE_2 2 /* x**15 + x + 1 */ #define BREAK_2 64 #define DEG_2 15 #define SEP_2 1 #define TYPE_3 3 /* x**31 + x**3 + 1 */ #define BREAK_3 128 #define DEG_3 31 #define SEP_3 3 #define TYPE_4 4 /* x**63 + x + 1 */ #define BREAK_4 256 #define DEG_4 63 #define SEP_4 1 /* * Array versions of the above information to make code run faster -- relies * on fact that TYPE_i == i. */ #define MAX_TYPES 5 /* max number of types above */ static struct _randomjunk { unsigned int degrees[MAX_TYPES]; unsigned int seps[MAX_TYPES]; unsigned int randtbl[ DEG_3 + 1 ]; /* * fptr and rptr are two pointers into the state info, a front and a rear * pointer. These two pointers are always rand_sep places aparts, as they cycle * cyclically through the state information. (Yes, this does mean we could get * away with just one pointer, but the code for random() is more efficient this * way). The pointers are left positioned as they would be from the call * initstate( 1, randtbl, 128 ) * (The position of the rear pointer, rptr, is really 0 (as explained above * in the initialization of randtbl) because the state table pointer is set * to point to randtbl[1] (as explained below). */ unsigned int *fptr, *rptr; /* * The following things are the pointer to the state information table, * the type of the current generator, the degree of the current polynomial * being used, and the separation between the two pointers. * Note that for efficiency of random(), we remember the first location of * the state information, not the zeroeth. Hence it is valid to access * state[-1], which is used to store the type of the R.N.G. * Also, we remember the last location, since this is more efficient than * indexing every time to find the address of the last element to see if * the front and rear pointers have wrapped. */ unsigned int *state; unsigned int rand_type, rand_deg, rand_sep; unsigned int *end_ptr; } *__randomjunk, *_randomjunk(void), _randominit = { /* * Initially, everything is set up as if from : * initstate( 1, &randtbl, 128 ); * Note that this initialization takes advantage of the fact * that srandom() advances the front and rear pointers 10*rand_deg * times, and hence the rear pointer which starts at 0 will also * end up at zero; thus the zeroeth element of the state * information, which contains info about the current * position of the rear pointer is just * MAX_TYPES*(rptr - state) + TYPE_3 == TYPE_3. */ { DEG_0, DEG_1, DEG_2, DEG_3, DEG_4 }, { SEP_0, SEP_1, SEP_2, SEP_3, SEP_4 }, { TYPE_3, 0x9a319039U, 0x32d9c024U, 0x9b663182U, 0x5da1f342U, 0xde3b81e0U, 0xdf0a6fb5U, 0xf103bc02U, 0x48f340fbU, 0x7449e56bU, 0xbeb1dbb0U, 0xab5c5918U, 0x946554fdU, 0x8c2e680fU, 0xeb3d799fU, 0xb11ee0b7U, 0x2d436b86U, 0xda672e2aU, 0x1588ca88U, 0xe369735dU, 0x904f35f7U, 0xd7158fd6U, 0x6fa6f051U, 0x616e6b96U, 0xac94efdcU, 0x36413f93U, 0xc622c298U, 0xf5a42ab8U, 0x8a88d77bU, 0xf5ad9d0eU, 0x8999220bU, 0x27fb47b9U }, &_randominit.randtbl[ SEP_3 + 1 ], &_randominit.randtbl[ 1 ], &_randominit.randtbl[ 1 ], TYPE_3, DEG_3, SEP_3, &_randominit.randtbl[ DEG_3 + 1] }; static struct _randomjunk * _randomjunk(void) { struct _randomjunk *rp = __randomjunk; if (rp == NULL) { rp = (struct _randomjunk *)malloc(sizeof (*rp)); if (rp == NULL) return (NULL); (void) memcpy(rp, &_randominit, sizeof (*rp)); __randomjunk = rp; } return (rp); } /* * initstate: * Initialize the state information in the given array of n bytes for * future random number generation. Based on the number of bytes we * are given, and the break values for the different R.N.G.'s, we choose * the best (largest) one we can and set things up for it. srandom() is * then called to initialize the state information. * Note that on return from srandom(), we set state[-1] to be the type * multiplexed with the current value of the rear pointer; this is so * successive calls to initstate() won't lose this information and will * be able to restart with setstate(). * Note: the first thing we do is save the current state, if any, just like * setstate() so that it doesn't matter when initstate is called. * Returns a pointer to the old state. */ char * initstate( unsigned int seed, /* seed for R. N. G. */ char *arg_state, /* pointer to state array */ size_t size) /* # bytes of state info */ { unsigned int n; struct _randomjunk *rp = _randomjunk(); char *ostate; if (size > UINT_MAX) n = UINT_MAX; else n = (unsigned int)size; if (rp == NULL) return (NULL); ostate = (char *)(&rp->state[ -1 ]); if (rp->rand_type == TYPE_0) rp->state[ -1 ] = rp->rand_type; else rp->state[ -1 ] = (unsigned