FixedHash.h

/*
    This file is part of ethminer.

    ethminer 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.

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

#pragma once

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

#include "CommonData.h"

namespace dev
{
extern std::random_device s_fixedHashEngine;

/// 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:
#if defined(_WIN32)
    const char* k_ellipsis = "...";
#else
    const char* k_ellipsis = "\342\200\246";
#endif

    /// 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
    };

    /// A dummy flag to avoid accidental construction from pointer.
    enum ConstructFromPointerType
    {
        ConstructFromPointer
    };

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

    /// Construct an empty hash.
    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 = AlignLeft)
    {
        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); }

    /// Convert from unsigned
    explicit FixedHash(unsigned _u) { toBigEndian(_u, m_data); }

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

    /// Explicitly construct, copying from a bytes in memory with given pointer.
    explicit FixedHash(byte const* _bs, ConstructFromPointerType /*unused*/)
    {
        memcpy(m_data.data(), _bs, N);
    }

    /// Explicitly construct, copying from a  string.
    explicit FixedHash(std::string const& _s)
      : FixedHash(fromHex(_s, WhenError::Throw), FailIfDifferent)
    {}

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

    /// @returns true iff this is the empty hash.
    explicit operator bool() const
    {
        return std::any_of(m_data.begin(), m_data.end(), [](byte _b) { return _b != 0; });
    }

    // 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; }
    bool operator<(FixedHash const& _c) const
    {
        for (unsigned i = 0; i < N; ++i)
        {
            if (m_data[i] < _c.m_data[i])
                return true;
            if (m_data[i] > _c.m_data[i])
                return false;
        }
        return false;
    }
    bool operator>=(FixedHash const& _c) const { return !operator<(_c); }
    bool operator<=(FixedHash const& _c) const { return operator==(_c) || operator<(_c); }
    bool operator>(FixedHash const& _c) const { return !operator<=(_c); }

    // The obvious binary operators.
    FixedHash& operator^=(FixedHash const& _c)
    {
        for (unsigned i = 0; i < N; ++i)
            m_data[i] ^= _c.m_data[i];
        return *this;
    }
    FixedHash operator^(FixedHash const& _c) const { return FixedHash(*this) ^= _c; }
    FixedHash& operator|=(FixedHash const& _c)
    {
        for (unsigned i = 0; i < N; ++i)
            m_data[i] |= _c.m_data[i];
        return *this;
    }
    FixedHash operator|(FixedHash const& _c) const { return FixedHash(*this) |= _c; }
    FixedHash& operator&=(FixedHash const& _c)
    {
        for (unsigned i = 0; i < N; ++i)
            m_data[i] &= _c.m_data[i];
        return *this;
    }
    FixedHash operator&(FixedHash const& _c) const { return FixedHash(*this) &= _c; }
    FixedHash operator~() const
    {
        FixedHash ret;
        for (unsigned i = 0; i < N; ++i)
            ret[i] = ~m_data[i];
        return ret;
    }

    // Big-endian increment.
    FixedHash& operator++()
    {
        for (unsigned i = size; i > 0 && !++m_data[--i];)
        {
        }
        return *this;
    }

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

    /// @returns an abridged version of the hash as a user-readable hex string.

    std::string abridged() const { return toHex(ref().cropped(0, 4)) + k_ellipsis; }

    /// @returns the hash as a user-readable hex string.
    std::string hex(HexPrefix _prefix = HexPrefix::DontAdd) const { return toHex(ref(), 2, _prefix); }

    /// @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.
    byte* data() { return m_data.data(); }

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

    /// Populate with random data.
    template <class Engine>
    void randomize(Engine& _eng)
    {
        for (auto& i : m_data)
            i = (uint8_t)std::uniform_int_distribution<uint16_t>(0, 255)(_eng);
    }

    /// @returns a random valued object.
    static FixedHash random()
    {
        FixedHash ret;
        ret.randomize(s_fixedHashEngine);
        return ret;
    }

    struct hash
    {
        /// Make a hash of the object's data.
        size_t operator()(FixedHash const& _value) const
        {
            return boost::hash_range(_value.m_data.cbegin(), _value.m_data.cend());
        }
    };

    void clear() { m_data.fill(0); }

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

/// Fast equality operator for h256.
template <>
inline bool FixedHash<32>::operator==(FixedHash<32> const& _other) const
{
    const uint64_t* hash1 = (const uint64_t*)data();
    const uint64_t* hash2 = (const uint64_t*)_other.data();
    return (hash1[0] == hash2[0]) && (hash1[1] == hash2[1]) && (hash1[2] == hash2[2]) &&
           (hash1[3] == hash2[3]);
}

/// Fast std::hash compatible hash function object for h256.
template <>
inline size_t FixedHash<32>::hash::operator()(FixedHash<32> const& value) const
{
    uint64_t const* data = reinterpret_cast<uint64_t const*>(value.data());
    return boost::hash_range(data, data + 4);
}

/// Stream I/O for the FixedHash class.
template <unsigned N>
inline std::ostream& operator<<(std::ostream& _out, FixedHash<N> const& _h)
{
    _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 h2048 = FixedHash<256>;
using h1024 = FixedHash<128>;
using h520 = FixedHash<65>;
using h512 = FixedHash<64>;
using h256 = FixedHash<32>;
using h160 = FixedHash<20>;
using h128 = FixedHash<16>;
using h64 = FixedHash<8>;
using h512s = std::vector<h512>;
using h256s = std::vector<h256>;
using h160s = std::vector<h160>;

inline std::string toString(h256s const& _bs)
{
    std::ostringstream out;
    out << "[ ";
    for (auto i : _bs)
        out << i.abridged() << ", ";
    out << "]";
    return out.str();
}

}  // namespace dev

namespace std
{
/// Forward std::hash<dev::FixedHash> to dev::FixedHash::hash.
template <>
struct hash<dev::h64> : dev::h64::hash
{
};
template <>
struct hash<dev::h128> : dev::h128::hash
{
};
template <>
struct hash<dev::h160> : dev::h160::hash
{
};
template <>
struct hash<dev::h256> : dev::h256::hash
{
};
template <>
struct hash<dev::h512> : dev::h512::hash
{
};
}  // namespace std