128 lines
2.3 KiB
C++
128 lines
2.3 KiB
C++
//
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// Created by erki on 27.03.21.
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//
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#ifndef SKULLC_MESSAGING_PARSER_HPP
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#define SKULLC_MESSAGING_PARSER_HPP
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#include <array>
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#include <cstdint>
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#include <cstring>
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namespace Messaging
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{
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template<typename P, typename std::size_t N>
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class Parser
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{
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public:
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using Packet = P;
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const std::size_t buffer_length = N;
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Parser() { reset(); }
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Parser(const Parser&) = delete;
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Parser(Parser&&) = delete;
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void reset()
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{
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_state = _State::Preamble;
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_expected = sizeof(P::preamble);
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_current_pos = 0;
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_current_offset = 0;
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}
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void pushByte(const std::uint8_t byte)
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{
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if (packetReady())
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return;
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const std::uint32_t buffer_loc = _current_offset + _current_pos;
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switch (_state)
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{
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case _State::Preamble:
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if (byte != P::preamble[_current_pos])
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{
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reset();
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return;
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}
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[[fallthrough]];
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case _State::Length:
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case _State::Body:
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_buffer[buffer_loc] = byte;
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_current_pos++;
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break;
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default:
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break;
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}
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if (_current_pos == _expected)
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{
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_setupNextState();
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}
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}
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bool packetReady() const { return _state == _State::Done; }
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bool getPacket(Packet& packet) const
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{
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return packet.deserialize(_buffer.data(), _current_offset);
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}
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private:
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enum class _State : std::uint32_t
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{
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Preamble,
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Length,
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Body,
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Done
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};
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std::array<std::uint8_t, N> _buffer;
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_State _state = _State::Preamble;
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std::uint32_t _current_pos = 0;
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std::uint32_t _current_offset = 0;
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std::uint32_t _expected = 0;
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template<typename T>
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T _deserializeLength(const std::uint32_t offset)
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{
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std::uint8_t* begin = _buffer.data() + offset;
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T len(0);
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std::memcpy(&len, begin, sizeof(T));
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return len;
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}
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void _setupNextState()
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{
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switch (_state)
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{
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case _State::Preamble:
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_state = _State::Length;
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_expected = sizeof(typename P::length_type);
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break;
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case _State::Length:
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_state = _State::Body;
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_expected = _deserializeLength<typename P::length_type>(_current_offset);
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break;
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case _State::Body:
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_state = _State::Done;
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break;
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default:
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break;
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}
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_current_offset += _current_pos;
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_current_pos = 0;
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}
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};
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}// namespace Messaging
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#endif// SKULLC_MESSAGING_PARSER_HPP
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