/* mpz_nextprime(p,t) - compute the next prime > t and store that in p.

Copyright (C) 1999, 2000 Free Software Foundation, Inc.

This file is part of the GNU MP Library.

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

The GNU MP 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 Library General Public
License for more details.

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

#include "gmp.h"
#include "gmp-impl.h"

void
#if __STDC__
mpz_nextprime (mpz_ptr p, mpz_srcptr t)
#else
mpz_nextprime (p, t)
     mpz_ptr    p;
     mpz_srcptr t;
#endif
{
  mpz_add_ui (p, t, 1L);
  while (! mpz_probab_prime_p (p, 5))
    mpz_add_ui (p, p, 1L);
}

#if 0
/* This code is not yet tested.  Will be enabled in 3.1. */

status unsigned short primes[] =
{
3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,
101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,
191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,
281,283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,
389,397,401,409,419,421,431,433,439,443,449,457,461,463,467,479,487,
491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,
607,613,617,619,631,641,643,647,653,659,661,673,677,683,691,701,709,
719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,
829,839,853,857,859,863,877,881,883,887,907,911,919,929,937,941,947,
953,967,971,977,983,991,997
};

#define NUMBER_OF_PRIMES 167

void
#if __STDC__
mpz_nextprime (mpz_ptr p, mpz_srcptr n)
#else
mpz_nextprime (p, n)
     mpz_ptr p;
     mpz_srcptr n;
#endif
{
  mpz_t tmp;
  unsigned short *moduli;
  unsigned long difference;
  int i;
  int composite;

  /* First handle tiny numbers */
  if (mpz_cmp_ui (n, 2) < 0)
    {
      mpz_set_ui (p, 2);
      return;
    }
  mpz_add_ui (p, n, 1);
  mpz_setbit (p, 0);

  if (mpz_cmp_ui (p, 7) <= 0)
    return;

  prime_limit = NUMBER_OF_PRIMES - 1;
  if (mpz_cmp_ui (p, primes[prime_limit]) <= 0)
    /* Just use first three entries (3,5,7) of table for small numbers */
    prime_limit = 3;
  if (prime_limit)
    {
      /* Compute residues modulo small odd primes */
      moduli = (unsigned short *) TMP_ALLOC (prime_limit * sizeof moduli[0]);
      for (i = 0; i < prime_limit; i++)
	moduli[i] = mpz_fdiv_ui (p, primes[i]);
    }
  for (difference = 0; ; difference += 2)
    {
      composite = 0;

      /* First check residues */
      for (i = 0; i < prime_limit; i++)
	{
	  int acc, pr;
	  composite |= (moduli[i] == 0);
	  acc = moduli[i] + 2;
	  pr = primes[i];
	  moduli[i] = acc >= pr ? acc - pr : acc;
	}
      if (composite)
	continue;

      mpz_add_ui (p, p, difference);
      difference = 0;

      /* Miller-Rabin test */
      if (mpz_millerrabin (p, 2))
	break;
    }
}
#endif