monero/src/cryptonote_core/checkpoints.h

// Copyright (c) 2014-2016, The Monero Project
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// Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers

#pragma once
#include <map>
#include <vector>
#include "cryptonote_basic_impl.h"


namespace cryptonote
{
  /**
   * @brief A container for blockchain checkpoints
   *
   * A checkpoint is a pre-defined hash for the block at a given height.
   * Some of these are compiled-in, while others can be loaded at runtime
   * either from a json file or via DNS from a checkpoint-hosting server.
   */
  class checkpoints
  {
  public:

    /**
     * @brief default constructor
     */
    checkpoints();

    /**
     * @brief adds a checkpoint to the container
     *
     * @param height the height of the block the checkpoint is for
     * @param hash_str the hash of the block, as a string
     *
     * @return false if parsing the hash fails, or if the height is a duplicate
     *         AND the existing checkpoint hash does not match the new one,
     *         otherwise returns true
     */
    bool add_checkpoint(uint64_t height, const std::string& hash_str);

    /**
     * @brief checks if there is a checkpoint in the future
     *
     * This function checks if the height passed is lower than the highest
     * checkpoint.
     *
     * @param height the height to check against
     *
     * @return false if no checkpoints, otherwise returns whether or not
     *         the height passed is lower than the highest checkpoint.
     */
    bool is_in_checkpoint_zone(uint64_t height) const;

    /**
     * @brief checks if the given height and hash agree with the checkpoints
     *
     * This function checks if the given height and hash exist in the
     * checkpoints container.  If so, it returns whether or not the passed
     * parameters match the stored values.
     *
     * @param height the height to be checked
     * @param h the hash to be checked
     * @param is_a_checkpoint return-by-reference if there is a checkpoint at the given height
     *
     * @return true if there is no checkpoint at the given height, 
     *         true if the passed parameters match the stored checkpoint, 
     *         false otherwise
     */
    bool check_block(uint64_t height, const crypto::hash& h, bool& is_a_checkpoint) const;

    /**
     * @overload
     */
    bool check_block(uint64_t height, const crypto::hash& h) const;

    /**
     * @brief checks if alternate chain blocks should be kept for a given height
     *
     * this basically says if the blockchain is smaller than the first
     * checkpoint then alternate blocks are allowed.  Alternatively, if the
     * last checkpoint *before* the end of the current chain is also before
     * the block to be added, then this is fine.
     *
     * @param blockchain_height the current blockchain height
     * @param block_height the height of the block to be added as alternate
     *
     * @return true if alternate blocks are allowed given the parameters, 
     *         otherwise false
     */
    bool is_alternative_block_allowed(uint64_t blockchain_height, uint64_t block_height) const;

    /**
     * @brief gets the highest checkpoint height
     *
     * @return the height of the highest checkpoint
     */
    uint64_t get_max_height() const;

    /**
     * @brief gets the checkpoints container
     *
     * @return a const reference to the checkpoints container
     */
    const std::map<uint64_t, crypto::hash>& get_points() const;

    /**
     * @brief checks if our checkpoints container conflicts with another
     *
     * A conflict refers to a case where both checkpoint sets have a checkpoint
     * for a specific height but their hashes for that height do not match.
     *
     * @param other the other checkpoints instance to check against
     *
     * @return false if any conflict is found, otherwise true
     */
    bool check_for_conflicts(const checkpoints& other) const;


  private:

    std::map<uint64_t, crypto::hash> m_points; //!< the checkpoints container

  };
}