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glib2.0/glib/grand.c

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/* GLIB - Library of useful routines for C programming
* Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*
* This 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.
*
* This 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 this library; if not, see <http://www.gnu.org/licenses/>.
*/
/* Originally developed and coded by Makoto Matsumoto and Takuji
* Nishimura. Please mail <matumoto@math.keio.ac.jp>, if you're using
* code from this file in your own programs or libraries.
* Further information on the Mersenne Twister can be found at
* http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html
* This code was adapted to glib by Sebastian Wilhelmi.
*/
/*
* Modified by the GLib Team and others 1997-2000. See the AUTHORS
* file for a list of people on the GLib Team. See the ChangeLog
* files for a list of changes. These files are distributed with
* GLib at ftp://ftp.gtk.org/pub/gtk/.
*/
/*
* MT safe
*/
#include "config.h"
#define _CRT_RAND_S
#include <math.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include "grand.h"
#include "genviron.h"
#include "gmain.h"
#include "gmem.h"
#include "gtestutils.h"
#include "gthread.h"
#include "gtimer.h"
#ifdef G_OS_UNIX
#include <unistd.h>
#endif
#ifdef G_OS_WIN32
#include <stdlib.h>
#include <process.h> /* For getpid() */
#endif
/**
* SECTION:random_numbers
* @title: Random Numbers
* @short_description: pseudo-random number generator
*
* The following functions allow you to use a portable, fast and good
* pseudo-random number generator (PRNG).
*
* Do not use this API for cryptographic purposes such as key
* generation, nonces, salts or one-time pads.
*
* This PRNG is suitable for non-cryptographic use such as in games
* (shuffling a card deck, generating levels), generating data for
* a test suite, etc. If you need random data for cryptographic
* purposes, it is recommended to use platform-specific APIs such
* as `/dev/random` on UNIX, or CryptGenRandom() on Windows.
*
* GRand uses the Mersenne Twister PRNG, which was originally
* developed by Makoto Matsumoto and Takuji Nishimura. Further
* information can be found at
* [this page](http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html).
*
* If you just need a random number, you simply call the g_random_*
* functions, which will create a globally used #GRand and use the
* according g_rand_* functions internally. Whenever you need a
* stream of reproducible random numbers, you better create a
* #GRand yourself and use the g_rand_* functions directly, which
* will also be slightly faster. Initializing a #GRand with a
* certain seed will produce exactly the same series of random
* numbers on all platforms. This can thus be used as a seed for
* e.g. games.
*
* The g_rand*_range functions will return high quality equally
* distributed random numbers, whereas for example the
* `(g_random_int()%max)` approach often
* doesn't yield equally distributed numbers.
*
* GLib changed the seeding algorithm for the pseudo-random number
* generator Mersenne Twister, as used by #GRand. This was necessary,
* because some seeds would yield very bad pseudo-random streams.
* Also the pseudo-random integers generated by g_rand*_int_range()
* will have a slightly better equal distribution with the new
* version of GLib.
*
* The original seeding and generation algorithms, as found in
* GLib 2.0.x, can be used instead of the new ones by setting the
* environment variable `G_RANDOM_VERSION` to the value of '2.0'.
* Use the GLib-2.0 algorithms only if you have sequences of numbers
* generated with Glib-2.0 that you need to reproduce exactly.
*/
/**
* GRand:
*
* The GRand struct is an opaque data structure. It should only be
* accessed through the g_rand_* functions.
**/
G_LOCK_DEFINE_STATIC (global_random);
/* Period parameters */
#define N 624
#define M 397
#define MATRIX_A 0x9908b0df /* constant vector a */
#define UPPER_MASK 0x80000000 /* most significant w-r bits */
#define LOWER_MASK 0x7fffffff /* least significant r bits */
/* Tempering parameters */
#define TEMPERING_MASK_B 0x9d2c5680
#define TEMPERING_MASK_C 0xefc60000
#define TEMPERING_SHIFT_U(y) (y >> 11)
#define TEMPERING_SHIFT_S(y) (y << 7)
#define TEMPERING_SHIFT_T(y) (y << 15)
#define TEMPERING_SHIFT_L(y) (y >> 18)
static guint
get_random_version (void)
{
static gsize initialized = FALSE;
static guint random_version;
if (g_once_init_enter (&initialized))
{
const gchar *version_string = g_getenv ("G_RANDOM_VERSION");
if (!version_string || version_string[0] == '\000' ||
strcmp (version_string, "2.2") == 0)
random_version = 22;
else if (strcmp (version_string, "2.0") == 0)
random_version = 20;
else
{
g_warning ("Unknown G_RANDOM_VERSION \"%s\". Using version 2.2.",
version_string);
random_version = 22;
}
g_once_init_leave (&initialized, TRUE);
}
return random_version;
}
struct _GRand
{
guint32 mt[N]; /* the array for the state vector */
guint mti;
};
/**
* g_rand_new_with_seed:
* @seed: a value to initialize the random number generator
*
* Creates a new random number generator initialized with @seed.
