OpenSolaris Launch

1 files changed, 384 insertions, 0 deletions

diff --git a/usr/src/lib/libbc/libc/gen/common/random.c b/usr/src/lib/libbc/libc/gen/common/random.c
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+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License, Version 1.0 only
+ * (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 (c) 1999 by Sun Microsystems, Inc.
+ * All rights reserved.
+ */
+
+#pragma ident	"%Z%%M%	%I%	%E% SMI"
+	/* from UCB 4.2 83/01/02 */
+
+#include	<stdio.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 struct _randomjunk {
+	int	degrees[MAX_TYPES];
+	int	seps[MAX_TYPES];
+	long	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).
+ */
+	long	*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.
+ */
+	long	*state;
+	int	rand_type, rand_deg, rand_sep;
+	long	*end_ptr;
+} *__randomjunk, *_randomjunk(), _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,
+	(long)0x9a319039, (long)0x32d9c024, (long)0x9b663182, (long)0x5da1f342,
+	(long)0xde3b81e0, (long)0xdf0a6fb5, (long)0xf103bc02, (long)0x48f340fb,
+	(long)0x7449e56b, (long)0xbeb1dbb0, (long)0xab5c5918, (long)0x946554fd,
+	(long)0x8c2e680f, (long)0xeb3d799f, (long)0xb11ee0b7, (long)0x2d436b86,
+	(long)0xda672e2a, (long)0x1588ca88, (long)0xe369735d, (long)0x904f35f7,
+	(long)0xd7158fd6, (long)0x6fa6f051, (long)0x616e6b96, (long)0xac94efdc,
+	(long)0x36413f93, (long)0xc622c298, (long)0xf5a42ab8, (long)0x8a88d77b,
+	(long)0xf5ad9d0e, (long)0x8999220b, (long)0x27fb47b9 },
+	&_randominit.randtbl[ SEP_3 + 1 ],
+	&_randominit.randtbl[1],
+	&_randominit.randtbl[1],
+	TYPE_3, DEG_3, SEP_3,
+	&_randominit.randtbl[ DEG_3 + 1]
+};
+
+long random();
+extern char *malloc();
+
+static struct _randomjunk *
+_randomjunk()
+{
+	register struct _randomjunk *rp = __randomjunk;
+
+	if (rp == 0) {
+		rp = (struct _randomjunk *)malloc(sizeof (*rp));
+		if (rp == 0)
+			return (0);
+		*rp = _randominit;
+		__randomjunk = rp;
+	}
+	return (rp);
+}
+
+/*
+ * 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.
+ */
+
+srandom(x)
+	unsigned	x;
+{
+	register struct _randomjunk *rp = _randomjunk();
+	register  int		i;
+
+	if (rp == 0)
+		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++)
+		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.
+ */
+
+char  *
+initstate(seed, arg_state, n)
+	unsigned	seed;			/* seed for R. N. G. */
+	char		*arg_state;		/* pointer to state array */
+	int		n;			/* # bytes of state info */
+{
+	register struct _randomjunk *rp = _randomjunk();
+	register  char		*ostate;
+
+	if (rp == 0)
+		return (0);
+	ostate = (char *)(&rp->state[-1]);
+
+	if (rp->rand_type  ==  TYPE_0)  rp->state[-1] = rp->rand_type;
+	else  rp->state[-1] =
+	    MAX_TYPES*(rp->rptr - rp->state) + rp->rand_type;
+	if (n < BREAK_0) {
+		fprintf(stderr,
+	"initstate: state array too small, ignored; minimum size is %d bytes\n",
+			BREAK_0);
+		return (0);
+	} else if (n < BREAK_1) {
+		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;
+	}
+	rp->state = &((long *)arg_state)[1];	/* first location */
+	rp->end_ptr = &rp->state[rp->rand_deg];	/* set end_ptr before srandom */
+	srandom(seed);
+	rp->state[-1] = (rp->rand_type == TYPE_0) ? rp->rand_type
+			: 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(arg_state)
+	char		*arg_state;
+{
+	register struct _randomjunk *rp = _randomjunk();
+	register  long		*new_state;
+	register  int		type;
+	register  int		rear;
+	char			*ostate;
+
+	if (rp == 0)
+		return (0);
+	new_state = (long *)arg_state;
+	type = new_state[0] % MAX_TYPES;
+	rear = new_state[0] / MAX_TYPES;
+	ostate = (char *)(&rp->state[-1]);
+
+	rp->state[-1] = (rp->rand_type == TYPE_0) ? rp->rand_type
+			: 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:
+		fprintf(stderr, "setstate: invalid state info; not changed.\n");
+	}
+	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()
+{
+	register struct _randomjunk *rp = _randomjunk();
+	long		i;
+
+	if (rp == 0)
+		return (0);
+	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 (i);
+}