142 lines
5.8 KiB
C++
142 lines
5.8 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/traits.h"
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//! A required field has the same key name and C/C++ name
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#define WIRE_FIELD(name) \
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::wire::field( #name , std::ref( self . name ))
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//! A required field has the same key name and C/C++ name AND is cheap to copy (faster output).
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#define WIRE_FIELD_COPY(name) \
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::wire::field( #name , self . name )
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//! The optional field has the same key name and C/C++ name
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#define WIRE_OPTIONAL_FIELD(name) \
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::wire::optional_field( #name , std::ref( self . name ))
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namespace wire
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{
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/*! Links `name` to a `value` for object serialization.
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`value_type` is `T` with optional `std::reference_wrapper` removed.
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`value_type` needs a `read_bytes` function when parsing with a
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`wire::reader` - see `read.h` for more info. `value_type` needs a
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`write_bytes` function when writing with a `wire::writer` - see `write.h`
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for more info.
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Any `value_type` where `is_optional_on_empty<value_type> == true`, will
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automatically be converted to an optional field iff `value_type` has an
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`empty()` method that returns `true`. The old output engine omitted fields
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when an array was empty, and the standard input macro would ignore the
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`false` return for the missing field. For compability reasons, the
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input/output engine here matches that behavior. See `wrapper/array.h` to
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enforce a required field even when the array is empty or specialize the
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`is_optional_on_empty` trait. Only new fields should use this behavior.
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Additional concept requirements for `value_type` when `Required == false`:
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* must have an `operator*()` function.
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* must have a conversion to bool function that returns true when
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`operator*()` is safe to call (and implicitly when the associated field
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should be written as opposed to skipped/omitted).
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Additional concept requirements for `value_type` when `Required == false`
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when reading:
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* must have an `emplace()` method that ensures `operator*()` is safe to call.
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* must have a `reset()` method to indicate a field was skipped/omitted.
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If a standard type needs custom serialization, one "trick":
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```
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struct custom_tag{};
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void read_bytes(wire::reader&, boost::fusion::pair<custom_tag, std::string&>)
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{ ... }
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void write_bytes(wire::writer&, boost::fusion::pair<custom_tag, const std::string&>)
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{ ... }
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template<typename F, typename T>
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void object_map(F& format, T& self)
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{
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wire::object(format,
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wire::field("foo", boost::fusion::make_pair<custom_tag>(std::ref(self.foo)))
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);
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}
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```
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Basically each input/output format needs a unique type so that the compiler
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knows how to "dispatch" the read/write calls. */
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template<typename T, bool Required>
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struct field_
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{
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using value_type = unwrap_reference_t<T>;
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//! \return True if field is forced optional when `get_value().empty()`.
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static constexpr bool optional_on_empty() noexcept
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{ return is_optional_on_empty<value_type>::value; }
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static constexpr bool is_required() noexcept { return Required && !optional_on_empty(); }
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static constexpr std::size_t count() noexcept { return 1; }
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const char* name;
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T value;
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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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};
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//! Links `name` to `value`. Use `std::ref` if de-serializing.
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template<typename T>
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constexpr inline field_<T, true> field(const char* name, T value)
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{
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return {name, std::move(value)};
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}
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//! Links `name` to optional `value`. Use `std::ref` if de-serializing.
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template<typename T>
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constexpr inline field_<T, false> optional_field(const char* name, T value)
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{
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return {name, std::move(value)};
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}
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template<typename T>
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inline constexpr bool available(const field_<T, true>& elem)
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{
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/* The old output engine always skipped fields when it was an empty array,
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this follows that behavior. See comments for `field_`. */
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return elem.is_required() || (elem.optional_on_empty() && !wire::empty(elem.get_value()));
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}
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template<typename T>
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inline constexpr bool available(const field_<T, false>& elem)
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{
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return bool(elem.get_value());
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}
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} // wire
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