| /* $NetBSD: random.c,v 1.5 2016/02/08 05:27:24 dholland Exp $ */ |
| |
| /* |
| * Copyright (c) 1983, 1993 |
| * The Regents of the University of California. All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 3. Neither the name of the University nor the names of its contributors |
| * may be used to endorse or promote products derived from this software |
| * without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
| * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| */ |
| |
| #if !defined(_KERNEL) && !defined(_STANDALONE) |
| #include <sys/cdefs.h> |
| #if defined(LIBC_SCCS) && !defined(lint) |
| #if 0 |
| static char sccsid[] = "@(#)random.c 8.2 (Berkeley) 5/19/95"; |
| #else |
| __RCSID("$NetBSD: random.c,v 1.5 2016/02/08 05:27:24 dholland Exp $"); |
| #endif |
| #endif /* LIBC_SCCS and not lint */ |
| |
| #include "namespace.h" |
| |
| #include <assert.h> |
| #include <errno.h> |
| #include <stdlib.h> |
| #include "reentrant.h" |
| |
| #ifdef __weak_alias |
| __weak_alias(initstate,_initstate) |
| __weak_alias(random,_random) |
| __weak_alias(setstate,_setstate) |
| __weak_alias(srandom,_srandom) |
| #endif |
| |
| |
| #ifdef _REENTRANT |
| static mutex_t random_mutex = MUTEX_INITIALIZER; |
| #endif |
| #else |
| #include <lib/libkern/libkern.h> |
| #define mutex_lock(a) (void)0 |
| #define mutex_unlock(a) (void)0 |
| #endif |
| |
| #ifndef SMALL_RANDOM |
| static void srandom_unlocked(unsigned int); |
| static long random_unlocked(void); |
| |
| #define USE_BETTER_RANDOM |
| |
| /* |
| * 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. |
| * |
| * Modified 28 December 1994 by Jacob S. Rosenberg. |
| * The following changes have been made: |
| * All references to the type u_int have been changed to unsigned long. |
| * All references to type int have been changed to type long. Other |
| * cleanups have been made as well. A warning for both initstate and |
| * setstate has been inserted to the effect that on Sparc platforms |
| * the 'arg_state' variable must be forced to begin on word boundaries. |
| * This can be easily done by casting a long integer array to char *. |
| * The overall logic has been left STRICTLY alone. This software was |
| * tested on both a VAX and Sun SpacsStation with exactly the same |
| * results. The new version and the original give IDENTICAL results. |
| * The new version is somewhat faster than the original. As the |
| * documentation says: "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." For a buffer of |
| * 128 bytes, this new version runs about 19 percent faster and for a 16 |
| * byte buffer it is about 5 percent faster. |
| * |
| * Modified 07 January 2002 by Jason R. Thorpe. |
| * The following changes have been made: |
| * All the references to "long" have been changed back to "int". This |
| * fixes memory corruption problems on LP64 platforms. |
| */ |
| |
| /* |
| * 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 const int degrees[MAX_TYPES] = { DEG_0, DEG_1, DEG_2, DEG_3, DEG_4 }; |
| static const int seps[MAX_TYPES] = { SEP_0, SEP_1, SEP_2, SEP_3, SEP_4 }; |
| |
| /* |
| * 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. |
| */ |
| |
| /* LINTED */ |
| static int randtbl[DEG_3 + 1] = { |
| TYPE_3, |
| #ifdef USE_BETTER_RANDOM |
| 0x991539b1, 0x16a5bce3, 0x6774a4cd, |
| 0x3e01511e, 0x4e508aaa, 0x61048c05, |