*
* Returns: the new #GRand
**/
GRand*
g_rand_new_with_seed (guint32 seed)
{
GRand *rand = g_new0 (GRand, 1);
g_rand_set_seed (rand, seed);
return rand;
}
/**
* g_rand_new_with_seed_array:
* @seed: an array of seeds to initialize the random number generator
* @seed_length: an array of seeds to initialize the random number
* generator
*
* Creates a new random number generator initialized with @seed.
*
* Returns: the new #GRand
*
* Since: 2.4
*/
GRand*
g_rand_new_with_seed_array (const guint32 *seed,
guint seed_length)
{
GRand *rand = g_new0 (GRand, 1);
g_rand_set_seed_array (rand, seed, seed_length);
return rand;
}
/**
* g_rand_new:
*
* Creates a new random number generator initialized with a seed taken
* either from `/dev/urandom` (if existing) or from the current time
* (as a fallback).
*
* On Windows, the seed is taken from rand_s().
*
* Returns: the new #GRand
*/
GRand*
g_rand_new (void)
{
guint32 seed[4];
#ifdef G_OS_UNIX
static gboolean dev_urandom_exists = TRUE;
if (dev_urandom_exists)
{
FILE* dev_urandom;
do
{
dev_urandom = fopen("/dev/urandom", "rb");
}
while G_UNLIKELY (dev_urandom == NULL && errno == EINTR);
if (dev_urandom)
{
int r;
setvbuf (dev_urandom, NULL, _IONBF, 0);
do
{
errno = 0;
r = fread (seed, sizeof (seed), 1, dev_urandom);
}
while G_UNLIKELY (errno == EINTR);
if (r != 1)
dev_urandom_exists = FALSE;
fclose (dev_urandom);
}
else
dev_urandom_exists = FALSE;
}
if (!dev_urandom_exists)
{
gint64 now_us = g_get_real_time ();
seed[0] = now_us / G_USEC_PER_SEC;
seed[1] = now_us % G_USEC_PER_SEC;
seed[2] = getpid ();
seed[3] = getppid ();
}
#else /* G_OS_WIN32 */
/* rand_s() is only available since Visual Studio 2005 and
* MinGW-w64 has a wrapper that will emulate rand_s() if it's not in msvcrt
*/
#if (defined(_MSC_VER) && _MSC_VER >= 1400) || defined(__MINGW64_VERSION_MAJOR)
gsize i;
for (i = 0; i < G_N_ELEMENTS (seed); i++)
rand_s (&seed[i]);
#else
#warning Using insecure seed for random number generation because of missing rand_s() in Windows XP
GTimeVal now;
g_get_current_time (&now);
seed[0] = now.tv_sec;
seed[1] = now.tv_usec;
seed[2] = getpid ();
seed[3] = 0;
#endif
#endif
return g_rand_new_with_seed_array (seed, 4);
}
/**
* g_rand_free:
* @rand_: a #GRand
*
* Frees the memory allocated for the #GRand.
*/
void
g_rand_free (GRand *rand)
{
g_return_if_fail (rand != NULL);
g_free (rand);
}
/**
* g_rand_copy:
* @rand_: a #GRand
*
* Copies a #GRand into a new one with the same exact state as before.
* This way you can take a snapshot of the random number generator for
* replaying later.
*
* Returns: the new #GRand
*
* Since: 2.4
*/
GRand*
g_rand_copy (GRand *rand)
{
GRand* new_rand;
g_return_val_if_fail (rand != NULL, NULL);
new_rand = g_new0 (GRand, 1);
memcpy (new_rand, rand, sizeof (GRand));
return new_rand;
}
/**
* g_rand_set_seed:
* @rand_: a #GRand
* @seed: a value to reinitialize the random number generator
*
* Sets the seed for the random number generator #GRand to @seed.
