/*
|
/*
|
Copyright (C) 1995, 2004 Free Software Foundation
|
Copyright (C) 1995, 2004 Free Software Foundation
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
The GNU C Library is free software; you can redistribute it and/or
|
modify it under the terms of the GNU Lesser General Public
|
modify it under the terms of the GNU Lesser General Public
|
License as published by the Free Software Foundation; either
|
License as published by the Free Software Foundation; either
|
version 2.1 of the License, or (at your option) any later version.
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
The GNU C Library is distributed in the hope that it will be useful,
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
Lesser General Public License for more details.
|
Lesser General Public License for more details.
|
|
|
You should have received a copy of the GNU Lesser General Public
|
You should have received a copy of the GNU Lesser General Public
|
License along with the GNU C Library; if not, write to the Free
|
License along with the GNU C Library; if not, write to the Free
|
Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
|
Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
|
02110-1301 USA. */
|
02110-1301 USA. */
|
|
|
/*
|
/*
|
Copyright (C) 1983 Regents of the University of California.
|
Copyright (C) 1983 Regents of the University of California.
|
All rights reserved.
|
All rights reserved.
|
|
|
Redistribution and use in source and binary forms, with or without
|
Redistribution and use in source and binary forms, with or without
|
modification, are permitted provided that the following conditions
|
modification, are permitted provided that the following conditions
|
are met:
|
are met:
|
|
|
1. Redistributions of source code must retain the above copyright
|
1. Redistributions of source code must retain the above copyright
|
notice, this list of conditions and the following disclaimer.
|
notice, this list of conditions and the following disclaimer.
|
2. Redistributions in binary form must reproduce the above copyright
|
2. Redistributions in binary form must reproduce the above copyright
|
notice, this list of conditions and the following disclaimer in the
|
notice, this list of conditions and the following disclaimer in the
|
documentation and/or other materials provided with the distribution.
|
documentation and/or other materials provided with the distribution.
|
4. Neither the name of the University nor the names of 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
|
may be used to endorse or promote products derived from this software
|
without specific prior written permission.
|
without specific prior written permission.
|
|
|
THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
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
|
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
SUCH DAMAGE.*/
|
SUCH DAMAGE.*/
|
|
|
/*
|
/*
|
* This is derived from the Berkeley source:
|
* This is derived from the Berkeley source:
|
* @(#)random.c 5.5 (Berkeley) 7/6/88
|
* @(#)random.c 5.5 (Berkeley) 7/6/88
|
* It was reworked for the GNU C Library by Roland McGrath.
|
* It was reworked for the GNU C Library by Roland McGrath.
|
* Rewritten to be reentrant by Ulrich Drepper, 1995
|
* Rewritten to be reentrant by Ulrich Drepper, 1995
|
*/
|
*/
|
|
|
#include <limits.h>
|
#include <limits.h>
|
#include <stdlib.h>
|
#include <stdlib.h>
|
#include "generate-random.h"
|
#include "generate-random.h"
|
|
|
|
|
/* An improved random number generation package. In addition to the standard
|
/* An improved random number generation package. In addition to the standard
|
rand()/srand() like interface, this package also has a special state info
|
rand()/srand() like interface, this package also has a special state info
|
interface. The initstate() routine is called with a seed, an array of
|
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
|
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
|
then initialized to contain information for random number generation with
|
that much state information. Good sizes for the amount of state
|
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
|
information are 32, 64, 128, and 256 bytes. The state can be switched by
|
calling the setstate() function with the same array as was initialized
|
calling the setstate() function with the same array as was initialized
|
with initstate(). By default, the package runs with 128 bytes of state
|
with initstate(). By default, the package runs with 128 bytes of state
|
information and generates far better random numbers than a linear
|
information and generates far better random numbers than a linear
|
congruential generator. If the amount of state information is less than
|
congruential generator. If the amount of state information is less than
|
32 bytes, a simple linear congruential R.N.G. is used. Internally, the
|
32 bytes, a simple linear congruential R.N.G. is used. Internally, the
|
state information is treated as an array of longs; the zeroth element of
|
state information is treated as an array of longs; the zeroth element of
|
the array is the type of R.N.G. being used (small integer); the remainder
|
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
|
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
|
state information will give 7 longs worth of state information, which will
|
allow a degree seven polynomial. (Note: The zeroth word of state
|
allow a degree seven polynomial. (Note: The zeroth word of state
|
information also has some other information stored in it; see setstate
|
information also has some other information stored in it; see setstate
|
for details). The random number generation technique is a linear feedback
|
for details). The random number generation technique is a linear feedback
|
shift register approach, employing trinomials (since there are fewer terms
|
shift register approach, employing trinomials (since there are fewer terms
|
to sum up that way). In this approach, the least significant bit of all
|
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,
|
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
|
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).
