78 lines
3.2 KiB
C++
78 lines
3.2 KiB
C++
// Copyright (c) 2021-2023, The Monero Project
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without modification, are
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// permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice, this list of
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// conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright notice, this list
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// of conditions and the following disclaimer in the documentation and/or other
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// materials provided with the distribution.
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//
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// 3. Neither the name of the copyright holder nor the names of its contributors may be
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// used to endorse or promote products derived from this software without specific
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// prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#pragma once
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#include <functional>
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#include <utility>
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#include "serialization/wire/field.h"
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#include "serialization/wire/traits.h"
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//! An optional field that is omitted when a default value is used
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#define WIRE_FIELD_DEFAULTED(name, default_) \
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::wire::optional_field( #name , ::wire::defaulted(std::ref( self . name ), default_ ))
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namespace wire
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{
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/*! A wrapper that tells `wire::writer`s to skip field generation when default
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value, and tells `wire::reader`s to use default value when field not present. */
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template<typename T, typename U>
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struct defaulted_
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{
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using value_type = unwrap_reference_t<T>;
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T value;
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U default_;
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constexpr const value_type& get_value() const noexcept { return value; }
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value_type& get_value() noexcept { return value; }
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// concept requirements for optional fields
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constexpr explicit operator bool() const { return get_value() != default_; }
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value_type& emplace() noexcept { return get_value(); }
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constexpr const value_type& operator*() const noexcept { return get_value(); }
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value_type& operator*() noexcept { return get_value(); }
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void reset() { get_value() = default_; }
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};
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//! Links `value` with `default_`.
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template<typename T, typename U>
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inline constexpr defaulted_<T, U> defaulted(T value, U default_)
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{
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return {std::move(value), std::move(default_)};
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}
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/* read/write functions not needed since `defaulted_` meets the concept
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requirements for an optional type (optional fields are handled
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directly by the generic read/write code because the field name is omitted
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entirely when the value is "empty"). */
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} // wire
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