/* 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);

}