mirror of
https://github.com/XRPLF/rippled.git
synced 2025-12-06 17:27:55 +00:00
540 lines
12 KiB
C++
540 lines
12 KiB
C++
#ifndef XRPL_BASICS_NUMBER_H_INCLUDED
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#define XRPL_BASICS_NUMBER_H_INCLUDED
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#ifdef _MSC_VER
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#include <boost/multiprecision/cpp_int.hpp>
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#endif
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#include <cstdint>
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#include <limits>
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#include <optional>
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#include <ostream>
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#include <string>
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namespace ripple {
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class Number;
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std::string
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to_string(Number const& amount);
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template <typename T>
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constexpr std::optional<int>
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logTen(T value)
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{
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int power = 0;
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while (value >= 10 && value % 10 == 0)
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{
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value /= 10;
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++power;
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}
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if (value == 1)
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return power;
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return std::nullopt;
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}
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template <typename T>
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constexpr bool
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isPowerOfTen(T value)
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{
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return logTen(value).has_value();
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}
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#ifdef _MSC_VER
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using numberuint128 = boost::multiprecision::uint128_t;
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using numberint128 = boost::multiprecision::int128_t;
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#else // !defined(_MSC_VER)
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using numberuint128 = __uint128_t;
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using numberint128 = __int128_t;
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#endif // !defined(_MSC_VER)
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struct MantissaRange
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{
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using rep = numberint128;
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explicit constexpr MantissaRange(rep min_)
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: min(min_), max(min_ * 10 - 1), power(logTen(min).value_or(-1))
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{
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}
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rep min;
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rep max;
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int power;
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};
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class Number
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{
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using uint128_t = numberuint128;
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using int128_t = numberint128;
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using rep = std::int64_t;
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using internalrep = MantissaRange::rep;
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internalrep mantissa_{0};
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int exponent_{std::numeric_limits<int>::lowest()};
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public:
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// The range for the exponent when normalized
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constexpr static int minExponent = -32768;
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constexpr static int maxExponent = 32768;
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// May need to make unchecked private
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struct unchecked
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{
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explicit unchecked() = default;
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};
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explicit constexpr Number() = default;
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Number(rep mantissa);
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explicit Number(internalrep mantissa, int exponent);
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explicit constexpr Number(
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internalrep mantissa,
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int exponent,
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unchecked) noexcept;
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constexpr internalrep
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mantissa() const noexcept;
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constexpr int
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exponent() const noexcept;
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constexpr Number
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operator+() const noexcept;
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constexpr Number
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operator-() const noexcept;
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Number&
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operator++();
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Number
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operator++(int);
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Number&
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operator--();
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Number
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operator--(int);
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Number&
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operator+=(Number const& x);
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Number&
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operator-=(Number const& x);
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Number&
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operator*=(Number const& x);
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Number&
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operator/=(Number const& x);
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static constexpr Number
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min(MantissaRange const& range) noexcept;
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static constexpr Number
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max(MantissaRange const& range) noexcept;
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static constexpr Number
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lowest(MantissaRange const& range) noexcept;
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/** Conversions to Number are implicit and conversions away from Number
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* are explicit. This design encourages and facilitates the use of Number
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* as the preferred type for floating point arithmetic as it makes
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* "mixed mode" more convenient, e.g. MPTAmount + Number.
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*/
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explicit
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operator rep() const; // round to nearest, even on tie
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friend constexpr bool
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operator==(Number const& x, Number const& y) noexcept
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{
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return x.mantissa_ == y.mantissa_ && x.exponent_ == y.exponent_;
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}
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friend constexpr bool
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operator!=(Number const& x, Number const& y) noexcept
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{
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return !(x == y);
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}
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friend constexpr bool
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operator<(Number const& x, Number const& y) noexcept
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{
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// If the two amounts have different signs (zero is treated as positive)
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// then the comparison is true iff the left is negative.
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bool const lneg = x.mantissa_ < 0;
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bool const rneg = y.mantissa_ < 0;
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if (lneg != rneg)
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return lneg;
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// Both have same sign and the left is zero: the right must be
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// greater than 0.
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if (x.mantissa_ == 0)
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return y.mantissa_ > 0;
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// Both have same sign, the right is zero and the left is non-zero.