int)(MAX_TYPES*(rp->rptr - rp->state) + rp->rand_type); if (n < BREAK_1) { if (n < BREAK_0) { return (NULL); } rp->rand_type = TYPE_0; rp->rand_deg = DEG_0; rp->rand_sep = SEP_0; } else { if (n < BREAK_2) { rp->rand_type = TYPE_1; rp->rand_deg = DEG_1; rp->rand_sep = SEP_1; } else { if (n < BREAK_3) { rp->rand_type = TYPE_2; rp->rand_deg = DEG_2; rp->rand_sep = SEP_2; } else { if (n < BREAK_4) { rp->rand_type = TYPE_3; rp->rand_deg = DEG_3; rp->rand_sep = SEP_3; } else { rp->rand_type = TYPE_4; rp->rand_deg = DEG_4; rp->rand_sep = SEP_4; } } } } /* first location */ rp->state = &(((unsigned int *)(uintptr_t)arg_state)[1]); /* must set end_ptr before srandom */ rp->end_ptr = &rp->state[rp->rand_deg]; srandom(seed); if (rp->rand_type == TYPE_0) rp->state[ -1 ] = rp->rand_type; else rp->state[-1] = (unsigned int)(MAX_TYPES* (rp->rptr - rp->state) + rp->rand_type); return (ostate); } /* * setstate: * Restore the state from the given state array. * Note: it is important that we also remember the locations of the pointers * in the current state information, and restore the locations of the pointers * from the old state information. This is done by multiplexing the pointer * location into the zeroeth word of the state information. * Note that due to the order in which things are done, it is OK to call * setstate() with the same state as the current state. * Returns a pointer to the old state information. */ char * setstate(const char *arg_state) { struct _randomjunk *rp = _randomjunk(); unsigned int *new_state; unsigned int type; unsigned int rear; char *ostate; if (rp == NULL) return (NULL); new_state = (unsigned int *)(uintptr_t)arg_state; type = new_state[0]%MAX_TYPES; rear = new_state[0]/MAX_TYPES; ostate = (char *)(&rp->state[ -1 ]); if (rp->rand_type == TYPE_0) rp->state[ -1 ] = rp->rand_type; else rp->state[-1] = (unsigned int)(MAX_TYPES* (rp->rptr - rp->state) + rp->rand_type); switch (type) { case TYPE_0: case TYPE_1: case TYPE_2: case TYPE_3: case TYPE_4: rp->rand_type = type; rp->rand_deg = rp->degrees[ type ]; rp->rand_sep = rp->seps[ type ]; break; default: return (NULL); } rp->state = &new_state[ 1 ]; if (rp->rand_type != TYPE_0) { rp->rptr = &rp->state[ rear ]; rp->fptr = &rp->state[ (rear + rp->rand_sep)%rp->rand_deg ]; } rp->end_ptr = &rp->state[ rp->rand_deg ]; /* set end_ptr too */ return (ostate); } /* * random: * If we are using the trivial TYPE_0 R.N.G., just do the old linear * congruential bit. Otherwise, we do our fancy trinomial stuff, which is the * same in all ther other cases due to all the global variables that have been * set up. The basic operation is to add the number at the rear pointer into * the one at the front pointer. Then both pointers are advanced to the next * location cyclically in the table. The value returned is the sum generated, * reduced to 31 bits by throwing away the "least random" low bit. * Note: the code takes advantage of the fact that both the front and * rear pointers can't wrap on the same call by not testing the rear * pointer if the front one has wrapped. * Returns a 31-bit random number. */ long random(void) { struct _randomjunk *rp = _randomjunk(); unsigned int i; if (rp == NULL) return (0L); if (rp->rand_type == TYPE_0) { i = rp->state[0] = (rp->state[0]*1103515245 + 12345)&0x7fffffff; } else { *rp->fptr += *rp->rptr; i = (*rp->fptr >> 1)&0x7fffffff; /* chucking least random bit */ if (++rp->fptr >= rp->end_ptr) { rp->fptr = rp->state; ++rp->rptr; } else { if (++rp->rptr >= rp->end_ptr) rp->rptr = rp->state; } } return ((long)i); } /* * srandom: * Initialize the random number generator based on the given seed. If the * type is the trivial no-state-information type, just remember the seed. * Otherwise, initializes state[] based on the given "seed" via a linear * congruential generator. Then, the pointers are set to known locations * that are exactly rand_sep places apart. Lastly, it cycles the state * information a given number of times to get rid of any initial dependencies * introduced by the L.C.R.N.G. * Note that the initialization of randtbl[] for default usage relies on * values produced by this routine. */ void srandom(unsigned int x) { struct _randomjunk *rp = _randomjunk(); unsigned int i; if (rp == NULL) return; if (rp->rand_type == TYPE_0) { rp->state[ 0 ] = x; } else { rp->state[ 0 ] = x; for (i = 1; i < rp->rand_deg; i++) { rp->state[i] = 1103515245*rp->state[i - 1] + 12345; } rp->fptr = &rp->state[ rp->rand_sep ]; rp->rptr = &rp->state[ 0 ]; for (i = 0; i < 10*rp->rand_deg; i++) (void)random(); } }
