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/*
Copyright (C) 2009, 2011 William Hart
This file is part of FLINT.
FLINT is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 3 of the License, or
(at your option) any later version. See <https://www.gnu.org/licenses/>.
*/
#include "fft.h"
void mpn_normmod_2expp1(mp_limb_t * t, mp_size_t limbs)
{
mp_limb_signed_t hi = t[limbs];
if (hi)
{
t[limbs] = 0;
mpn_addmod_2expp1_1(t, limbs, -hi);
/* hi will now be in [-1,1] */
if ((hi = t[limbs]))
{
t[limbs] = 0;
mpn_addmod_2expp1_1(t, limbs, -hi);
if (t[limbs] == ~UWORD(0)) /* if we now have -1 (very unlikely) */
{
t[limbs] = 0;
mpn_addmod_2expp1_1(t, limbs, 1);
}
}
}
}