CbC/CbC_gcc: libiberty/random.c comparison

comparison libiberty/random.c @ 0:a06113de4d67

first commit

author	kent <kent@cr.ie.u-ryukyu.ac.jp>
date	Fri, 17 Jul 2009 14:47:48 +0900
parents
children	f6334be47118

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+:a06113de4d67
+/*
+* Copyright (c) 1983 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. [rescinded 22 July 1999]
+* 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.
+*/
+/*
+* This is derived from the Berkeley source:
+*	@(#)random.c	5.5 (Berkeley) 7/6/88
+* It was reworked for the GNU C Library by Roland McGrath.
+*/
+/*
+@deftypefn Supplement {long int} random (void)
+@deftypefnx Supplement void srandom (unsigned int @var{seed})
+@deftypefnx Supplement void* initstate (unsigned int @var{seed}, void *@var{arg_state}, unsigned long @var{n})
+@deftypefnx Supplement void* setstate (void *@var{arg_state})
+Random number functions.  @code{random} returns a random number in the
+range 0 to @code{LONG_MAX}.  @code{srandom} initializes the random
+number generator to some starting point determined by @var{seed}
+(else, the values returned by @code{random} are always the same for each
+run of the program).  @code{initstate} and @code{setstate} allow fine-grained
+control over the state of the random number generator.
+@end deftypefn
+*/
+#include <errno.h>
+#if 0
+#include <ansidecl.h>
+#include <limits.h>
+#include <stddef.h>
+#include <stdlib.h>
+#else
+#define	ULONG_MAX  ((unsigned long)(~0L))     /* 0xFFFFFFFF for 32-bits */
+#define	LONG_MAX   ((long)(ULONG_MAX >> 1))   /* 0x7FFFFFFF for 32-bits*/
+#ifdef __STDC__
+#  define PTR void *
+#  ifndef NULL
+#    define NULL (void *) 0
+#  endif
+#else
+#  define PTR char *
+#  ifndef NULL
+#    define NULL (void *) 0
+#  endif
+#endif
+#endif
+long int random (void);
+/* 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() function 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 thi
+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
+separation between the two lower order coefficients of the trinomial.  */
+/* Linear congruential.  */
+#define	TYPE_0		0
+#define	BREAK_0		8
+#define	DEG_0		0
+#define	SEP_0		0
+/* x**7 + x**3 + 1.  */
+#define	TYPE_1		1
+#define	BREAK_1		32
+#define	DEG_1		7
+#define	SEP_1		3
+/* x**15 + x + 1.  */
+#define	TYPE_2		2
+#define	BREAK_2		64
+#define	DEG_2		15
+#define	SEP_2		1
+/* x**31 + x**3 + 1.  */
+#define	TYPE_3		3
+#define	BREAK_3		128
+#define	DEG_3		31
+#define	SEP_3		3
+/* x**63 + x + 1.  */
+#define	TYPE_4		4
+#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 int degrees[MAX_TYPES] = { DEG_0, DEG_1, DEG_2, DEG_3, DEG_4 };
+static 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.  */
+static long int 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 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 int *fptr = &randtbl[SEP_3 + 1];
+static long 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 long int *state = &randtbl[1];
+static int rand_type = TYPE_3;
+static int rand_deg = DEG_3;
+static int rand_sep = SEP_3;
+static long int *end_ptr = &randtbl[sizeof(randtbl) / sizeof(randtbl[0])];
+/* 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)
+{
+state[0] = x;
+if (rand_type != TYPE_0)
+{
+register long int i;
+for (i = 1; i < rand_deg; ++i)
+	state[i] = (1103515145 * state[i - 1]) + 12345;
+fptr = &state[rand_sep];
+rptr = &state[0];
+for (i = 0; i < 10 * rand_deg; ++i)
+	random();
+}
+}
+/* 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.  */
+PTR
+initstate (unsigned int seed, PTR arg_state, unsigned long n)
+{
+PTR ostate = (PTR) &state[-1];
+if (rand_type == TYPE_0)
+state[-1] = rand_type;
+else
+state[-1] = (MAX_TYPES * (rptr - state)) + rand_type;
+if (n < BREAK_1)
+{
+if (n < BREAK_0)
+	{
+	  errno = EINVAL;
+	  return NULL;
+	}
+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 int *) arg_state)[1];	/* First location.  */
+/* Must set END_PTR before srandom.  */
+end_ptr = &state[rand_deg];
+srandom(seed);
+if (rand_type == TYPE_0)
+state[-1] = rand_type;
+else
+state[-1] = (MAX_TYPES * (rptr - state)) + rand_type;
+return ostate;
+}
+/* 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.  */
+PTR
+setstate (PTR arg_state)
+{
+register long int *new_state = (long int *) arg_state;
+register int type = new_state[0] % MAX_TYPES;
+register int rear = new_state[0] / MAX_TYPES;
+PTR ostate = (PTR) &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:
+/* State info munged.  */
+errno = EINVAL;
+return NULL;
+}
+state = &new_state[1];
+if (rand_type != TYPE_0)
+{
+rptr = &state[rear];
+fptr = &state[(rear + rand_sep) % rand_deg];
+}
+/* Set end_ptr too.  */
+end_ptr = &state[rand_deg];
+return ostate;
+}
+/* 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 int
+random (void)
+{
+if (rand_type == TYPE_0)
+{
+state[0] = ((state[0] * 1103515245) + 12345) & LONG_MAX;
+return state[0];
+}
+else
+{
+long int i;
+*fptr += *rptr;
+/* Chucking least random bit.  */
+i = (*fptr >> 1) & LONG_MAX;
+++fptr;
+if (fptr >= end_ptr)
+	{
+	  fptr = state;
+	  ++rptr;
+	}
+else
+	{
+	  ++rptr;
+	  if (rptr >= end_ptr)
+	    rptr = state;
+	}
+return i;
+}
+}

Mercurial > hg > CbC > CbC_gcc

comparison libiberty/random.c @ 0:a06113de4d67