big_decimal.hh

/*
 * Copyright (C) 2015-present ScyllaDB
 */

/*
 * SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.0
 */

#pragma once

#include "multiprecision_int.hh"
#include <boost/multiprecision/fwd.hpp>
#include <seastar/core/sstring.hh>
#include <compare>
#include <concepts>

using seastar::sstring;

uint64_t from_varint_to_integer(const utils::multiprecision_int& varint);

class big_decimal {
private:
    int32_t _scale;
    boost::multiprecision::cpp_int _unscaled_value;

private:
    std::strong_ordering tri_cmp_slow(const big_decimal& other) const;
    std::strong_ordering tri_cmp_positive_nonzero_different_scale(const big_decimal& other) const;

public:
    enum class rounding_mode {
        HALF_EVEN,
    };

    explicit big_decimal(std::string_view text);
    big_decimal();
    big_decimal(int32_t scale, boost::multiprecision::cpp_int unscaled_value);
    big_decimal(std::integral auto v) : big_decimal(0, v) {}

    int32_t scale() const { return _scale; }
    const boost::multiprecision::cpp_int& unscaled_value() const { return _unscaled_value; }
    boost::multiprecision::cpp_rational as_rational() const;

    sstring to_string() const;

    std::strong_ordering operator<=>(const big_decimal& other) const;

    big_decimal& operator+=(const big_decimal& other);
    big_decimal& operator-=(const big_decimal& other);
    big_decimal operator+(const big_decimal& other) const;
    big_decimal operator-(const big_decimal& other) const;
    big_decimal operator-() const;
    big_decimal div(const ::uint64_t y, const rounding_mode mode) const;
};

template <>
struct fmt::formatter<big_decimal> : fmt::formatter<string_view> {
    template <typename FormatContext>
    auto format(const big_decimal& v, FormatContext& ctx) const {
        return fmt::format_to(ctx.out(), "{}", v.to_string());
    }
};