/*
   Copyright (C) 2022 Stephen Hewitt, cambridgeclarion.org

   This file is part of a programme to research fast Fermat factorisation algorithms.

   This is free software: you can redistribute it and/or modify
   it under the terms of version 3 of the GNU General Public License as
   published by the Free Software Foundation.

   It 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 Licence
   along with this programme.  If not, see <https://www.gnu.org/licenses/>.

   A copy of the licence is also available at
   https://www.cambridgeclarion.org/download/GPLv3.txt
   It has the following cryptographic hash
   SHA256 3972dc9744f6499f0f9b2dbf76696f2ae7ad8af9b23dde66d6af86c9dfb36986

*/

#include <sys/time.h>
#include "gmp.h"
#include "zf.h"

/*
   @N is number factorised, presumed to be of form pq where p and q are large primes
   @candidate is small square s^2 where b^2 = s^2 + N
*/

int check_result(mpz_t candidate, mpz_t N)
{
    mpz_t pp;
    mpz_init(pp);
    mpz_t qq;
    mpz_init(qq);

    mpz_t check;
    mpz_init(check);

    mpz_t small;
    mpz_init(small);

    mpz_t big;
    mpz_init(big);

    mpz_sqrt(small, candidate);

    mpz_add(candidate, N, candidate);
    mpz_sqrt(big, candidate);

    mpz_add(pp, big, small);
    mpz_sub(qq, big, small);

    mpz_mul(check, pp, qq);
    if (mpz_cmp(check, N))
    {
        return 75; //  factorisation failed, supposed pq is not equal to N
    }
    return 0;
}

/* returns the time in seconds since time tv_begin until time tv_end, as a float */

double elapsed_secs(struct timeval tv_end, struct timeval tv_begin)
{
    // following as integer for precision because may be big numbers with a small difference
    time_t elapsed_integer = tv_end.tv_sec - tv_begin.tv_sec;

    return elapsed_integer + ((double)tv_end.tv_usec - tv_begin.tv_usec)/1000000;
}