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/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License, Version 1.0 only
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* (the "License"). You may not use this file except in compliance
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* with the License.
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*
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* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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* or http://www.opensolaris.org/os/licensing.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information: Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*/
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/*
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* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
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* Use is subject to license terms.
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*/
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/* Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
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/* All Rights Reserved */
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/*
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* University Copyright- Copyright (c) 1982, 1986, 1988
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* The Regents of the University of California
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* All Rights Reserved
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*
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* University Acknowledgment- Portions of this document are derived from
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* software developed by the University of California, Berkeley, and its
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* contributors.
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*/
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#pragma ident "%Z%%M% %I% %E% SMI"
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#include "synonyms.h"
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/types.h>
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#include <limits.h>
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/*
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* random.c:
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* An improved random number generation package. In addition to the standard
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* rand()/srand() like interface, this package also has a special state info
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* interface. The initstate() routine is called with a seed, an array of
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* bytes, and a count of how many bytes are being passed in; this array is then
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* initialized to contain information for random number generation with that
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* much state information. Good sizes for the amount of state information are
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* 32, 64, 128, and 256 bytes. The state can be switched by calling the
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* setstate() routine with the same array as was initiallized with initstate().
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* By default, the package runs with 128 bytes of state information and
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* generates far better random numbers than a linear congruential generator.
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* If the amount of state information is less than 32 bytes, a simple linear
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* congruential R.N.G. is used.
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* Internally, the state information is treated as an array of ints; the
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* zeroeth element of the array is the type of R.N.G. being used (small
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* integer); the remainder of the array is the state information for the
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* R.N.G. Thus, 32 bytes of state information will give 7 ints worth of
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* state information, which will allow a degree seven polynomial. (Note: the
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* zeroeth word of state information also has some other information stored
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* in it -- see setstate() for details).
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* The random number generation technique is a linear feedback shift register
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* approach, employing trinomials (since there are fewer terms to sum up that
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* way). In this approach, the least significant bit of all the numbers in
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* the state table will act as a linear feedback shift register, and will have
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* period 2^deg - 1 (where deg is the degree of the polynomial being used,
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* assuming that the polynomial is irreducible and primitive). The higher
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* order bits will have longer periods, since their values are also influenced
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* by pseudo-random carries out of the lower bits. The total period of the
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* generator is approximately deg*(2**deg - 1); thus doubling the amount of
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* state information has a vast influence on the period of the generator.
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* Note: the deg*(2**deg - 1) is an approximation only good for large deg,
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* when the period of the shift register is the dominant factor. With deg
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* equal to seven, the period is actually much longer than the 7*(2**7 - 1)
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* predicted by this formula.
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*/
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/*
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* For each of the currently supported random number generators, we have a
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* break value on the amount of state information (you need at least this
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* many bytes of state info to support this random number generator), a degree
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* for the polynomial (actually a trinomial) that the R.N.G. is based on, and
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* the separation between the two lower order coefficients of the trinomial.
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*/
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#define TYPE_0 0 /* linear congruential */
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#define BREAK_0 8
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#define DEG_0 0
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#define SEP_0 0
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#define TYPE_1 1 /* x**7 + x**3 + 1 */
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#define BREAK_1 32
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#define DEG_1 7
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#define SEP_1 3
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#define TYPE_2 2 /* x**15 + x + 1 */
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#define BREAK_2 64
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#define DEG_2 15
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#define SEP_2 1
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#define TYPE_3 3 /* x**31 + x**3 + 1 */
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#define BREAK_3 128
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#define DEG_3 31
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#define SEP_3 3
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#define TYPE_4 4 /* x**63 + x + 1 */
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#define BREAK_4 256
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#define DEG_4 63
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#define SEP_4 1
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/*
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* Array versions of the above information to make code run faster -- relies
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* on fact that TYPE_i == i.
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*/
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#define MAX_TYPES 5 /* max number of types above */
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static struct _randomjunk {
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unsigned int degrees[MAX_TYPES];
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unsigned int seps[MAX_TYPES];
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unsigned int randtbl[ DEG_3 + 1 ];
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/*
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* fptr and rptr are two pointers into the state info, a front and a rear
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* pointer. These two pointers are always rand_sep places aparts, as they cycle
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* cyclically through the state information. (Yes, this does mean we could get
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* away with just one pointer, but the code for random() is more efficient this
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* way). The pointers are left positioned as they would be from the call
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* initstate( 1, randtbl, 128 )
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* (The position of the rear pointer, rptr, is really 0 (as explained above
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* in the initialization of randtbl) because the state table pointer is set
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* to point to randtbl[1] (as explained below).
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*/
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unsigned int *fptr, *rptr;
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/*
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* The following things are the pointer to the state information table,
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* the type of the current generator, the degree of the current polynomial
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* being used, and the separation between the two pointers.
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* Note that for efficiency of random(), we remember the first location of
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* the state information, not the zeroeth. Hence it is valid to access
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* state[-1], which is used to store the type of the R.N.G.
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* Also, we remember the last location, since this is more efficient than
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* indexing every time to find the address of the last element to see if
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* the front and rear pointers have wrapped.