*/
void
g_rand_set_seed (GRand *rand,
guint32 seed)
{
g_return_if_fail (rand != NULL);
switch (get_random_version ())
{
case 20:
/* setting initial seeds to mt[N] using */
/* the generator Line 25 of Table 1 in */
/* [KNUTH 1981, The Art of Computer Programming */
/* Vol. 2 (2nd Ed.), pp102] */
if (seed == 0) /* This would make the PRNG produce only zeros */
seed = 0x6b842128; /* Just set it to another number */
rand->mt[0]= seed;
for (rand->mti=1; rand->mti<N; rand->mti++)
rand->mt[rand->mti] = (69069 * rand->mt[rand->mti-1]);
break;
case 22:
/* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
/* In the previous version (see above), MSBs of the */
/* seed affect only MSBs of the array mt[]. */
rand->mt[0]= seed;
for (rand->mti=1; rand->mti<N; rand->mti++)
rand->mt[rand->mti] = 1812433253UL *
(rand->mt[rand->mti-1] ^ (rand->mt[rand->mti-1] >> 30)) + rand->mti;
break;
default:
g_assert_not_reached ();
}
}
/**
* g_rand_set_seed_array:
* @rand_: a #GRand
* @seed: array to initialize with
* @seed_length: length of array
*
* Initializes the random number generator by an array of longs.
* Array can be of arbitrary size, though only the first 624 values
* are taken. This function is useful if you have many low entropy
* seeds, or if you require more then 32 bits of actual entropy for
* your application.
*
* Since: 2.4
*/
void
g_rand_set_seed_array (GRand *rand,
const guint32 *seed,
guint seed_length)
{
guint i, j, k;
g_return_if_fail (rand != NULL);
g_return_if_fail (seed_length >= 1);
g_rand_set_seed (rand, 19650218UL);
i=1; j=0;
k = (N>seed_length ? N : seed_length);
for (; k; k--)
{
rand->mt[i] = (rand->mt[i] ^
((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1664525UL))
+ seed[j] + j; /* non linear */
rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
i++; j++;
if (i>=N)
{
rand->mt[0] = rand->mt[N-1];
i=1;
}
if (j>=seed_length)
j=0;
}
for (k=N-1; k; k--)
{
rand->mt[i] = (rand->mt[i] ^
((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1566083941UL))
- i; /* non linear */
rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
i++;
if (i>=N)
{
rand->mt[0] = rand->mt[N-1];
i=1;
}
}
rand->mt[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */
}
/**
* g_rand_boolean:
* @rand_: a #GRand
*
* Returns a random #gboolean from @rand_.
* This corresponds to an unbiased coin toss.
*
* Returns: a random #gboolean
*/
/**
* g_rand_int:
* @rand_: a #GRand
*
* Returns the next random #guint32 from @rand_ equally distributed over
* the range [0..2^32-1].
*
* Returns: a random number
*/
guint32
g_rand_int (GRand *rand)
{
guint32 y;
static const guint32 mag01[2]={0x0, MATRIX_A};
/* mag01[x] = x * MATRIX_A for x=0,1 */
g_return_val_if_fail (rand != NULL, 0);
if (rand->mti >= N) { /* generate N words at one time */
int kk;
for (kk = 0; kk < N - M; kk++) {
y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
rand->mt[kk] = rand->mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1];
}
for (; kk < N - 1; kk++) {
y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
rand->mt[kk] = rand->mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1];
}
y = (rand->mt[N-1]&UPPER_MASK)|(rand->mt[0]&LOWER_MASK);
rand->mt[N-1] = rand->mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];
rand->mti = 0;
}
y = rand->mt[rand->mti++];
y ^= TEMPERING_SHIFT_U(y);
y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
y ^= TEMPERING_SHIFT_L(y);
return y;
}
/* transform [0..2^32] -> [0..1] */
#define G_RAND_DOUBLE_TRANSFORM 2.3283064365386962890625e-10
/**
* g_rand_int_range:
* @rand_: a #GRand
* @begin: lower closed bound of the interval
* @end: upper open bound of the interval
*
* Returns the next random #gint32 from @rand_ equally distributed over
* the range [@begin..@end-1].
*
* Returns: a random number
*/
gint32
g_rand_int_range (GRand *rand,
gint32 begin,
gint32 end)
{
guint32 dist = end - begin;
guint32 random = 0;
g_return_val_if_fail (rand != NULL, begin);
g_return_val_if_fail (end > begin, begin);
switch (get_random_version ())
{
case 20:
if (dist <= 0x10000L) /* 2^16 */
{
/* This method, which only calls g_rand_int once is only good
* for (end - begin) <= 2^16, because we only have 32 bits set
* from the one call to g_rand_int ().
*
* We are using (trans + trans * trans), because g_rand_int only
* covers [0..2^32-1] and thus g_rand_int * trans only covers
* [0..1-2^-32], but the biggest double < 1 is 1-2^-52.
