rippled/include/xrpl/protocol/IOUAmount.h

#ifndef XRPL_BASICS_IOUAMOUNT_H_INCLUDED
#define XRPL_BASICS_IOUAMOUNT_H_INCLUDED

#include <xrpl/basics/LocalValue.h>
#include <xrpl/basics/Number.h>
#include <xrpl/beast/utility/Zero.h>

#include <boost/operators.hpp>

#include <cstdint>
#include <string>

namespace xrpl {

/** Floating point representation of amounts with high dynamic range

    Amounts are stored as a normalized signed mantissa and an exponent. The
    range of the normalized exponent is [-96,80] and the range of the absolute
    value of the normalized mantissa is [1000000000000000, 9999999999999999].

    Arithmetic operations can throw std::overflow_error during normalization
    if the amount exceeds the largest representable amount, but underflows
    will silently truncate to zero.
*/
class IOUAmount : private boost::totally_ordered<IOUAmount>,
                  private boost::additive<IOUAmount>
{
private:
    using mantissa_type = std::int64_t;
    using exponent_type = int;
    mantissa_type mantissa_;
    exponent_type exponent_;

    /** Adjusts the mantissa and exponent to the proper range.

        This can throw if the amount cannot be normalized, or is larger than
        the largest value that can be represented as an IOU amount. Amounts
        that are too small to be represented normalize to 0.
    */
    void
    normalize();

    static IOUAmount
    fromNumber(Number const& number);

public:
    IOUAmount() = default;
    explicit IOUAmount(Number const& other);
    IOUAmount(beast::Zero);
    IOUAmount(mantissa_type mantissa, exponent_type exponent);

    IOUAmount& operator=(beast::Zero);

    operator Number() const;

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

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

    IOUAmount
    operator-() const;

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

    bool
    operator<(IOUAmount const& other) const;

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

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

    exponent_type
    exponent() const noexcept;

    mantissa_type
    mantissa() const noexcept;

    static IOUAmount
    minPositiveAmount();

    friend std::ostream&
    operator<<(std::ostream& os, IOUAmount const& x)
    {
        return os << to_string(x);
    }
};

inline IOUAmount::IOUAmount(beast::Zero)
{
    *this = beast::zero;
}

inline IOUAmount::IOUAmount(mantissa_type mantissa, exponent_type exponent)
    : mantissa_(mantissa), exponent_(exponent)
{
    normalize();
}

inline IOUAmount&
IOUAmount::operator=(beast::Zero)
{
    // The -100 is used to allow 0 to sort less than small positive values
    // which will have a large negative exponent.
    mantissa_ = 0;
    exponent_ = -100;
    return *this;
}

inline IOUAmount::operator Number() const
{
    return Number{mantissa_, exponent_};
}

inline IOUAmount&
IOUAmount::operator-=(IOUAmount const& other)
{
    *this += -other;
    return *this;
}

inline IOUAmount
IOUAmount::operator-() const
{
    return {-mantissa_, exponent_};
}

inline bool
IOUAmount::operator==(IOUAmount const& other) const
{
    return exponent_ == other.exponent_ && mantissa_ == other.mantissa_;
}

inline bool
IOUAmount::operator<(IOUAmount const& other) const
{
    return Number{*this} < Number{other};
}

inline IOUAmount::operator bool() const noexcept
{
    return mantissa_ != 0;
}

inline int
IOUAmount::signum() const noexcept
{
    return (mantissa_ < 0) ? -1 : (mantissa_ ? 1 : 0);
}

inline IOUAmount::exponent_type
IOUAmount::exponent() const noexcept
{
    return exponent_;
}

inline IOUAmount::mantissa_type
IOUAmount::mantissa() const noexcept
{
    return mantissa_;
}

std::string
to_string(IOUAmount const& amount);

/* Return num*amt/den
   This function keeps more precision than computing
   num*amt, storing the result in an IOUAmount, then
   dividing by den.
*/
IOUAmount
mulRatio(
    IOUAmount const& amt,
    std::uint32_t num,
    std::uint32_t den,
    bool roundUp);

// Since many uses of the number class do not have access to a ledger,
// getSTNumberSwitchover needs to be globally accessible.

bool
getSTNumberSwitchover();

void
setSTNumberSwitchover(bool v);

/** RAII class to set and restore the Number switchover.
 */

class NumberSO
{
    bool saved_;

public:
    ~NumberSO()
    {
        setSTNumberSwitchover(saved_);
    }

    NumberSO(NumberSO const&) = delete;
    NumberSO&
    operator=(NumberSO const&) = delete;

    explicit NumberSO(bool v) : saved_(getSTNumberSwitchover())
    {
        setSTNumberSwitchover(v);
    }
};

}  // namespace xrpl

#endif