+++ /dev/null
-/*
- * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
- *
- * @APPLE_LICENSE_HEADER_START@
- *
- * Copyright (c) 1999-2003 Apple Computer, Inc. All Rights Reserved.
- *
- * This file contains Original Code and/or Modifications of Original Code
- * as defined in and that are subject to the Apple Public Source License
- * Version 2.0 (the 'License'). You may not use this file except in
- * compliance with the License. Please obtain a copy of the License at
- * http://www.opensource.apple.com/apsl/ and read it before using this
- * file.
- *
- * The Original Code and all software distributed under the License are
- * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
- * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
- * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
- * Please see the License for the specific language governing rights and
- * limitations under the License.
- *
- * @APPLE_LICENSE_HEADER_END@
- */
-/*
- * 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. All advertising materials mentioning features or use of this software
- * must display the following acknowledgement:
- * This product includes software developed by the University of
- * California, Berkeley and its contributors.
- * 4. 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.
- */
-
-
-#include <stdio.h>
-#include <stdlib.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 longs; 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 longs 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 long degrees[MAX_TYPES] = { DEG_0, DEG_1, DEG_2, DEG_3, DEG_4 };
-static long 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.
- */
-
-static long randtbl[DEG_3 + 1] = {
- TYPE_3,
- 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,
-};
-
-/*
- * 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 long *fptr = &randtbl[SEP_3 + 1];
-static long *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 long *state = &randtbl[1];
-static long rand_type = TYPE_3;
-static long rand_deg = DEG_3;
-static long rand_sep = SEP_3;
-static long *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.
- */
-void
-srandom(x)
- unsigned long x;
-{
- register long i;
-
- if (rand_type == TYPE_0)
- state[0] = x;
- else {
- state[0] = x;
- for (i = 1; i < rand_deg; i++)
- state[i] = 1103515245 * state[i - 1] + 12345;
- fptr = &state[rand_sep];
- rptr = &state[0];
- for (i = 0; i < 10 * rand_deg; i++)
- (void)random();
- }
-}
-
-/*
- * 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 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 *
-initstate(seed, arg_state, n)
- unsigned long seed; /* seed for R.N.G. */
- char *arg_state; /* pointer to state array */
- long n; /* # bytes of state info */
-{
- register char *ostate = (char *)(&state[-1]);
- register long *long_arg_state = (long *) arg_state;
-
- if (rand_type == TYPE_0)
- state[-1] = rand_type;
- else
- state[-1] = MAX_TYPES * (rptr - state) + rand_type;
- if (n < BREAK_0) {
- (void)fprintf(stderr,
- "random: not enough state (%ld bytes); ignored.\n", n);
- return(0);
- }
- 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 = (long *) (long_arg_state + 1); /* first location */
- end_ptr = &state[rand_deg]; /* must set end_ptr before srandom */
- srandom(seed);
- if (rand_type == TYPE_0)
- long_arg_state[0] = rand_type;
- else
- long_arg_state[0] = MAX_TYPES * (rptr - state) + 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.
- *
- * 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(arg_state)
- char *arg_state; /* pointer to state array */
-{
- register long *new_state = (long *) arg_state;
- register long type = new_state[0] % MAX_TYPES;
- register long rear = new_state[0] / MAX_TYPES;
- char *ostate = (char *)(&state[-1]);
-
- if (rand_type == TYPE_0)
- state[-1] = rand_type;
- else
- state[-1] = MAX_TYPES * (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:
- (void)fprintf(stderr,
- "random: state info corrupted; not changed.\n");
- }
- state = (long *) (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 */
- 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 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.
- */
-long
-random()
-{
- register long i;
- register long *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;
- i = (*f >> 1) & 0x7fffffff; /* chucking least random bit */
- if (++f >= end_ptr) {
- f = state;
- ++r;
- }
- else if (++r >= end_ptr) {
- r = state;
- }
-
- fptr = f; rptr = r;
- }
- return(i);
-}
projects / apple / libc.git / blobdiff