pqc/external/flint-2.4.3/fmpz_poly/divides.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 William Hart
******************************************************************************/
#include <gmp.h>
#include <stdlib.h>
#include "flint.h"
#include "fmpz.h"
#include "fmpz_poly.h"
int _fmpz_poly_divides(fmpz * q, const fmpz * a,
slong len1, const fmpz * b, slong len2)
{
fmpz * r = _fmpz_vec_init(len1);
_fmpz_poly_divrem(q, r, a, len1, b, len2);
FMPZ_VEC_NORM(r, len1);
_fmpz_vec_clear(r, len1);
return (len1 == 0);
}
int fmpz_poly_divides(fmpz_poly_t q, const fmpz_poly_t a, const fmpz_poly_t b)
{
if (fmpz_poly_is_zero(b))
{
flint_printf("Exception (fmpz_poly_divides). Division by zero.\n");
abort();
}
if (fmpz_poly_is_zero(a))
{
fmpz_poly_zero(q);
return 1;
}
if (a->length < b->length)
{
return 0;
}
{
const slong lenQ = a->length - b->length + 1;
int res;
if (q == a || q == b)
{
fmpz_poly_t t;
fmpz_poly_init2(t, lenQ);
res = _fmpz_poly_divides(t->coeffs, a->coeffs, a->length, b->coeffs, b->length);
_fmpz_poly_set_length(t, lenQ);
_fmpz_poly_normalise(t);
fmpz_poly_swap(q, t);
fmpz_poly_clear(t);
}
else
{
fmpz_poly_fit_length(q, lenQ);
res = _fmpz_poly_divides(q->coeffs, a->coeffs, a->length, b->coeffs, b->length);
_fmpz_poly_set_length(q, lenQ);
_fmpz_poly_normalise(q);
}
return res;
}
}