arith_uint256.h

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-present 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 BITCOIN_ARITH_UINT256_H
#define BITCOIN_ARITH_UINT256_H

#include <compare>
#include <cstdint>
#include <cstring>
#include <limits>
#include <stdexcept>
#include <string>

class uint256;

class uint_error : public std::runtime_error {
public:
    explicit uint_error(const std::string& str) : std::runtime_error(str) {}
};

template <unsigned int BITS>
class base_uint
{
protected:
    static_assert(BITS / 32 > 0 && BITS % 32 == 0, "Template parameter BITS must be a positive multiple of 32.");
    static constexpr int WIDTH = BITS / 32;
    uint32_t pn[WIDTH];

public:
    constexpr base_uint()
    {
        for (int i = 0; i < WIDTH; i++)
            pn[i] = 0;
    }

    base_uint(const base_uint& b) = default;
    base_uint& operator=(const base_uint& b) = default;

    constexpr base_uint(uint64_t b)
    {
        pn[0] = (unsigned int)b;
        pn[1] = (unsigned int)(b >> 32);
        for (int i = 2; i < WIDTH; i++)
            pn[i] = 0;
    }

    base_uint operator~() const
    {
        base_uint ret;
        for (int i = 0; i < WIDTH; i++)
            ret.pn[i] = ~pn[i];
        return ret;
    }

    base_uint operator-() const
    {
        base_uint ret;
        for (int i = 0; i < WIDTH; i++)
            ret.pn[i] = ~pn[i];
        ++ret;
        return ret;
    }

    double getdouble() const;

    base_uint& operator=(uint64_t b)
    {
        pn[0] = (unsigned int)b;
        pn[1] = (unsigned int)(b >> 32);
        for (int i = 2; i < WIDTH; i++)
            pn[i] = 0;
        return *this;
    }

    base_uint& operator^=(const base_uint& b)
    {
        for (int i = 0; i < WIDTH; i++)
            pn[i] ^= b.pn[i];
        return *this;
    }

    base_uint& operator&=(const base_uint& b)
    {
        for (int i = 0; i < WIDTH; i++)
            pn[i] &= b.pn[i];
        return *this;
    }

    base_uint& operator|=(const base_uint& b)
    {
        for (int i = 0; i < WIDTH; i++)
            pn[i] |= b.pn[i];
        return *this;
    }

    base_uint& operator^=(uint64_t b)
    {
        pn[0] ^= (unsigned int)b;
        pn[1] ^= (unsigned int)(b >> 32);
        return *this;
    }

    base_uint& operator|=(uint64_t b)
    {
        pn[0] |= (unsigned int)b;
        pn[1] |= (unsigned int)(b >> 32);
        return *this;
    }

    base_uint& operator<<=(unsigned int shift);
    base_uint& operator>>=(unsigned int shift);

    base_uint& operator+=(const base_uint& b)
    {
        uint64_t carry = 0;
        for (int i = 0; i < WIDTH; i++)
        {
            uint64_t n = carry + pn[i] + b.pn[i];
            pn[i] = n & 0xffffffff;
            carry = n >> 32;
        }
        return *this;
    }

    base_uint& operator-=(const base_uint& b)
    {
        *this += -b;
        return *this;
    }

    base_uint& operator+=(uint64_t b64)
    {
        base_uint b;
        b = b64;
        *this += b;
        return *this;
    }

    base_uint& operator-=(uint64_t b64)
    {
        base_uint b;
        b = b64;
        *this += -b;
        return *this;
    }

    base_uint& operator*=(uint32_t b32);
    base_uint& operator*=(const base_uint& b);
    base_uint& operator/=(const base_uint& b);

    base_uint& operator++()
    {
        // prefix operator
        int i = 0;
        while (i < WIDTH && ++pn[i] == 0)
            i++;
        return *this;
    }

    base_uint operator++(int)
    {
        // postfix operator
        const base_uint ret = *this;
        ++(*this);
        return ret;
    }

    base_uint& operator--()
    {
        // prefix operator
        int i = 0;
        while (i < WIDTH && --pn[i] == std::numeric_limits<uint32_t>::max())
            i++;
        return *this;
    }

    base_uint operator--(int)
    {
        // postfix operator
        const base_uint ret = *this;
        --(*this);
        return ret;
    }

    int CompareTo(const base_uint& b) const;
    bool EqualTo(uint64_t b) const;

    friend inline base_uint operator+(const base_uint& a, const base_uint& b) { return base_uint(a) += b; }
    friend inline base_uint operator-(const base_uint& a, const base_uint& b) { return base_uint(a) -= b; }
    friend inline base_uint operator*(const base_uint& a, const base_uint& b) { return base_uint(a) *= b; }
    friend inline base_uint operator/(const base_uint& a, const base_uint& b) { return base_uint(a) /= b; }
    friend inline base_uint operator|(const base_uint& a, const base_uint& b) { return base_uint(a) |= b; }
    friend inline base_uint operator&(const base_uint& a, const base_uint& b) { return base_uint(a) &= b; }
    friend inline base_uint operator^(const base_uint& a, const base_uint& b) { return base_uint(a) ^= b; }
    friend inline base_uint operator>>(const base_uint& a, int shift) { return base_uint(a) >>= shift; }
    friend inline base_uint operator<<(const base_uint& a, int shift) { return base_uint(a) <<= shift; }
    friend inline base_uint operator*(const base_uint& a, uint32_t b) { return base_uint(a) *= b; }
    friend inline bool operator==(const base_uint& a, const base_uint& b) { return memcmp(a.pn, b.pn, sizeof(a.pn)) == 0; }
    friend inline std::strong_ordering operator<=>(const base_uint& a, const base_uint& b) { return a.CompareTo(b) <=> 0; }
    friend inline bool operator==(const base_uint& a, uint64_t b) { return a.EqualTo(b); }

    std::string GetHex() const;
    std::string ToString() const;

    unsigned int size() const
    {
        return sizeof(pn);
    }

    unsigned int bits() const;

    uint64_t GetLow64() const
    {
        static_assert(WIDTH >= 2, "Assertion WIDTH >= 2 failed (WIDTH = BITS / 32). BITS is a template parameter.");
        return pn[0] | (uint64_t)pn[1] << 32;
    }
};

class arith_uint256 : public base_uint<256>
{
public:
    constexpr arith_uint256() = default;
    constexpr arith_uint256(const base_uint& b) : base_uint(b) {}
    constexpr arith_uint256(uint64_t b) : base_uint(b) {}

    arith_uint256& SetCompact(uint32_t nCompact, bool *pfNegative = nullptr, bool *pfOverflow = nullptr);
    uint32_t GetCompact(bool fNegative = false) const;

    friend uint256 ArithToUint256(const arith_uint256 &);
    friend arith_uint256 UintToArith256(const uint256 &);
};

// Keeping the trivially copyable property is beneficial for performance
static_assert(std::is_trivially_copyable_v<arith_uint256>);

uint256 ArithToUint256(const arith_uint256 &);
arith_uint256 UintToArith256(const uint256 &);

extern template class base_uint<256>;

#endif // BITCOIN_ARITH_UINT256_H