monero/contrib/epee/include/serialization/wire/wrapper/defaulted.h
2024-05-21 16:29:33 +00:00

78 lines
3.2 KiB
C++

// Copyright (c) 2021-2024, The Monero Project
// All rights reserved.
//
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// permitted provided that the following conditions are met:
//
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// of conditions and the following disclaimer in the documentation and/or other
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#pragma once
#include <functional>
#include <utility>
#include "serialization/wire/field.h"
#include "serialization/wire/traits.h"
//! An optional field that is omitted when a default value is used
#define WIRE_FIELD_DEFAULTED(name, default_) \
::wire::optional_field( #name , ::wire::defaulted(std::ref( self . name ), default_ ))
namespace wire
{
/*! A wrapper that tells `wire::writer`s to skip field generation when default
value, and tells `wire::reader`s to use default value when field not present. */
template<typename T, typename U>
struct defaulted_
{
using value_type = unwrap_reference_t<T>;
T value;
U default_;
constexpr const value_type& get_value() const noexcept { return value; }
value_type& get_value() noexcept { return value; }
// concept requirements for optional fields
constexpr explicit operator bool() const { return get_value() != default_; }
value_type& emplace() noexcept { return get_value(); }
constexpr const value_type& operator*() const noexcept { return get_value(); }
value_type& operator*() noexcept { return get_value(); }
void reset() { get_value() = default_; }
};
//! Links `value` with `default_`.
template<typename T, typename U>
inline constexpr defaulted_<T, U> defaulted(T value, U default_)
{
return {std::move(value), std::move(default_)};
}
/* read/write functions not needed since `defaulted_` meets the concept
requirements for an optional type (optional fields are handled
directly by the generic read/write code because the field name is omitted
entirely when the value is "empty"). */
} // wire