kopia lustrzana https://github.com/OpenRTX/OpenRTX
152 wiersze
4.9 KiB
C++
152 wiersze
4.9 KiB
C++
/***************************************************************************
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* Copyright (C) 2022 - 2023 by Federico Amedeo Izzo IU2NUO, *
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* Niccolò Izzo IU2KIN *
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* Frederik Saraci IU2NRO *
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* Silvano Seva IU2KWO *
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 3 of the License, or *
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* (at your option) any later version. *
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* *
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* This program is distributed in the hope that it will be useful, *
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* but WITHOUT ANY WARRANTY; without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
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* GNU General Public License for more details. *
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* *
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* You should have received a copy of the GNU General Public License *
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* along with this program; if not, see <http://www.gnu.org/licenses/> *
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***************************************************************************/
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#ifndef M17FRAMEDECODER_H
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#define M17FRAMEDECODER_H
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#ifndef __cplusplus
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#error This header is C++ only!
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#endif
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#include <cstdint>
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#include <string>
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#include <array>
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#include "M17LinkSetupFrame.hpp"
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#include "M17Viterbi.hpp"
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#include "M17StreamFrame.hpp"
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namespace M17
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{
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enum class M17FrameType : uint8_t
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{
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PREAMBLE = 0, ///< Frame contains a preamble.
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LINK_SETUP = 1, ///< Frame is a Link Setup Frame.
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STREAM = 2, ///< Frame is a stream data frame.
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PACKET = 3, ///< Frame is a packet data frame.
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UNKNOWN = 4 ///< Frame is unknown.
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};
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/**
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* M17 frame decoder.
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*/
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class M17FrameDecoder
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{
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public:
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/**
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* Constructor.
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*/
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M17FrameDecoder();
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/**
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* Destructor.
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*/
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~M17FrameDecoder();
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/**
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* Clear the internal data structures.
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*/
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void reset();
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/**
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* Decode an M17 frame, identifying its type. Frame data must contain the
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* sync word in the first two bytes.
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*
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* @param frame: byte array containg frame data.
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* @return the type of frame recognized.
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*/
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M17FrameType decodeFrame(const frame_t& frame);
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/**
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* Get the latest Link Setup Frame decoded. Check of the validity of the
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* data contained in the LSF is left to application code.
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*
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* @return a reference to the latest Link Setup Frame decoded.
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*/
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const M17LinkSetupFrame& getLsf()
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{
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return lsf;
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}
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/**
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* Get the latest stream data frame decoded.
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*
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* @return a reference to the latest stream data frame decoded.
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*/
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const M17StreamFrame& getStreamFrame()
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{
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return streamFrame;
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}
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private:
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/**
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* Determine frame type by searching which syncword among the standard M17
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* ones has the minumum hamming distance from the given one. If the hamming
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* distance exceeds a masimum absolute threshold the frame is declared of
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* unknown type.
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*
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* @param syncWord: frame syncword.
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* @return frame type based on the given syncword.
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*/
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M17FrameType getFrameType(const std::array< uint8_t, 2 >& syncWord);
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/**
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* Decode Link Setup Frame data and update the internal LSF field with
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* the new frame data.
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*
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* @param data: byte array containg frame data, without sync word.
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*/
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void decodeLSF(const std::array< uint8_t, 46 >& data);
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/**
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* Decode stream data and update the internal LSF field with the new
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* frame data.
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*
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* @param data: byte array containg frame data, without sync word.
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*/
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void decodeStream(const std::array< uint8_t, 46 >& data);
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/**
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* Decode a LICH block.
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*
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* @param segment: byte array where to store the decoded Link Setup Frame
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* segment. The last byte contains the segment number.
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* @param lich: LICH block to be decoded.
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* @return true when the LICH block is successfully decoded.
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*/
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bool decodeLich(std::array< uint8_t, 6 >& segment, const lich_t& lich);
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uint8_t lsfSegmentMap; ///< Bitmap for LSF reassembly from LICH
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M17LinkSetupFrame lsf; ///< Latest LSF received.
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M17LinkSetupFrame lsfFromLich; ///< LSF assembled from LICH segments.
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M17StreamFrame streamFrame; ///< Latest stream dat frame received.
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M17HardViterbi viterbi; ///< Viterbi decoder.
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///< Maximum allowed hamming distance when determining the frame type.
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static constexpr uint8_t MAX_SYNC_HAMM_DISTANCE = 4;
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};
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} // namespace M17
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#endif // M17FRAMEDECODER_H
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