text: // Copyright (c) 2017, SUMOKOIN
  // Copyright (c) 2014-2016, The Monero Project
  //
  // Portions of this file are available under BSD-3 license. Please see ORIGINAL-LICENSE for details
  // All rights reserved.
  //
  // Ryo changes to this code are in public domain. Please note, other licences may apply to the file.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
  // EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  // MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
  // THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  // PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  // STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
  // THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  //
  // Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers
  
  #pragma once
  
  #include <cstdint>
  #include <vector>
  
  #include "crypto/hash.h"
  
  namespace cryptonote
  {
  typedef std::uint64_t difficulty_type;
  
  /**
     * @brief checks if a hash fits the given difficulty
     *
     * The hash passes if (hash * difficulty) < 2^192.
     * Phrased differently, if (hash * difficulty) fits without overflow into
     * the least significant 192 bits of the 256 bit multiplication result.
     *
     * @param hash the hash to check
     * @param difficulty the difficulty to check against
     *
     * @return true if valid, else false
     */
  bool check_hash(const crypto::hash &hash, difficulty_type difficulty);
  difficulty_type next_difficulty_v1(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds);
  difficulty_type next_difficulty_v2(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds);
  difficulty_type next_difficulty_v3(const std::vector<std::uint64_t> &timestamps, const std::vector<difficulty_type> &cumulative_difficulties);
  difficulty_type next_difficulty_v4(std::vector<uint64_t> timestamps, const std::vector<difficulty_type>& cumulative_difficulties);
  template<size_t N>
  void interpolate_timestamps(std::vector<uint64_t>& timestamps);
  }
  