text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2015 The Bitcoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #ifndef NAJAFBIT_UINT256_H
  #define NAJAFBIT_UINT256_H
  
  #include <assert.h>
  #include <cstring>
  #include <stdexcept>
  #include <stdint.h>
  #include <string>
  #include <vector>
  #include "crypto/common.h"
  
  /** Template base class for fixed-sized opaque blobs. */
  template<unsigned int BITS>
  class base_blob
  {
  protected:
      enum { WIDTH=BITS/8 };
      uint8_t data[WIDTH];
  public:
      base_blob()
      {
          memset(data, 0, sizeof(data));
      }
  
      explicit base_blob(const std::vector<unsigned char>& vch);
  
      bool IsNull() const
      {
          for (int i = 0; i < WIDTH; i++)
              if (data[i] != 0)
                  return false;
          return true;
      }
  
      void SetNull()
      {
          memset(data, 0, sizeof(data));
      }
  
      friend inline bool operator==(const base_blob& a, const base_blob& b) { return memcmp(a.data, b.data, sizeof(a.data)) == 0; }
      friend inline bool operator!=(const base_blob& a, const base_blob& b) { return memcmp(a.data, b.data, sizeof(a.data)) != 0; }
      friend inline bool operator<(const base_blob& a, const base_blob& b) { return memcmp(a.data, b.data, sizeof(a.data)) < 0; }
  
      std::string GetHex() const;
      void SetHex(const char* psz);
      void SetHex(const std::string& str);
      std::string ToString() const;
  
      unsigned char* begin()
      {
          return &data[0];
      }
  
      unsigned char* end()
      {
          return &data[WIDTH];
      }
  
      const unsigned char* begin() const
      {
          return &data[0];
      }
  
      const unsigned char* end() const
      {
          return &data[WIDTH];
      }
  
      unsigned int size() const
      {
          return sizeof(data);
      }
  
      unsigned int GetSerializeSize(int nType, int nVersion) const
      {
          return sizeof(data);
      }
  
      template<typename Stream>
      void Serialize(Stream& s, int nType, int nVersion) const
      {
          s.write((char*)data, sizeof(data));
      }
  
      template<typename Stream>
      void Unserialize(Stream& s, int nType, int nVersion)
      {
          s.read((char*)data, sizeof(data));
      }
  };
  
  /** 160-bit opaque blob.
   * @note This type is called uint160 for historical reasons only. It is an opaque
   * blob of 160 bits and has no integer operations.
   */
  class uint160 : public base_blob<160> {
  public:
      uint160() {}
      uint160(const base_blob<160>& b) : base_blob<160>(b) {}
      explicit uint160(const std::vector<unsigned char>& vch) : base_blob<160>(vch) {}
  };
  
  /** 256-bit opaque blob.
   * @note This type is called uint256 for historical reasons only. It is an
   * opaque blob of 256 bits and has no integer operations. Use arith_uint256 if
   * those are required.
   */
  class uint256 : public base_blob<256> {
  public:
      uint256() {}
      uint256(const base_blob<256>& b) : base_blob<256>(b) {}
      explicit uint256(const std::vector<unsigned char>& vch) : base_blob<256>(vch) {}
  
      /** A cheap hash function that just returns 64 bits from the result, it can be
       * used when the contents are considered uniformly random. It is not appropriate
       * when the value can easily be influenced from outside as e.g. a network adversary could
       * provide values to trigger worst-case behavior.
       */
      uint64_t GetCheapHash() const
      {
          return ReadLE64(data);
      }
  
      /** A more secure, salted hash function.
       * @note This hash is not stable between little and big endian.
       */
      uint64_t GetHash(const uint256& salt) const;
  };
  
  /* uint256 from const char *.
   * This is a separate function because the constructor uint256(const char*) can result
   * in dangerously catching uint256(0).
   */
  inline uint256 uint256S(const char *str)
  {
      uint256 rv;
      rv.SetHex(str);
      return rv;
  }
  /* uint256 from std::string.
   * This is a separate function because the constructor uint256(const std::string &str) can result
   * in dangerously catching uint256(0) via std::string(const char*).
   */
  inline uint256 uint256S(const std::string& str)
  {
      uint256 rv;
      rv.SetHex(str);
      return rv;
  }
  
  #endif // NAJAFBIT_UINT256_H
  