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*/
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unsigned int *state;
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unsigned int rand_type, rand_deg, rand_sep;
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unsigned int *end_ptr;
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} *__randomjunk, *_randomjunk(void), _randominit = {
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/*
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* Initially, everything is set up as if from :
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* initstate( 1, &randtbl, 128 );
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* Note that this initialization takes advantage of the fact
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* that srandom() advances the front and rear pointers 10*rand_deg
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* times, and hence the rear pointer which starts at 0 will also
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* end up at zero; thus the zeroeth element of the state
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* information, which contains info about the current
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* position of the rear pointer is just
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* MAX_TYPES*(rptr - state) + TYPE_3 == TYPE_3.
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*/
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{ DEG_0, DEG_1, DEG_2, DEG_3, DEG_4 },
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{ SEP_0, SEP_1, SEP_2, SEP_3, SEP_4 },
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{ TYPE_3,
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0x9a319039U, 0x32d9c024U, 0x9b663182U, 0x5da1f342U,
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0xde3b81e0U, 0xdf0a6fb5U, 0xf103bc02U, 0x48f340fbU,
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0x7449e56bU, 0xbeb1dbb0U, 0xab5c5918U, 0x946554fdU,
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0x8c2e680fU, 0xeb3d799fU, 0xb11ee0b7U, 0x2d436b86U,
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0xda672e2aU, 0x1588ca88U, 0xe369735dU, 0x904f35f7U,
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0xd7158fd6U, 0x6fa6f051U, 0x616e6b96U, 0xac94efdcU,
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0x36413f93U, 0xc622c298U, 0xf5a42ab8U, 0x8a88d77bU,
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0xf5ad9d0eU, 0x8999220bU, 0x27fb47b9U },
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&_randominit.randtbl[ SEP_3 + 1 ],
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&_randominit.randtbl[ 1 ],
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&_randominit.randtbl[ 1 ],
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TYPE_3, DEG_3, SEP_3,
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&_randominit.randtbl[ DEG_3 + 1]
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};
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static struct _randomjunk *
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_randomjunk(void)
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{
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struct _randomjunk *rp = __randomjunk;
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if (rp == NULL) {
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rp = (struct _randomjunk *)malloc(sizeof (*rp));
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if (rp == NULL)
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return (NULL);
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*rp = _randominit;
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__randomjunk = rp;
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}
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return (rp);
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}
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/*
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* initstate:
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* Initialize the state information in the given array of n bytes for
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* future random number generation. Based on the number of bytes we
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* are given, and the break values for the different R.N.G.'s, we choose
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* the best (largest) one we can and set things up for it. srandom() is
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* then called to initialize the state information.
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* Note that on return from srandom(), we set state[-1] to be the type
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* multiplexed with the current value of the rear pointer; this is so
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* successive calls to initstate() won't lose this information and will
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* be able to restart with setstate().
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* Note: the first thing we do is save the current state, if any, just like
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* setstate() so that it doesn't matter when initstate is called.
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* Returns a pointer to the old state.
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*/
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char *
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initstate(
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unsigned int seed, /* seed for R. N. G. */
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char *arg_state, /* pointer to state array */
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size_t size) /* # bytes of state info */
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{
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unsigned int n;
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struct _randomjunk *rp = _randomjunk();
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char *ostate;
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if (size > UINT_MAX)
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n = UINT_MAX;
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else
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n = (unsigned int)size;
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if (rp == NULL)
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return (NULL);
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ostate = (char *)(&rp->state[ -1 ]);
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if (rp->rand_type == TYPE_0) rp->state[ -1 ] = rp->rand_type;
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else rp->state[ -1 ] =
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(unsigned int)(MAX_TYPES*(rp->rptr - rp->state) + rp->rand_type);
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if (n < BREAK_1) {
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if (n < BREAK_0) {
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return (NULL);
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}
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rp->rand_type = TYPE_0;
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rp->rand_deg = DEG_0;
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rp->rand_sep = SEP_0;
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} else {
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if (n < BREAK_2) {
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rp->rand_type = TYPE_1;
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rp->rand_deg = DEG_1;
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rp->rand_sep = SEP_1;
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} else {
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if (n < BREAK_3) {
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rp->rand_type = TYPE_2;
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rp->rand_deg = DEG_2;
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rp->rand_sep = SEP_2;
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} else {
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if (n < BREAK_4) {
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rp->rand_type = TYPE_3;
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rp->rand_deg = DEG_3;
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rp->rand_sep = SEP_3;
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} else {
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rp->rand_type = TYPE_4;
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rp->rand_deg = DEG_4;
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rp->rand_sep = SEP_4;
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}
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}
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}
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}
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/* first location */
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rp->state = &(((unsigned int *)(uintptr_t)arg_state)[1]);
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/* must set end_ptr before srandom */
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rp->end_ptr = &rp->state[rp->rand_deg];
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srandom(seed);
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if (rp->rand_type == TYPE_0) rp->state[ -1 ] = rp->rand_type;
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else
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rp->state[-1] = (unsigned int)(MAX_TYPES*
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(rp->rptr - rp->state) + rp->rand_type);
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return (ostate);
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}
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/*
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* setstate:
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* Restore the state from the given state array.
