/src/solidity/libsolutil/FixedHash.h

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/*
  This file is part of solidity.

  solidity 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.

  solidity 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 solidity.  If not, see <http://www.gnu.org/licenses/>.
*/
// SPDX-License-Identifier: GPL-3.0
/** @file FixedHash.h
 * @author Gav Wood <i@gavwood.com>
 * @date 2014
 *
 * The FixedHash fixed-size "hash" container type.
 */

#pragma once

#include <libsolutil/CommonData.h>
#include <libsolutil/Numeric.h>

#include <boost/functional/hash.hpp>
#include <boost/io/ios_state.hpp>

#include <array>
#include <cstdint>
#include <algorithm>

namespace solidity::util
{

/// Fixed-size raw-byte array container type, with an API optimised for storing hashes.
/// Transparently converts to/from the corresponding arithmetic type; this will
/// assume the data contained in the hash is big-endian.
template <unsigned N>
class FixedHash
{
public:
  /// The corresponding arithmetic type.
  using Arith = boost::multiprecision::number<boost::multiprecision::cpp_int_backend<N * 8, N * 8, boost::multiprecision::unsigned_magnitude, boost::multiprecision::unchecked, void>>;

  /// The size of the container.
  enum { size = N };
  static_assert(N != 0);

  /// Method to convert from a string.
  enum ConstructFromStringType { FromHex, FromBinary };

  /// Method to convert from a string.
  enum ConstructFromHashType { AlignLeft, AlignRight, FailIfDifferent };

  /// Construct an empty hash.
  explicit FixedHash() { m_data.fill(0); }

  /// Construct from another hash, filling with zeroes or cropping as necessary.
  template <unsigned M> explicit FixedHash(FixedHash<M> const& _h, ConstructFromHashType _t)
  {
    m_data.fill(0);
    unsigned c = std::min(M, N);
    for (unsigned i = 0; i < c; ++i)
      m_data[_t == AlignRight ? N - 1 - i : i] = _h[_t == AlignRight ? M - 1 - i : i];
  }

  /// Convert from the corresponding arithmetic type.
  FixedHash(Arith const& _arith) { toBigEndian(_arith, m_data); }

  /// Explicitly construct, copying from a byte array.
  explicit FixedHash(bytes const& _array, ConstructFromHashType _sizeMismatchBehavior = FailIfDifferent)
  {
    if (_array.size() == N)
      memcpy(m_data.data(), _array.data(), _array.size());
    else
    {
      m_data.fill(0);
      if (_sizeMismatchBehavior != FailIfDifferent)
      {
        auto bytesToCopy = std::min<size_t>(_array.size(), N);
        for (size_t i = 0; i < bytesToCopy; ++i)
          if (_sizeMismatchBehavior == AlignRight)
            m_data[N - 1 - i] = _array[_array.size() - 1 - i];
          else
            m_data[i] = _array[i];
      }
    }
  }

  /// Explicitly construct, copying from a byte array.
  explicit FixedHash(bytesConstRef _b, ConstructFromHashType _t = FailIfDifferent)
  {
    if (_b.size() == N)
      memcpy(m_data.data(), _b.data(), std::min<size_t>(_b.size(), N));
    else
    {
      m_data.fill(0);
      if (_t != FailIfDifferent)
      {
        auto c = std::min<size_t>(_b.size(), N);
        for (size_t i = 0; i < c; ++i)
          if (_t == AlignRight)
            m_data[N - 1 - i] = _b[_b.size() - 1 - i];
          else
            m_data[i] = _b[i];
      }
    }
  }

  /// Explicitly construct, copying from a string.
  explicit FixedHash(std::string const& _s, ConstructFromStringType _t = FromHex, ConstructFromHashType _ht = FailIfDifferent):
    FixedHash(_t == FromHex ? fromHex(_s, WhenError::Throw) : solidity::util::asBytes(_s), _ht)
  {}

  /// Convert to arithmetic type.
  operator Arith() const { return fromBigEndian<Arith>(m_data); }

  // The obvious comparison operators.
  bool operator==(FixedHash const& _c) const { return m_data == _c.m_data; }
  bool operator!=(FixedHash const& _c) const { return m_data != _c.m_data; }
  /// Required to sort objects of this type or use them as map keys.
  bool operator<(FixedHash const& _c) const {
    for (unsigned i = 0; i < N; ++i)
    {
      if (m_data[i] < _c.m_data[i])
        return true;
      else if (m_data[i] > _c.m_data[i])
        return false;
    }
    return false;
  }

  /// @returns a particular byte from the hash.
  uint8_t& operator[](unsigned _i) { return m_data[_i]; }
  /// @returns a particular byte from the hash.
  uint8_t operator[](unsigned _i) const { return m_data[_i]; }

  /// @returns the hash as a user-readable hex string.
  std::string hex() const { return toHex(asBytes()); }

  /// @returns a mutable byte vector_ref to the object's data.
  bytesRef ref() { return bytesRef(m_data.data(), N); }

  /// @returns a constant byte vector_ref to the object's data.
  bytesConstRef ref() const { return bytesConstRef(m_data.data(), N); }

  /// @returns a mutable byte pointer to the object's data.
  uint8_t* data() { return m_data.data(); }

  /// @returns a constant byte pointer to the object's data.
  uint8_t const* data() const { return m_data.data(); }

  /// @returns a copy of the object's data as a byte vector.
  bytes asBytes() const { return bytes(data(), data() + N); }

private:
  std::array<uint8_t, N> m_data; ///< The binary data.
};

/// Stream I/O for the FixedHash class.
template <unsigned N>
inline std::ostream& operator<<(std::ostream& _out, FixedHash<N> const& _h)
{
  boost::io::ios_all_saver guard(_out);
  _out << std::noshowbase << std::hex << std::setfill('0');
  for (unsigned i = 0; i < N; ++i)
    _out << std::setw(2) << (int)_h[i];
  _out << std::dec;
  return _out;
}

// Common types of FixedHash.
using h256 = FixedHash<32>;
using h160 = FixedHash<20>;

}

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Created: 2025-06-24 07:59