/*
     This file is part of GNUnet.
     (C) 2001, 2002, 2003, 2004 Christian Grothoff (and other contributing authors)

     GNUnet is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published
     by the Free Software Foundation; either version 2, or (at your
     option) any later version.

     GNUnet 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
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with GNUnet; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
     Boston, MA 02111-1307, USA.

*/

/**
 * @file util/random_gcrypt.c
 * @brief functions to gather random numbers
 * @author Christian Grothoff
 */ 
#include "platform.h"
#include "gnunet_util.h"
#include "locking_gcrypt.h"
#include <gcrypt.h>

/**
 * Initialize Random number generator.
 */
void initRAND() {
  gcry_control(GCRYCTL_DISABLE_SECMEM, 0);
  if (! gcry_check_version(GCRYPT_VERSION))
    errexit(_("libgcrypt has not the expected version (version %s is required).\n"),
	    GCRYPT_VERSION);
  srand((unsigned int)time(NULL));
  lockGcrypt();
#ifdef gcry_fast_random_poll
  gcry_fast_random_poll ();
#endif
  unlockGcrypt();
}

/**
 * @return a random value in the interval [0,i[. 
 */
unsigned int randomi(unsigned int i) {
  static unsigned int invokeCount;
  unsigned int ret;

  lockGcrypt();
  /* see http://lists.gnupg.org/pipermail/gcrypt-devel/2004-May/000613.html */
  if ( (invokeCount++ % 256) == 0) {
#ifdef gcry_fast_random_poll
    gcry_fast_random_poll ();
#endif
  }
  GNUNET_ASSERT(i > 0);
  ret = rand();
  gcry_randomize((unsigned char*)&ret,
		 sizeof(unsigned int),
		 GCRY_STRONG_RANDOM);
  unlockGcrypt();
  ret = ret % i;
  GNUNET_ASSERT((ret >= 0) && (ret < i));
  return ret;
}

/**
 * Get an array with a random permutation of the numbers 0...n-1.
 */
int * permute(int n) {
  int * ret;
  int i;
  int tmp;
  unsigned int x;    

  GNUNET_ASSERT(n>0);
  ret = (int*)MALLOC(n * sizeof(int));
  for (i=0;i<n;i++)
    ret[i] = i;
  for (i=0;i<n;i++) {
    x = randomi(n);
    tmp = ret[x];
    ret[x] = ret[i];
    ret[i] = tmp;
  }
  return ret;
}

/**
 * Random on unsigned 64-bit values.
 */
unsigned long long randomi64(unsigned long long u) {
  unsigned long long ret;

  lockGcrypt();
  gcry_randomize((unsigned char *) &ret,
		 sizeof(unsigned long long),
		 GCRY_STRONG_RANDOM);
  unlockGcrypt();
  return ret % u;
}