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* Note: it is important that we also remember the locations of the pointers
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* in the current state information, and restore the locations of the pointers
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* from the old state information. This is done by multiplexing the pointer
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* location into the zeroeth word of the state information.
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* Note that due to the order in which things are done, it is OK to call
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* setstate() with the same state as the current state.
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* Returns a pointer to the old state information.
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*/
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char *
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setstate(const char *arg_state)
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{
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struct _randomjunk *rp = _randomjunk();
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unsigned int *new_state;
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unsigned int type;
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unsigned int rear;
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char *ostate;
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if (rp == NULL)
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return (NULL);
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new_state = (unsigned int *)(uintptr_t)arg_state;
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type = new_state[0]%MAX_TYPES;
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rear = new_state[0]/MAX_TYPES;
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ostate = (char *)(&rp->state[ -1 ]);
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if (rp->rand_type == TYPE_0) rp->state[ -1 ] = rp->rand_type;
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else
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rp->state[-1] = (unsigned int)(MAX_TYPES*
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(rp->rptr - rp->state) + rp->rand_type);
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switch (type) {
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case TYPE_0:
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case TYPE_1:
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case TYPE_2:
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case TYPE_3:
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case TYPE_4:
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rp->rand_type = type;
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rp->rand_deg = rp->degrees[ type ];
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rp->rand_sep = rp->seps[ type ];
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break;
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default:
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return (NULL);
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}
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rp->state = &new_state[ 1 ];
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if (rp->rand_type != TYPE_0) {
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rp->rptr = &rp->state[ rear ];
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rp->fptr = &rp->state[ (rear + rp->rand_sep)%rp->rand_deg ];
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}
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rp->end_ptr = &rp->state[ rp->rand_deg ]; /* set end_ptr too */
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return (ostate);
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}
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/*
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* random:
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* If we are using the trivial TYPE_0 R.N.G., just do the old linear
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* congruential bit. Otherwise, we do our fancy trinomial stuff, which is the
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* same in all ther other cases due to all the global variables that have been
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* set up. The basic operation is to add the number at the rear pointer into
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* the one at the front pointer. Then both pointers are advanced to the next
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* location cyclically in the table. The value returned is the sum generated,
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* reduced to 31 bits by throwing away the "least random" low bit.
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* Note: the code takes advantage of the fact that both the front and
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* rear pointers can't wrap on the same call by not testing the rear
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* pointer if the front one has wrapped.
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* Returns a 31-bit random number.
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*/
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long
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random(void)
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{
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struct _randomjunk *rp = _randomjunk();
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unsigned int i;
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if (rp == NULL)
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return (0L);
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if (rp->rand_type == TYPE_0) {
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i = rp->state[0] = (rp->state[0]*1103515245 + 12345)&0x7fffffff;
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} else {
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*rp->fptr += *rp->rptr;
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i = (*rp->fptr >> 1)&0x7fffffff; /* chucking least random bit */
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if (++rp->fptr >= rp->end_ptr) {
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rp->fptr = rp->state;
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++rp->rptr;
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} else {
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if (++rp->rptr >= rp->end_ptr) rp->rptr = rp->state;
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}
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}
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return ((long)i);
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}
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380 |
|
|
381 |
/*
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|
382 |
* srandom:
|
|
383 |
* Initialize the random number generator based on the given seed. If the
|
|
384 |
* type is the trivial no-state-information type, just remember the seed.
|
|
385 |
* Otherwise, initializes state[] based on the given "seed" via a linear
|
|
386 |
* congruential generator. Then, the pointers are set to known locations
|
|
387 |
* that are exactly rand_sep places apart. Lastly, it cycles the state
|
|
388 |
* information a given number of times to get rid of any initial dependencies
|
|
389 |
* introduced by the L.C.R.N.G.
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|
390 |
* Note that the initialization of randtbl[] for default usage relies on
|
|
391 |
* values produced by this routine.
|
|
392 |
*/
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|
393 |
|
|
394 |
void
|
|
395 |
srandom(unsigned int x)
|
|
396 |
{
|
|
397 |
struct _randomjunk *rp = _randomjunk();
|
|
398 |
unsigned int i;
|
|
399 |
|
|
400 |
if (rp == NULL)
|
|
401 |
return;
|
|
402 |
if (rp->rand_type == TYPE_0) {
|
|
403 |
rp->state[ 0 ] = x;
|
|
404 |
} else {
|
|
405 |
rp->state[ 0 ] = x;
|
|
406 |
for (i = 1; i < rp->rand_deg; i++) {
|
|
407 |
rp->state[i] = 1103515245*rp->state[i - 1] + 12345;
|
|
408 |
}
|
|
409 |
rp->fptr = &rp->state[ rp->rand_sep ];
|
|
410 |
rp->rptr = &rp->state[ 0 ];
|
|
411 |
for (i = 0; i < 10*rp->rand_deg; i++) (void)random();
|
|
412 |
}
|
|
413 |
}
|