derive.hpp

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//This file is part of Bertini 2.
//
//derive.hpp 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 3 of the License, or
//(at your option) any later version.
//
//derive.hpp 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 derive.hpp.  If not, see <http://www.gnu.org/licenses/>.
//
// Copyright(C) Bertini2 Development Team
//
// See <http://www.gnu.org/licenses/> for a copy of the license,
// as well as COPYING.  Bertini2 is provided with permitted
// additional terms in the b2/licenses/ directory.

 
#pragma once
 
#include <cstdint>
 
#include "bertini2/detail/sha256.hpp"
#include "bertini2/mpfr_extensions.hpp"   // mpz_int / real_mp (NOT num_traits: that would cycle through random.hpp)
#include "bertini2/records/draw_functions.hpp"
 
namespace bertini {
namespace records {

constexpr char RandomDerivationVersion[] = "b2rand/1";

class DrawStream
{
public:
    DrawStream() = default;

    void Reseed(std::uint64_t master, std::uint64_t domain, std::uint64_t index);

    std::uint64_t Uint64();

    double UnitDouble();

    double SymmetricDouble();

    mpz_int Bits(unsigned num_bits);

    mpz_int IntSymmetric(mpz_int const& bound);

    real_mp UnitRealMp(unsigned digits);
 
private:
    // Refill block_ with SHA-256(key || counter) and advance the counter.
    void NextBlock();
    // The next unconsumed stream byte (self-seeding from entropy if never seeded).
    unsigned char NextByte();
 
    detail::Digest256 key_;      
    std::uint64_t counter_ = 0;  
    unsigned char block_[32];    
    unsigned offset_ = 32;       
    bool seeded_ = false;        
};

DrawStream& ThreadDrawStream();
 
} // namespace records
} // namespace bertini