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if (y.mantissa_ == 0)
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return false;
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// Both have the same sign, compare by exponents:
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if (x.exponent_ > y.exponent_)
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return lneg;
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if (x.exponent_ < y.exponent_)
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return !lneg;
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// If equal exponents, compare mantissas
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return x.mantissa_ < y.mantissa_;
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}
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/** Return the sign of the amount */
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constexpr int
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signum() const noexcept
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{
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return (mantissa_ < 0) ? -1 : (mantissa_ ? 1 : 0);
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}
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Number
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truncate() const noexcept
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{
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if (exponent_ >= 0 || mantissa_ == 0)
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return *this;
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Number ret = *this;
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while (ret.exponent_ < 0 && ret.mantissa_ != 0)
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{
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ret.exponent_ += 1;
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ret.mantissa_ /= rep(10);
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}
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// We are guaranteed that normalize() will never throw an exception
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// because exponent is either negative or zero at this point.
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ret.normalize();
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return ret;
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}
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friend constexpr bool
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operator>(Number const& x, Number const& y) noexcept
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{
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return y < x;
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}
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friend constexpr bool
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operator<=(Number const& x, Number const& y) noexcept
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{
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return !(y < x);
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}
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friend constexpr bool
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operator>=(Number const& x, Number const& y) noexcept
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{
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return !(x < y);
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}
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friend std::ostream&
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operator<<(std::ostream& os, Number const& x)
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{
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return os << to_string(x);
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}
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// Thread local rounding control. Default is to_nearest
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enum rounding_mode { to_nearest, towards_zero, downward, upward };
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static rounding_mode
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getround();
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// Returns previously set mode
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static rounding_mode
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setround(rounding_mode mode);
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static void
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setLargeMantissa(bool large);
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inline static internalrep
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minMantissa()
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{
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return range_.get().min;
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}
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inline static internalrep
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maxMantissa()
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{
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return range_.get().max;
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}
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inline static internalrep
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mantissaPower()
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{
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return range_.get().power;
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}
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constexpr static Number
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oneSmall();
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constexpr static Number
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oneLarge();
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static Number
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one();
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template <class T>
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[[nodiscard]]
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std::pair<T, int>
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normalizeToRange(T minMantissa, T maxMantissa) const;
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private:
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static thread_local rounding_mode mode_;
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// The available ranges for mantissa
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constexpr static MantissaRange smallRange{1'000'000'000'000'000LL};
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static_assert(isPowerOfTen(smallRange.min));
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static_assert(smallRange.max == 9'999'999'999'999'999LL);
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// maxint64 9,223,372,036,854,775,808
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constexpr static MantissaRange largeRange{1'000'000'000'000'000'000LL};
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static_assert(isPowerOfTen(largeRange.min));
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static_assert(largeRange.max == internalrep(9'999'999'999'999'999'999ULL));
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static_assert(largeRange.min < std::numeric_limits<std::int64_t>::max());
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static_assert(largeRange.max > std::numeric_limits<std::int64_t>::max());
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// The range for the mantissa when normalized.
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// Use reference_wrapper to avoid making copies, and prevent accidentally
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// changing the values inside the range.
