rippled/include/xrpl/protocol/MPTAmount.h

//------------------------------------------------------------------------------
/*
    This file is part of rippled: https://github.com/ripple/rippled
    Copyright (c) 2024 Ripple Labs Inc.

    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.

    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================

#ifndef RIPPLE_PROTOCOL_MPTAMOUNT_H_INCLUDED
#define RIPPLE_PROTOCOL_MPTAMOUNT_H_INCLUDED

#include <xrpl/basics/Number.h>
#include <xrpl/basics/contract.h>
#include <xrpl/basics/safe_cast.h>
#include <xrpl/beast/utility/Zero.h>
#include <xrpl/json/json_value.h>

#include <boost/multiprecision/cpp_int.hpp>
#include <boost/operators.hpp>

#include <cstdint>
#include <optional>
#include <string>
#include <type_traits>

namespace ripple {

class MPTAmount : private boost::totally_ordered<MPTAmount>,
                  private boost::additive<MPTAmount>,
                  private boost::equality_comparable<MPTAmount, std::int64_t>,
                  private boost::additive<MPTAmount, std::int64_t>
{
public:
    using value_type = std::int64_t;

protected:
    value_type value_;

public:
    MPTAmount() = default;
    constexpr MPTAmount(MPTAmount const& other) = default;
    constexpr MPTAmount&
    operator=(MPTAmount const& other) = default;

    // Round to nearest, even on tie.
    explicit MPTAmount(Number const& x) : MPTAmount(static_cast<value_type>(x))
    {
    }

    constexpr explicit MPTAmount(value_type value);

    constexpr MPTAmount& operator=(beast::Zero);

    MPTAmount&
    operator+=(MPTAmount const& other);

    MPTAmount&
    operator-=(MPTAmount const& other);

    MPTAmount
    operator-() const;

    bool
    operator==(MPTAmount const& other) const;

    bool
    operator==(value_type other) const;

    bool
    operator<(MPTAmount const& other) const;

    /** Returns true if the amount is not zero */
    explicit constexpr
    operator bool() const noexcept;

    operator Number() const noexcept
    {
        return value();
    }

    /** Return the sign of the amount */
    constexpr int
    signum() const noexcept;

    /** Returns the underlying value. Code SHOULD NOT call this
        function unless the type has been abstracted away,
        e.g. in a templated function.
    */
    constexpr value_type
    value() const;

    static MPTAmount
    minPositiveAmount();
};

constexpr MPTAmount::MPTAmount(value_type value) : value_(value)
{
}

constexpr MPTAmount&
MPTAmount::operator=(beast::Zero)
{
    value_ = 0;
    return *this;
}

/** Returns true if the amount is not zero */
constexpr MPTAmount::operator bool() const noexcept
{
    return value_ != 0;
}

/** Return the sign of the amount */
constexpr int
MPTAmount::signum() const noexcept
{
    return (value_ < 0) ? -1 : (value_ ? 1 : 0);
}

/** Returns the underlying value. Code SHOULD NOT call this
    function unless the type has been abstracted away,
    e.g. in a templated function.
*/
constexpr MPTAmount::value_type
MPTAmount::value() const
{
    return value_;
}

inline std::string
to_string(MPTAmount const& amount)
{
    return std::to_string(amount.value());
}

inline MPTAmount
mulRatio(
    MPTAmount const& amt,
    std::uint32_t num,
    std::uint32_t den,
    bool roundUp)
{
    using namespace boost::multiprecision;
    using int128 = boost::multiprecision::int128_t;

    if (!den)
        Throw<std::runtime_error>("division by zero");

    int128 const amt128(amt.value());
    auto const neg = amt.value() < 0;
    auto const m = amt128 * num;
    auto r = m / den;
    if (m % den)
    {
        if (!neg && roundUp)
            r += 1;
        if (neg && !roundUp)
            r -= 1;
    }
    if (r > std::numeric_limits<MPTAmount::value_type>::max())
        Throw<std::overflow_error>("MPT mulRatio overflow");
    return MPTAmount(r.convert_to<MPTAmount::value_type>());
}

}  // namespace ripple

#endif  // RIPPLE_BASICS_MPTAMOUNT_H_INCLUDED