|
being used, assuming that the polynomial is irreducible and primitive).
|
The higher order bits will have longer periods, since their values are
|
The higher order bits will have longer periods, since their values are
|
also influenced by pseudo-random carries out of the lower bits. The
|
also influenced by pseudo-random carries out of the lower bits. The
|
total period of the generator is approximately deg*(2**deg - 1); thus
|
total period of the generator is approximately deg*(2**deg - 1); thus
|
doubling the amount of state information has a vast influence on the
|
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
|
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
|
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
|
dominant factor. With deg equal to seven, the period is actually much
|
longer than the 7*(2**7 - 1) predicted by this formula. */
|
longer than the 7*(2**7 - 1) predicted by this formula. */
|
|
|
|
|
|
|
/* For each of the currently supported random number generators, we have a
|
/* 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
|
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
|
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 polynomial (actually a trinomial) that the R.N.G. is based on, and
|
separation between the two lower order coefficients of the trinomial. */
|
separation between the two lower order coefficients of the trinomial. */
|
|
|
/* Linear congruential. */
|
/* Linear congruential. */
|
#define TYPE_0 0
|
#define TYPE_0 0
|
#define BREAK_0 8
|
#define BREAK_0 8
|
#define DEG_0 0
|
#define DEG_0 0
|
#define SEP_0 0
|
#define SEP_0 0
|
|
|
/* x**7 + x**3 + 1. */
|
/* x**7 + x**3 + 1. */
|
#define TYPE_1 1
|
#define TYPE_1 1
|
#define BREAK_1 32
|
#define BREAK_1 32
|
#define DEG_1 7
|
#define DEG_1 7
|
#define SEP_1 3
|
#define SEP_1 3
|
|
|
/* x**15 + x + 1. */
|
/* x**15 + x + 1. */
|
#define TYPE_2 2
|
#define TYPE_2 2
|
#define BREAK_2 64
|
#define BREAK_2 64
|
#define DEG_2 15
|
#define DEG_2 15
|
#define SEP_2 1
|
#define SEP_2 1
|
|
|
/* x**31 + x**3 + 1. */
|
/* x**31 + x**3 + 1. */
|
#define TYPE_3 3
|
#define TYPE_3 3
|
#define BREAK_3 128
|
#define BREAK_3 128
|
#define DEG_3 31
|
#define DEG_3 31
|
#define SEP_3 3
|
#define SEP_3 3
|
|
|
/* x**63 + x + 1. */
|
/* x**63 + x + 1. */
|
#define TYPE_4 4
|
#define TYPE_4 4
|
#define BREAK_4 256
|
#define BREAK_4 256
|
#define DEG_4 63
|
#define DEG_4 63
|
#define SEP_4 1
|
#define SEP_4 1
|
|
|
|
|
/* Array versions of the above information to make code run faster.
|
/* Array versions of the above information to make code run faster.
|
Relies on fact that TYPE_i == i. */
|
Relies on fact that TYPE_i == i. */
|
|
|
#define MAX_TYPES 5 /* Max number of types above. */
|
#define MAX_TYPES 5 /* Max number of types above. */
|
|
|
struct random_poly_info
|
struct random_poly_info
|
{
|
{
|
int seps[MAX_TYPES];
|
int seps[MAX_TYPES];
|
int degrees[MAX_TYPES];
|
int degrees[MAX_TYPES];
|
};
|
};
|
|
|
static const struct random_poly_info random_poly_info =
|
static const struct random_poly_info random_poly_info =
|
{
|
{
|
{ SEP_0, SEP_1, SEP_2, SEP_3, SEP_4 },
|
{ SEP_0, SEP_1, SEP_2, SEP_3, SEP_4 },
|
{ DEG_0, DEG_1, DEG_2, DEG_3, DEG_4 }
|
{ DEG_0, DEG_1, DEG_2, DEG_3, DEG_4 }
|
};
|
};
|
|
|
|
|
|
|
|
|
/* Initialize the random number generator based on the given seed. If the
|
/* Initialize the random number generator based on the given seed. If the
|
type is the trivial no-state-information type, just remember the seed.
