pqc/external/flint-2.4.3/fmpz_mod_poly/shift_right.c

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2014-05-18 22:03:37 +00:00
/*=============================================================================
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) 2011, 2010 Sebastian Pancratz
Copyright (C) 2009, 2008 William Hart
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "fmpz.h"
#include "fmpz_mod_poly.h"
void
_fmpz_mod_poly_shift_right(fmpz * res, const fmpz * poly, slong len, slong n)
{
slong i;
/* Copy in forward order to avoid writing over unshifted coefficients */
if (res != poly)
{
for (i = 0; i < len - n; i++)
fmpz_set(res + i, poly + n + i);
}
else
{
for (i = 0; i < len - n; i++)
fmpz_swap(res + i, res + n + i);
}
}
void
fmpz_mod_poly_shift_right(fmpz_mod_poly_t res, const fmpz_mod_poly_t poly, slong n)
{
if (n == 0)
{
fmpz_mod_poly_set(res, poly);
return;
}
if (poly->length <= n)
{
fmpz_mod_poly_zero(res);
return;
}
fmpz_mod_poly_fit_length(res, poly->length - n);
_fmpz_mod_poly_shift_right(res->coeffs, poly->coeffs, poly->length, n);
_fmpz_mod_poly_set_length(res, poly->length - n);
}