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static thread_local std::reference_wrapper<MantissaRange const> range_;
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void
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normalize();
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static void
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normalize(
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internalrep& mantissa,
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int& exponent,
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internalrep const& minMantissa,
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internalrep const& maxMantissa);
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constexpr bool
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isnormal(MantissaRange const& range) const noexcept;
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friend Number
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root(Number f, unsigned d);
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friend Number
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root2(Number f);
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class Guard;
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};
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inline constexpr Number::Number(
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internalrep mantissa,
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int exponent,
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unchecked) noexcept
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: mantissa_{mantissa}, exponent_{exponent}
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{
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}
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inline Number::Number(internalrep mantissa, int exponent)
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: mantissa_{mantissa}, exponent_{exponent}
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{
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normalize();
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}
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inline Number::Number(rep mantissa) : Number{mantissa, 0}
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{
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}
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inline constexpr Number::internalrep
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Number::mantissa() const noexcept
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{
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return mantissa_;
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}
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inline constexpr int
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Number::exponent() const noexcept
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{
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return exponent_;
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}
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inline constexpr Number
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Number::operator+() const noexcept
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{
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return *this;
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}
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inline constexpr Number
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Number::operator-() const noexcept
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{
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auto x = *this;
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x.mantissa_ = -x.mantissa_;
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return x;
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}
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inline Number&
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Number::operator++()
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{
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*this += Number{1000000000000000, -15, unchecked{}};
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return *this;
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}
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inline Number
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Number::operator++(int)
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{
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auto x = *this;
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++(*this);
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return x;
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}
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inline Number&
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Number::operator--()
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{
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*this -= Number{1000000000000000, -15, unchecked{}};
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return *this;
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}
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inline Number
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Number::operator--(int)
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{
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auto x = *this;
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--(*this);
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return x;
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}
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inline Number&
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Number::operator-=(Number const& x)
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{
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return *this += -x;
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}
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inline Number
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operator+(Number const& x, Number const& y)
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{
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auto z = x;
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z += y;
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return z;
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}
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inline Number
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operator-(Number const& x, Number const& y)
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{
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auto z = x;
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z -= y;
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return z;
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}
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inline Number
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operator*(Number const& x, Number const& y)
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{
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auto z = x;
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z *= y;
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return z;
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}
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inline Number
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operator/(Number const& x, Number const& y)
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{
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auto z = x;
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z /= y;
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return z;
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}
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inline constexpr Number
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Number::min(MantissaRange const& range) noexcept
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{
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return Number{range.min, minExponent, unchecked{}};
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}
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inline constexpr Number
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Number::max(MantissaRange const& range) noexcept
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{
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return Number{range.max, maxExponent, unchecked{}};
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}
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inline constexpr Number
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Number::lowest(MantissaRange const& range) noexcept
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{
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return -Number{range.max, maxExponent, unchecked{}};
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}
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inline constexpr bool
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Number::isnormal(MantissaRange const& range) const noexcept
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{
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auto const abs_m = mantissa_ < 0 ? -mantissa_ : mantissa_;
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return range.min <= abs_m && abs_m <= range.max &&
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minExponent <= exponent_ && exponent_ <= maxExponent;
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}
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template <class T>
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std::pair<T, int>
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Number::normalizeToRange(T minMantissa, T maxMantissa) const
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{
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internalrep mantissa = mantissa_;
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int exponent = exponent_;
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Number::normalize(mantissa, exponent, minMantissa, maxMantissa);
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return std::make_pair(static_cast<T>(mantissa), exponent);
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}
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inline constexpr Number
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abs(Number x) noexcept
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{
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if (x < Number{})
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x = -x;
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return x;
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}
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// Returns f^n
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// Uses a log_2(n) number of multiplications
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Number
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power(Number const& f, unsigned n);
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// Returns f^(1/d)
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// Uses Newton–Raphson iterations until the result stops changing
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// to find the root of the polynomial g(x) = x^d - f
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Number
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root(Number f, unsigned d);
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Number
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root2(Number f);
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// Returns f^(n/d)
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Number
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power(Number const& f, unsigned n, unsigned d);
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// Return 0 if abs(x) < limit, else returns x
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inline constexpr Number
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squelch(Number const& x, Number const& limit) noexcept
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{
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if (abs(x) < limit)
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return Number{};
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return x;
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}
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class saveNumberRoundMode
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{
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Number::rounding_mode mode_;
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public:
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~saveNumberRoundMode()
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{
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Number::setround(mode_);
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}
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explicit saveNumberRoundMode(Number::rounding_mode mode) noexcept
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: mode_{mode}
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{
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}
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saveNumberRoundMode(saveNumberRoundMode const&) = delete;
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saveNumberRoundMode&
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operator=(saveNumberRoundMode const&) = delete;
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};
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// saveNumberRoundMode doesn't do quite enough for us. What we want is a
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// Number::RoundModeGuard that sets the new mode and restores the old mode
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// when it leaves scope. Since Number doesn't have that facility, we'll
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// build it here.
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class NumberRoundModeGuard
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{
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saveNumberRoundMode saved_;
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public:
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explicit NumberRoundModeGuard(Number::rounding_mode mode) noexcept
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: saved_{Number::setround(mode)}
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{
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}
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NumberRoundModeGuard(NumberRoundModeGuard const&) = delete;
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NumberRoundModeGuard&
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operator=(NumberRoundModeGuard const&) = delete;
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};
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} // namespace ripple
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#endif // XRPL_BASICS_NUMBER_H_INCLUDED
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