|
type is the trivial no-state-information type, just remember the seed.
|
Otherwise, initializes state[] based on the given "seed" via a linear
|
Otherwise, initializes state[] based on the given "seed" via a linear
|
congruential generator. Then, the pointers are set to known locations
|
congruential generator. Then, the pointers are set to known locations
|
that are exactly rand_sep places apart. Lastly, it cycles the state
|
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
|
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[]
|
introduced by the L.C.R.N.G. Note that the initialization of randtbl[]
|
for default usage relies on values produced by this routine. */
|
for default usage relies on values produced by this routine. */
|
int
|
int
|
generate_srandom_r (unsigned int seed, struct generate_random_data *buf)
|
generate_srandom_r (unsigned int seed, struct generate_random_data *buf)
|
{
|
{
|
int type;
|
int type;
|
int *state;
|
int *state;
|
long int i;
|
long int i;
|
long int word;
|
long int word;
|
int *dst;
|
int *dst;
|
int kc;
|
int kc;
|
|
|
if (buf == NULL)
|
if (buf == NULL)
|
goto fail;
|
goto fail;
|
type = buf->rand_type;
|
type = buf->rand_type;
|
if ((unsigned int) type >= MAX_TYPES)
|
if ((unsigned int) type >= MAX_TYPES)
|
goto fail;
|
goto fail;
|
|
|
state = buf->state;
|
state = buf->state;
|
/* We must make sure the seed is not 0. Take arbitrarily 1 in this case. */
|
/* We must make sure the seed is not 0. Take arbitrarily 1 in this case. */
|
if (seed == 0)
|
if (seed == 0)
|
seed = 1;
|
seed = 1;
|
state[0] = seed;
|
state[0] = seed;
|
if (type == TYPE_0)
|
if (type == TYPE_0)
|
goto done;
|
goto done;
|
|
|
dst = state;
|
dst = state;
|
word = seed;
|
word = seed;
|
kc = buf->rand_deg;
|
kc = buf->rand_deg;
|
for (i = 1; i < kc; ++i)
|
for (i = 1; i < kc; ++i)
|
{
|
{
|
/* This does:
|
/* This does:
|
state[i] = (16807 * state[i - 1]) % 2147483647;
|
state[i] = (16807 * state[i - 1]) % 2147483647;
|
but avoids overflowing 31 bits. */
|
but avoids overflowing 31 bits. */
|
long int hi = word / 127773;
|
long int hi = word / 127773;
|
long int lo = word % 127773;
|
long int lo = word % 127773;
|
word = 16807 * lo - 2836 * hi;
|
word = 16807 * lo - 2836 * hi;
|
if (word < 0)
|
if (word < 0)
|
word += 2147483647;
|
word += 2147483647;
|
*++dst = word;
|
*++dst = word;
|
}
|
}
|
|
|
buf->fptr = &state[buf->rand_sep];
|
buf->fptr = &state[buf->rand_sep];
|
buf->rptr = &state[0];
|
buf->rptr = &state[0];
|
kc *= 10;
|
kc *= 10;
|
while (--kc >= 0)
|
while (--kc >= 0)
|
{
|
{
|
int discard;
|
int discard;
|
(void) generate_random_r (buf, &discard);
|
(void) generate_random_r (buf, &discard);
|
}
|
}
|
|
|
done:
|
done:
|
return 0;
|
return 0;
|
|
|
fail:
|
fail:
|
return -1;
|
return -1;
|
}
|
}
|
|
|
/* Initialize the state information in the given array of N bytes for
|
/* Initialize the state information in the given array of N bytes for
|
future random number generation. Based on the number of bytes we
|
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
|
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
|
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
|
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
|
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
|
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.
|
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
|
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.
|
setstate so that it doesn't matter when initstate is called.