| 0xf5500617, 0x846b7115, 0x6a19892c, |
| 0x896a97af, 0xdb48f936, 0x14898454, |
| 0x37ffd106, 0xb58bff9c, 0x59e17104, |
| 0xcf918a49, 0x09378c83, 0x52c7a471, |
| 0x8d293ea9, 0x1f4fc301, 0xc3db71be, |
| 0x39b44e1c, 0xf8a44ef9, 0x4c8b80b1, |
| 0x19edc328, 0x87bf4bdd, 0xc9b240e5, |
| 0xe9ee4b1b, 0x4382aee7, 0x535b6b41, |
| 0xf3bec5da, |
| #else |
| 0x9a319039, 0x32d9c024, 0x9b663182, |
| 0x5da1f342, 0xde3b81e0, 0xdf0a6fb5, |
| 0xf103bc02, 0x48f340fb, 0x7449e56b, |
| 0xbeb1dbb0, 0xab5c5918, 0x946554fd, |
| 0x8c2e680f, 0xeb3d799f, 0xb11ee0b7, |
| 0x2d436b86, 0xda672e2a, 0x1588ca88, |
| 0xe369735d, 0x904f35f7, 0xd7158fd6, |
| 0x6fa6f051, 0x616e6b96, 0xac94efdc, |
| 0x36413f93, 0xc622c298, 0xf5a42ab8, |
| 0x8a88d77b, 0xf5ad9d0e, 0x8999220b, |
| 0x27fb47b9, |
| #endif /* USE_BETTER_RANDOM */ |
| }; |
| |
| /* |
| * 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). |
| */ |
| static int *fptr = &randtbl[SEP_3 + 1]; |
| static int *rptr = &randtbl[1]; |
| |
| /* |
| * 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. |
| */ |
| static int *state = &randtbl[1]; |
| static int rand_type = TYPE_3; |
| static int rand_deg = DEG_3; |
| static int rand_sep = SEP_3; |
| static int *end_ptr = &randtbl[DEG_3 + 1]; |
| |
| /* |
| * 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. |
| */ |
| static void |
| srandom_unlocked(unsigned int x) |
| { |
| int i; |
| |
| if (rand_type == TYPE_0) |
| state[0] = x; |
| else { |
| state[0] = x; |
| for (i = 1; i < rand_deg; i++) { |
| #ifdef USE_BETTER_RANDOM |
| int x1, hi, lo, t; |
| |
| /* |
| * Compute x[n + 1] = (7^5 * x[n]) mod (2^31 - 1). |
| * From "Random number generators: good ones are hard |
| * to find", Park and Miller, Communications of the ACM, |
| * vol. 31, no. 10, |
| * October 1988, p. 1195. |
| */ |
| x1 = state[i - 1]; |
| hi = x1 / 127773; |
| lo = x1 % 127773; |
| t = 16807 * lo - 2836 * hi; |
| if (t <= 0) |
| t += 0x7fffffff; |
| state[i] = t; |
| #else |
| state[i] = 1103515245 * state[i - 1] + 12345; |
| #endif /* USE_BETTER_RANDOM */ |
| } |
| fptr = &state[rand_sep]; |
| rptr = &state[0]; |
| for (i = 0; i < 10 * rand_deg; i++) |
| (void)random_unlocked(); |
| } |
| } |
| |
| void |
| srandom(unsigned int x) |
| { |
| |
| mutex_lock(&random_mutex); |
| srandom_unlocked(x); |
| mutex_unlock(&random_mutex); |
| } |
| |
| /* |
| * 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. |
| * |
| * Note: The Sparc platform requires that arg_state begin on an int |
| * word boundary; otherwise a bus error will occur. Even so, lint will |
| * complain about mis-alignment, but you should disregard these messages. |
| */ |
| char * |
| initstate( |
| unsigned int seed, /* seed for R.N.G. */ |
| char *arg_state, /* pointer to state array */ |
| size_t n) /* # bytes of state info */ |
| { |
| void *ostate = (void *)(&state[-1]); |
| int *int_arg_state; |
| |
| _DIAGASSERT(arg_state != NULL); |
| |
| int_arg_state = (int *)(void *)arg_state; |
| |
| mutex_lock(&random_mutex); |
| if (rand_type == TYPE_0) |
| state[-1] = rand_type; |
| else |
| state[-1] = MAX_TYPES * (int)(rptr - state) + rand_type; |
| if (n < BREAK_0) { |
| mutex_unlock(&random_mutex); |
| return (NULL); |
| } else if (n < BREAK_1) { |
| rand_type = TYPE_0; |
| rand_deg = DEG_0; |
| rand_sep = SEP_0; |
| } else if (n < BREAK_2) { |
| rand_type = TYPE_1; |
| rand_deg = DEG_1; |
