/*
   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

*/

class Squares {
std::vector<unsigned char> square_table;
const unsigned long M;
unsigned long max_skip;
public:
Squares(unsigned long M);
unsigned char const *valid_squares() { return square_table.data(); }
};

typedef uint16_t Skint; // skip integer type used in filter table, probably should be a member of Filter

class Filter {
std::vector<Skint> skip;
const unsigned skip_n;
const unsigned long M;
unsigned long smallest_candidate;
unsigned long max_skip;
public:
Filter(unsigned long M, unsigned skip_n, unsigned long NmodM, const unsigned char* const valid_squares);
inline unsigned get_skip(unsigned entry) { return skip[entry]; }
unsigned long get_offset_to_next(unsigned& skindex, unsigned long guess_modM);
Skint* get_table() { return skip.data(); }
unsigned long get_max_skip () { return max_skip;}
};

unsigned calc_tr(unsigned long M, unsigned long NmodM, const unsigned char* const valid_squares);