|
Returns a pointer to the old state. */
|
Returns a pointer to the old state. */
|
int
|
int
|
generate_initstate_r (unsigned int seed, char *arg_state, size_t n,
|
generate_initstate_r (unsigned int seed, char *arg_state, size_t n,
|
struct generate_random_data *buf)
|
struct generate_random_data *buf)
|
{
|
{
|
int type;
|
int type;
|
int degree;
|
int degree;
|
int separation;
|
int separation;
|
int *state;
|
int *state;
|
|
|
if (buf == NULL)
|
if (buf == NULL)
|
goto fail;
|
goto fail;
|
|
|
if (n >= BREAK_3)
|
if (n >= BREAK_3)
|
type = n < BREAK_4 ? TYPE_3 : TYPE_4;
|
type = n < BREAK_4 ? TYPE_3 : TYPE_4;
|
else if (n < BREAK_1)
|
else if (n < BREAK_1)
|
{
|
{
|
if (n < BREAK_0)
|
if (n < BREAK_0)
|
{
|
{
|
goto fail;
|
goto fail;
|
}
|
}
|
type = TYPE_0;
|
type = TYPE_0;
|
}
|
}
|
else
|
else
|
type = n < BREAK_2 ? TYPE_1 : TYPE_2;
|
type = n < BREAK_2 ? TYPE_1 : TYPE_2;
|
|
|
degree = random_poly_info.degrees[type];
|
degree = random_poly_info.degrees[type];
|
separation = random_poly_info.seps[type];
|
separation = random_poly_info.seps[type];
|
|
|
buf->rand_type = type;
|
buf->rand_type = type;
|
buf->rand_sep = separation;
|
buf->rand_sep = separation;
|
buf->rand_deg = degree;
|
buf->rand_deg = degree;
|
state = &((int *) arg_state)[1]; /* First location. */
|
state = &((int *) arg_state)[1]; /* First location. */
|
/* Must set END_PTR before srandom. */
|
/* Must set END_PTR before srandom. */
|
buf->end_ptr = &state[degree];
|
buf->end_ptr = &state[degree];
|
|
|
buf->state = state;
|
buf->state = state;
|
|
|
generate_srandom_r (seed, buf);
|
generate_srandom_r (seed, buf);
|
|
|
state[-1] = TYPE_0;
|
state[-1] = TYPE_0;
|
if (type != TYPE_0)
|
if (type != TYPE_0)
|
state[-1] = (buf->rptr - state) * MAX_TYPES + type;
|
state[-1] = (buf->rptr - state) * MAX_TYPES + type;
|
|
|
return 0;
|
return 0;
|
|
|
fail:
|
fail:
|
return -1;
|
return -1;
|
}
|
}
|
|
|
/* Restore the state from the given state array.
|
/* Restore the state from the given state array.
|
Note: It is important that we also remember the locations of the pointers
|
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
|
in the current state information, and restore the locations of the pointers
|
from the old state information. This is done by multiplexing the pointer
|
from the old state information. This is done by multiplexing the pointer
|
location into the zeroth word of the state information. Note that due
|
location into the zeroth word of the state information. Note that due
|
to the order in which things are done, it is OK to call setstate with the
|
to the order in which things are done, it is OK to call setstate with the
|
same state as the current state
|
same state as the current state
|
Returns a pointer to the old state information. */
|
Returns a pointer to the old state information. */
|
int
|
int
|
generate_setstate_r (char *arg_state, struct generate_random_data *buf)
|
generate_setstate_r (char *arg_state, struct generate_random_data *buf)
|
{
|
{
|
int *new_state = 1 + (int *) arg_state;
|
int *new_state = 1 + (int *) arg_state;
|
int type;
|
int type;
|
int old_type;
|
int old_type;
|
int *old_state;
|
int *old_state;
|
int degree;
|
int degree;
|
int separation;
|
int separation;
|
|
|
if (arg_state == NULL || buf == NULL)
|
if (arg_state == NULL || buf == NULL)
|
goto fail;
|
goto fail;
|
|
|
old_type = buf->rand_type;
|
old_type = buf->rand_type;
|
old_state = buf->state;
|
old_state = buf->state;
|
if (old_type == TYPE_0)
|
