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

99 lines
2.6 KiB
C
Raw Normal View History

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) 2008, 2009 William Hart
******************************************************************************/
#include <stdlib.h>
#include "fmpz_vec.h"
#include "fmpz_mod_poly.h"
void _fmpz_mod_poly_rem_basecase(fmpz *R,
const fmpz *A, slong lenA, const fmpz *B, slong lenB,
const fmpz_t invB, const fmpz_t p)
{
fmpz_t q;
slong iR;
fmpz_init(q);
if (R != A)
_fmpz_vec_set(R, A, lenA);
for (iR = lenA - 1; iR >= lenB - 1; iR--)
{
if (!fmpz_is_zero(R + iR))
{
fmpz_mul(q, R + iR, invB);
fmpz_mod(q, q, p);
_fmpz_vec_scalar_submul_fmpz(R + (iR - lenB + 1), B, lenB, q);
_fmpz_vec_scalar_mod_fmpz(R + (iR - lenB + 1), R + (iR - lenB + 1), lenB, p);
}
}
fmpz_clear(q);
}
void fmpz_mod_poly_rem_basecase(fmpz_mod_poly_t R,
const fmpz_mod_poly_t A, const fmpz_mod_poly_t B)
{
const slong lenA = A->length, lenB = B->length;
fmpz *r;
fmpz_t invB;
if (lenA < lenB)
{
fmpz_mod_poly_set(R, A);
return;
}
fmpz_init(invB);
fmpz_invmod(invB, B->coeffs + (lenB - 1), &(B->p));
if (R == B)
{
r = _fmpz_vec_init(lenA);
}
else
{
fmpz_mod_poly_fit_length(R, lenA);
r = R->coeffs;
}
_fmpz_mod_poly_rem_basecase(r, A->coeffs, lenA,
B->coeffs, lenB, invB, &(B->p));
if (R == B)
{
_fmpz_vec_clear(R->coeffs, R->alloc);
R->coeffs = r;
R->alloc = lenA;
R->length = lenA;
}
_fmpz_mod_poly_set_length(R, lenB - 1);
_fmpz_mod_poly_normalise(R);
fmpz_clear(invB);
}