| rand_sep = SEP_1; |
| } else if (n < BREAK_3) { |
| rand_type = TYPE_2; |
| rand_deg = DEG_2; |
| rand_sep = SEP_2; |
| } else if (n < BREAK_4) { |
| rand_type = TYPE_3; |
| rand_deg = DEG_3; |
| rand_sep = SEP_3; |
| } else { |
| rand_type = TYPE_4; |
| rand_deg = DEG_4; |
| rand_sep = SEP_4; |
| } |
| state = (int *) (int_arg_state + 1); /* first location */ |
| end_ptr = &state[rand_deg]; /* must set end_ptr before srandom */ |
| srandom_unlocked(seed); |
| if (rand_type == TYPE_0) |
| int_arg_state[0] = rand_type; |
| else |
| int_arg_state[0] = MAX_TYPES * (int)(rptr - state) + rand_type; |
| mutex_unlock(&random_mutex); |
| return((char *)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. |
| * |
| * Note: The Sparc platform requires that arg_state begin on a long |
| * word boundary; otherwise a bus error will occur. Even so, lint will |
| * complain about mis-alignment, but you should disregard these messages. |
| */ |
| char * |
| setstate(char *arg_state) /* pointer to state array */ |
| { |
| int *new_state; |
| int type; |
| int rear; |
| void *ostate = (void *)(&state[-1]); |
| |
| _DIAGASSERT(arg_state != NULL); |
| |
| new_state = (int *)(void *)arg_state; |
| type = (int)(new_state[0] % MAX_TYPES); |
| rear = (int)(new_state[0] / MAX_TYPES); |
| |
| mutex_lock(&random_mutex); |
| if (rand_type == TYPE_0) |
| state[-1] = rand_type; |
| else |
| state[-1] = MAX_TYPES * (int)(rptr - state) + rand_type; |
| switch(type) { |
| case TYPE_0: |
| case TYPE_1: |
| case TYPE_2: |
| case TYPE_3: |
| case TYPE_4: |
| rand_type = type; |
| rand_deg = degrees[type]; |
| rand_sep = seps[type]; |
| break; |
| default: |
| mutex_unlock(&random_mutex); |
| return (NULL); |
| } |
| state = (int *) (new_state + 1); |
| if (rand_type != TYPE_0) { |
| rptr = &state[rear]; |
| fptr = &state[(rear + rand_sep) % rand_deg]; |
| } |
| end_ptr = &state[rand_deg]; /* set end_ptr too */ |
| mutex_unlock(&random_mutex); |
| return((char *)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 the 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. |
| */ |
| static long |
| random_unlocked(void) |
| { |
| int i; |
| int *f, *r; |
| |
| if (rand_type == TYPE_0) { |
| i = state[0]; |
| state[0] = i = (i * 1103515245 + 12345) & 0x7fffffff; |
| } else { |
| /* |
| * Use local variables rather than static variables for speed. |
| */ |
| f = fptr; r = rptr; |
| *f += *r; |
| /* chucking least random bit */ |
| i = ((unsigned int)*f >> 1) & 0x7fffffff; |
| if (++f >= end_ptr) { |
| f = state; |
| ++r; |
| } |
| else if (++r >= end_ptr) { |
| r = state; |
| } |
| |
| fptr = f; rptr = r; |
| } |
| return(i); |
| } |
| |
| long |
| random(void) |
| { |
| long r; |
| |
| mutex_lock(&random_mutex); |
| r = random_unlocked(); |
| mutex_unlock(&random_mutex); |
| return (r); |
| } |
| #else |
| long |
| random(void) |
| { |
| static u_long randseed = 1; |
| long x, hi, lo, t; |
| |
| /* |
| * Compute x[n + 1] = (7^5 * x[n]) mod (2^31 - 1). |
| * From "Random number generators: good ones are hard to find", |
| * Park and Miller, Communications of the ACM, vol. 31, no. 10, |
| * October 1988, p. 1195. |
| */ |
| x = randseed; |
| hi = x / 127773; |
| lo = x % 127773; |
| t = 16807 * lo - 2836 * hi; |
| if (t <= 0) |
| t += 0x7fffffff; |
| randseed = t; |
| return (t); |
| } |
| #endif /* SMALL_RANDOM */ |