gnu / gcc / a6d3012b274f38b20e2a57162106f625746af6c6 / . / gcc / testsuite / objc.dg / gnu-encoding / generate-random_r.c

/* | |

Copyright (C) 1995, 2004 Free Software Foundation | |

The GNU C Library is free software; you can redistribute it and/or | |

modify it under the terms of the GNU Lesser General Public | |

License as published by the Free Software Foundation; either | |

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, | |

but WITHOUT ANY WARRANTY; without even the implied warranty of | |

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |

Lesser General Public License for more details. | |

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 | |

Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA | |

02110-1301 USA. */ | |

/* | |

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. | |

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. | |

* Rewritten to be reentrant by Ulrich Drepper, 1995 | |

*/ | |

#include <limits.h> | |

#include <stdlib.h> | |

#include "generate-random.h" | |

/* 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 initialized | |

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 zeroth 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 zeroth 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 | |

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. */ | |

struct random_poly_info | |

{ | |

int seps[MAX_TYPES]; | |

int degrees[MAX_TYPES]; | |

}; | |

static const struct random_poly_info random_poly_info = | |

{ | |

{ SEP_0, SEP_1, SEP_2, SEP_3, SEP_4 }, | |

{ DEG_0, DEG_1, DEG_2, DEG_3, DEG_4 } | |

}; | |

/* 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. */ | |

int | |

generate_srandom_r (unsigned int seed, struct generate_random_data *buf) | |

{ | |

int type; | |

int *state; | |

long int i; | |

long int word; | |

int *dst; | |

int kc; | |

if (buf == NULL) | |

goto fail; | |

type = buf->rand_type; | |

if ((unsigned int) type >= MAX_TYPES) | |

goto fail; | |

state = buf->state; | |

/* We must make sure the seed is not 0. Take arbitrarily 1 in this case. */ | |

if (seed == 0) | |

seed = 1; | |

state[0] = seed; | |

if (type == TYPE_0) | |

goto done; | |

dst = state; | |

word = seed; | |

kc = buf->rand_deg; | |

for (i = 1; i < kc; ++i) | |

{ | |

/* This does: | |

state[i] = (16807 * state[i - 1]) % 2147483647; | |

but avoids overflowing 31 bits. */ | |

long int hi = word / 127773; | |

long int lo = word % 127773; | |

word = 16807 * lo - 2836 * hi; | |

if (word < 0) | |

word += 2147483647; | |

*++dst = word; | |

} | |

buf->fptr = &state[buf->rand_sep]; | |

buf->rptr = &state[0]; | |

kc *= 10; | |

while (--kc >= 0) | |

{ | |

int discard; | |

(void) generate_random_r (buf, &discard); | |

} | |

done: | |

return 0; | |

fail: | |

return -1; | |

} | |

/* 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. */ | |

int | |

generate_initstate_r (unsigned int seed, char *arg_state, size_t n, | |

struct generate_random_data *buf) | |

{ | |

int type; | |

int degree; | |

int separation; | |

int *state; | |

if (buf == NULL) | |

goto fail; | |

if (n >= BREAK_3) | |

type = n < BREAK_4 ? TYPE_3 : TYPE_4; | |

else if (n < BREAK_1) | |

{ | |

if (n < BREAK_0) | |

{ | |

goto fail; | |

} | |

type = TYPE_0; | |

} | |

else | |

type = n < BREAK_2 ? TYPE_1 : TYPE_2; | |

degree = random_poly_info.degrees[type]; | |

separation = random_poly_info.seps[type]; | |

buf->rand_type = type; | |

buf->rand_sep = separation; | |

buf->rand_deg = degree; | |

state = &((int *) arg_state)[1]; /* First location. */ | |

/* Must set END_PTR before srandom. */ | |

buf->end_ptr = &state[degree]; | |

buf->state = state; | |

generate_srandom_r (seed, buf); | |

state[-1] = TYPE_0; | |

if (type != TYPE_0) | |

state[-1] = (buf->rptr - state) * MAX_TYPES + type; | |

return 0; | |

fail: | |

return -1; | |

} | |

/* 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 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 | |

same state as the current state | |

Returns a pointer to the old state information. */ | |

int | |

generate_setstate_r (char *arg_state, struct generate_random_data *buf) | |

{ | |

int *new_state = 1 + (int *) arg_state; | |

int type; | |

int old_type; | |

int *old_state; | |

int degree; | |

int separation; | |

if (arg_state == NULL || buf == NULL) | |

goto fail; | |

old_type = buf->rand_type; | |

old_state = buf->state; | |

if (old_type == TYPE_0) | |

old_state[-1] = TYPE_0; | |

else | |

old_state[-1] = (MAX_TYPES * (buf->rptr - old_state)) + old_type; | |

type = new_state[-1] % MAX_TYPES; | |

if (type < TYPE_0 || type > TYPE_4) | |

goto fail; | |

buf->rand_deg = degree = random_poly_info.degrees[type]; | |

buf->rand_sep = separation = random_poly_info.seps[type]; | |

buf->rand_type = type; | |

if (type != TYPE_0) | |

{ | |

int rear = new_state[-1] / MAX_TYPES; | |

buf->rptr = &new_state[rear]; | |

buf->fptr = &new_state[(rear + separation) % degree]; | |

} | |

buf->state = new_state; | |

/* Set end_ptr too. */ | |

buf->end_ptr = &new_state[degree]; | |

return 0; | |

fail: | |

return -1; | |

} | |

/* 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. */ | |

int | |

generate_random_r (struct generate_random_data *buf, int *result) | |

{ | |

int *state; | |

if (buf == NULL || result == NULL) | |

goto fail; | |

state = buf->state; | |

if (buf->rand_type == TYPE_0) | |

{ | |

int val = state[0]; | |

val = ((state[0] * 1103515245) + 12345) & 0x7fffffff; | |

state[0] = val; | |

*result = val; | |

} | |

else | |

{ | |

int *fptr = buf->fptr; | |

int *rptr = buf->rptr; | |

int *end_ptr = buf->end_ptr; | |

int val; | |

val = *fptr += *rptr; | |

/* Chucking least random bit. */ | |

*result = (val >> 1) & 0x7fffffff; | |

++fptr; | |

if (fptr >= end_ptr) | |

{ | |

fptr = state; | |

++rptr; | |

} | |

else | |

{ | |

++rptr; | |

if (rptr >= end_ptr) | |

rptr = state; | |

} | |

buf->fptr = fptr; | |

buf->rptr = rptr; | |

} | |

return 0; | |

fail: | |

return -1; | |

} |