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

90 lines
2.6 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) 2009 William Hart
Copyright (C) 2010 Sebastian Pancratz
******************************************************************************/
#include <limits.h>
#include <gmp.h>
#include "flint.h"
#include "fmpz.h"
#include "ulong_extras.h"
mp_limb_t n_randtest_bits(flint_rand_t state, int bits)
{
mp_limb_t m;
mp_limb_t n;
m = n_randlimb(state);
if (m & UWORD(7))
{
n = n_randbits(state, bits);
}
else
{
m >>= 3;
switch (m & UWORD(7))
{
case 0: n = 0; break;
case 1: n = 1; break;
case 2: n = COEFF_MAX; break;
case 3: n = WORD_MAX; break;
case 4: n = UWORD_MAX; break;
case 5: n = (UWORD(1)<<n_randint(state, FLINT_BITS))
- (UWORD(1)<<n_randint(state, FLINT_BITS));
break;
case 6: n = (UWORD(1)<<n_randint(state, FLINT_BITS));
break;
case 7: n = -(UWORD(1)<<n_randint(state, FLINT_BITS));
break;
default: n = 0;
}
if (bits < FLINT_BITS)
n &= ((UWORD(1)<<bits) - UWORD(1)); /* mask it off */
if (bits) /* set most significant bit */
n |= (UWORD(1)<<(bits - 1));
else
n = 0;
}
return n;
}
mp_limb_t n_randtest(flint_rand_t state)
{
return n_randtest_bits(state, n_randint(state, FLINT_BITS + 1));
}
mp_limb_t n_randtest_not_zero(flint_rand_t state)
{
mp_limb_t n;
while ((n = n_randtest(state)) == 0) ;
return n;
}