if (old_type == TYPE_0)
|
old_state[-1] = TYPE_0;
|
old_state[-1] = TYPE_0;
|
else
|
else
|
old_state[-1] = (MAX_TYPES * (buf->rptr - old_state)) + old_type;
|
old_state[-1] = (MAX_TYPES * (buf->rptr - old_state)) + old_type;
|
|
|
type = new_state[-1] % MAX_TYPES;
|
type = new_state[-1] % MAX_TYPES;
|
if (type < TYPE_0 || type > TYPE_4)
|
if (type < TYPE_0 || type > TYPE_4)
|
goto fail;
|
goto fail;
|
|
|
buf->rand_deg = degree = random_poly_info.degrees[type];
|
buf->rand_deg = degree = random_poly_info.degrees[type];
|
buf->rand_sep = separation = random_poly_info.seps[type];
|
buf->rand_sep = separation = random_poly_info.seps[type];
|
buf->rand_type = type;
|
buf->rand_type = type;
|
|
|
if (type != TYPE_0)
|
if (type != TYPE_0)
|
{
|
{
|
int rear = new_state[-1] / MAX_TYPES;
|
int rear = new_state[-1] / MAX_TYPES;
|
buf->rptr = &new_state[rear];
|
buf->rptr = &new_state[rear];
|
buf->fptr = &new_state[(rear + separation) % degree];
|
buf->fptr = &new_state[(rear + separation) % degree];
|
}
|
}
|
buf->state = new_state;
|
buf->state = new_state;
|
/* Set end_ptr too. */
|
/* Set end_ptr too. */
|
buf->end_ptr = &new_state[degree];
|
buf->end_ptr = &new_state[degree];
|
|
|
return 0;
|
return 0;
|
|
|
fail:
|
fail:
|
return -1;
|
return -1;
|
}
|
}
|
|
|
/* If we are using the trivial TYPE_0 R.N.G., just do the old linear
|
/* 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
|
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
|
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
|
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
|
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,
|
location cyclically in the table. The value returned is the sum generated,
|
reduced to 31 bits by throwing away the "least random" low bit.
|
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
|
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
|
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. */
|
pointer if the front one has wrapped. Returns a 31-bit random number. */
|
|
|
int
|
int
|
generate_random_r (struct generate_random_data *buf, int *result)
|
generate_random_r (struct generate_random_data *buf, int *result)
|
{
|
{
|
int *state;
|
int *state;
|
|
|
if (buf == NULL || result == NULL)
|
if (buf == NULL || result == NULL)
|
goto fail;
|
goto fail;
|
|
|
state = buf->state;
|
state = buf->state;
|
|
|
if (buf->rand_type == TYPE_0)
|
if (buf->rand_type == TYPE_0)
|
{
|
{
|
int val = state[0];
|
int val = state[0];
|
val = ((state[0] * 1103515245) + 12345) & 0x7fffffff;
|
val = ((state[0] * 1103515245) + 12345) & 0x7fffffff;
|
state[0] = val;
|
state[0] = val;
|
*result = val;
|
*result = val;
|
}
|
}
|
else
|
else
|
{
|
{
|
int *fptr = buf->fptr;
|
int *fptr = buf->fptr;
|
int *rptr = buf->rptr;
|
int *rptr = buf->rptr;
|
int *end_ptr = buf->end_ptr;
|
int *end_ptr = buf->end_ptr;
|
int val;
|
int val;
|
|
|
val = *fptr += *rptr;
|
val = *fptr += *rptr;
|
/* Chucking least random bit. */
|
/* Chucking least random bit. */
|
*result = (val >> 1) & 0x7fffffff;
|
*result = (val >> 1) & 0x7fffffff;
|
++fptr;
|
++fptr;
|
if (fptr >= end_ptr)
|
if (fptr >= end_ptr)
|
{
|
{
|
fptr = state;
|
fptr = state;
|
++rptr;
|
++rptr;
|
}
|
}
|
else
|
else
|
{
|
{
|
++rptr;
|
++rptr;
|
if (rptr >= end_ptr)
|
if (rptr >= end_ptr)
|
rptr = state;
|
rptr = state;
|
}
|
}
|
buf->fptr = fptr;
|
buf->fptr = fptr;
|
buf->rptr = rptr;
|
buf->rptr = rptr;
|
}
|
}
|
return 0;
|
return 0;
|
|
|
fail:
|
fail:
|
return -1;
|
return -1;
|
}
|
}
|
|
|
