97 lines
3.0 KiB
C++
97 lines
3.0 KiB
C++
//-----------------------------------------------------------------------------
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// ___ __ _ _
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// / _ \__ _ _ __ ___ ___ / /(_)_ __ | | __
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// / /_)/ _` | '__/ __|/ _ \/ / | | '_ \| |/ /
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// / ___/ (_| | | \__ \ __/ /__| | | | | <
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// \/ \__,_|_| |___/\___\____/_|_| |_|_|\_\ .
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//
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//-----------------------------------------------------------------------------
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// Author: Kurt Sassenrath
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// Module: msgpack
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//
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// Default packer implementation, which aims to deduce the best format to use
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// for a given value. For example, if a 32-bit unsigned integer type only
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// contains the value 5, a uint32 format would serialize into:
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//
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// 0xce, 0x00, 0x00, 0x00, 0x05
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//
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// Instead, the packer will note that this value could be stored in a positive
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// fixint, which is simply:
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//
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// 0x05
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//
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// The same optimization will be applied to variable-length types, like strings,
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// bytes, arrays, and maps.
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//
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// This flexibility comes at the cost of CPU instructions. For embedded targets,
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// writer (to be renamed verbatim_packer in the future) may be a better choice.
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//
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// Future goals for this particular packer:
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// 1. Support containers/ranges seamlessly.
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// 2. Support packing of trivial POD structures without an explicit
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// pack_adapter.
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//
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// Copyright (c) 2023 Kurt Sassenrath.
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//
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// License TBD.
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//-----------------------------------------------------------------------------
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#ifndef msgpack_core_packer_1d5939e9c1498568
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#define msgpack_core_packer_1d5939e9c1498568
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#include "parselink/msgpack/core/detail/builtin_packable_types.h"
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#include "parselink/msgpack/core/error.h"
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#include "parselink/msgpack/core/format.h"
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#include "parselink/msgpack/util/endianness.h"
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#include <tl/expected.hpp>
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#include <limits>
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#include <type_traits>
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namespace msgpack {
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template <typename T>
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struct pack_adapter {};
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template <typename T>
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concept packable_type = builtin_packable<T>;
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class packer {
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// Replace with output_range?
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using BufferType = std::span<std::byte>;
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public:
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constexpr packer(BufferType buff)
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: buff_(buff)
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, curr_(std::begin(buff_))
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, end_(std::end(buff_)) {}
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template <packable_type T>
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constexpr tl::expected<tl::monostate, error> pack(T&& v) noexcept {
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using diff_type =
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std::iterator_traits<decltype(curr_)>::difference_type;
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diff_type const space_needed = builtin_packer<T>::total_size(v);
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if (space_needed > std::distance(curr_, end_)) {
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return tl::make_unexpected(error::out_of_space);
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} else {
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curr_ = builtin_packer<T>::pack(v, curr_);
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return tl::monostate{};
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}
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}
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constexpr auto tell() const noexcept {
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return std::distance(std::begin(buff_), curr_);
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}
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constexpr auto subspan() const noexcept { return buff_.subspan(0, tell()); }
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private:
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BufferType buff_;
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decltype(std::begin(buff_)) curr_;
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decltype(std::end(buff_)) end_;
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};
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} // namespace msgpack
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#endif // msgpack_core_packer_1d5939e9c1498568
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