pqc/external/flint-2.4.3/ulong_extras/randprime.c
2014-05-24 23:16:06 +02:00

74 lines
2.1 KiB
C

/*=============================================================================
This file is part of FLINT.
FLINT 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 of the License, or
(at your option) any later version.
FLINT 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 FLINT; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2007, 2008 William Hart
Copyright (C) 2008 Peter Shrimpton
Copyright (C) 2011 Fredrik Johansson
******************************************************************************/
#define ulong ulongxx /* interferes with system includes */
#include <stdlib.h>
#include <stdio.h>
#undef ulong
#define ulong mp_limb_t
#include "flint.h"
#include "ulong_extras.h"
mp_limb_t n_randprime(flint_rand_t state, ulong bits, int proved)
{
mp_limb_t rand;
if (bits < 2)
{
flint_printf("Exception in n_randprime: attempt to generate prime < 2!\n");
abort();
}
if (bits == FLINT_BITS)
{
do { rand = n_randbits(state, bits); }
while (rand >= UWORD_MAX_PRIME);
rand = n_nextprime(rand, proved);
}
else if (bits == 2)
{
rand = 2 + n_randint(state, 2);
}
else
{
do
{
rand = n_randbits(state, bits);
rand = n_nextprime(rand, proved);
} while ((rand >> bits) > WORD(0));
}
return rand;
}
mp_limb_t n_randtest_prime(flint_rand_t state, int proved)
{
return n_randprime(state, 2 + n_randint(state, FLINT_BITS - 1), proved);
}