*/
gdouble double_rand = g_rand_int (rand) *
(G_RAND_DOUBLE_TRANSFORM +
G_RAND_DOUBLE_TRANSFORM * G_RAND_DOUBLE_TRANSFORM);
random = (gint32) (double_rand * dist);
}
else
{
/* Now we use g_rand_double_range (), which will set 52 bits
* for us, so that it is safe to round and still get a decent
* distribution
*/
random = (gint32) g_rand_double_range (rand, 0, dist);
}
break;
case 22:
if (dist == 0)
random = 0;
else
{
/* maxvalue is set to the predecessor of the greatest
* multiple of dist less or equal 2^32.
*/
guint32 maxvalue;
if (dist <= 0x80000000u) /* 2^31 */
{
/* maxvalue = 2^32 - 1 - (2^32 % dist) */
guint32 leftover = (0x80000000u % dist) * 2;
if (leftover >= dist) leftover -= dist;
maxvalue = 0xffffffffu - leftover;
}
else
maxvalue = dist - 1;
do
random = g_rand_int (rand);
while (random > maxvalue);
random %= dist;
}
break;
default:
g_assert_not_reached ();
}
return begin + random;
}
/**
* g_rand_double:
* @rand_: a #GRand
*
* Returns the next random #gdouble from @rand_ equally distributed over
* the range [0..1).
*
* Returns: a random number
*/
gdouble
g_rand_double (GRand *rand)
{
/* We set all 52 bits after the point for this, not only the first
32. That's why we need two calls to g_rand_int */
gdouble retval = g_rand_int (rand) * G_RAND_DOUBLE_TRANSFORM;
retval = (retval + g_rand_int (rand)) * G_RAND_DOUBLE_TRANSFORM;
/* The following might happen due to very bad rounding luck, but
* actually this should be more than rare, we just try again then */
if (retval >= 1.0)
return g_rand_double (rand);
return retval;
}
/**
* g_rand_double_range:
* @rand_: a #GRand
* @begin: lower closed bound of the interval
* @end: upper open bound of the interval
*
* Returns the next random #gdouble from @rand_ equally distributed over
* the range [@begin..@end).
*
* Returns: a random number
*/
gdouble
g_rand_double_range (GRand *rand,
gdouble begin,
gdouble end)
{
gdouble r;
r = g_rand_double (rand);
return r * end - (r - 1) * begin;
}
static GRand *
get_global_random (void)
{
static GRand *global_random;
/* called while locked */
if (!global_random)
global_random = g_rand_new ();
return global_random;
}
/**
* g_random_boolean:
*
* Returns a random #gboolean.
* This corresponds to an unbiased coin toss.
*
* Returns: a random #gboolean
*/
/**
* g_random_int:
*
* Return a random #guint32 equally distributed over the range
* [0..2^32-1].
*
* Returns: a random number
*/
guint32
g_random_int (void)
{
guint32 result;
G_LOCK (global_random);
result = g_rand_int (get_global_random ());
G_UNLOCK (global_random);
return result;
}
/**
* g_random_int_range:
* @begin: lower closed bound of the interval
* @end: upper open bound of the interval
*
* Returns a random #gint32 equally distributed over the range
* [@begin..@end-1].
*
* Returns: a random number
*/
gint32
g_random_int_range (gint32 begin,
gint32 end)
{
gint32 result;
G_LOCK (global_random);
result = g_rand_int_range (get_global_random (), begin, end);
G_UNLOCK (global_random);
return result;
}
/**
* g_random_double:
*
* Returns a random #gdouble equally distributed over the range [0..1).
*
* Returns: a random number
*/
gdouble
g_random_double (void)
{
double result;
G_LOCK (global_random);
result = g_rand_double (get_global_random ());
G_UNLOCK (global_random);
return result;
}
/**
* g_random_double_range:
* @begin: lower closed bound of the interval
* @end: upper open bound of the interval
*
* Returns a random #gdouble equally distributed over the range
* [@begin..@end).
*
* Returns: a random number
*/
gdouble
g_random_double_range (gdouble begin,
gdouble end)
{
double result;
G_LOCK (global_random);
result = g_rand_double_range (get_global_random (), begin, end);
G_UNLOCK (global_random);
return result;
}
/**
* g_random_set_seed:
* @seed: a value to reinitialize the global random number generator
*
* Sets the seed for the global random number generator, which is used
* by the g_random_* functions, to @seed.
*/
void
g_random_set_seed (guint32 seed)
{
G_LOCK (global_random);
g_rand_set_seed (get_global_random (), seed);
G_UNLOCK (global_random);
}
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