satdump/src-core/common/lrit/lrit_demux.cpp

#include "lrit_demux.h"
#include "common/ccsds/ccsds_weather/vcdu.h"
#include "logger.h"
#include "crc_table.h"

namespace lrit
{
    LRITDemux::LRITDemux(int mpdu_size, bool check_crc) : d_mpdu_size(mpdu_size), d_check_crc(check_crc)
    {
    }

    LRITDemux::~LRITDemux()
    {
    }

    // CRC Implementation from LRIT-Mission-Specific-Document.pdf
    uint16_t computeCRC(const uint8_t *data, int size)
    {
        uint16_t crc = 0xffff;
        for (int i = 0; i < size; i++)
            crc = (crc << 8) ^ crc_table[(crc >> 8) ^ (uint16_t)data[i]];
        return crc;
    }

    std::vector<LRITFile> LRITDemux::work(uint8_t *cadu)
    {
        files.clear();

        ccsds::ccsds_weather::VCDU vcdu = ccsds::ccsds_weather::parseVCDU(cadu);

        if (vcdu.vcid == 63) // Skip filler
            return files;

        if (demuxers.count(vcdu.vcid) <= 0) // Add new demux if required
        {
            demuxers.emplace(std::pair<int, std::unique_ptr<ccsds::ccsds_weather::Demuxer>>(vcdu.vcid, std::make_unique<ccsds::ccsds_weather::Demuxer>(d_mpdu_size, false)));
            wip_files.insert({vcdu.vcid, std::map<int, LRITFile>()});
        }

        // Demux
        std::vector<ccsds::CCSDSPacket> ccsdsFrames = demuxers[vcdu.vcid]->work(cadu);

        for (ccsds::CCSDSPacket &pkt : ccsdsFrames)
        {
            if (pkt.header.apid == 2047 || pkt.payload.size() < 2) // Skip filler
                continue;

            if (wip_files[vcdu.vcid].count(pkt.header.apid) == 0) // One file per APID
                wip_files[vcdu.vcid].insert({pkt.header.apid, LRITFile()});

            LRITFile &current_file = wip_files[vcdu.vcid][pkt.header.apid];

            // Check CRC
            uint16_t crc = pkt.payload.data()[pkt.payload.size() - 2] << 8 | pkt.payload.data()[pkt.payload.size() - 1];
            if (d_check_crc ? !(crc == computeCRC(pkt.payload.data(), pkt.payload.size() - 2)) : false)
            {
                //If this is the middle of a file, we have the header, and it's an image, continue on failure
                bool can_continue = false;
                if (current_file.file_in_progress && pkt.header.sequence_flag == 0 && current_file.header_parsed)
                {
                    PrimaryHeader primary_header = current_file.getHeader<PrimaryHeader>();
                    can_continue = primary_header.file_type_code == 0 && current_file.hasHeader<ImageStructureRecord>();
                }

                if (can_continue)
                {
                    logger->warn("LRIT CRC is invalid, but file can be recovered");
                    processLRITData(current_file, pkt); //Push anyway - there's probably some good pixels in there
                }
                else
                {
                    logger->error("LRIT CRC is invalid... Skipping.");
                    current_file.file_in_progress = false;
                }
                continue;
            }

            if (pkt.header.sequence_flag == 1 || pkt.header.sequence_flag == 3)
            {
                if (current_file.file_in_progress)
                    finalizeLRITData(current_file);

                current_file.lrit_data.clear();

                processLRITHeader(current_file, pkt);
                current_file.vcid = vcdu.vcid;
                current_file.header_parsed = false;
                current_file.file_in_progress = true;
            }
            else if (pkt.header.sequence_flag == 0)
            {
                if (current_file.file_in_progress)
                    processLRITData(current_file, pkt);
            }
            else if (pkt.header.sequence_flag == 2)
            {
                if (current_file.file_in_progress)
                {
                    processLRITData(current_file, pkt);
                    finalizeLRITData(current_file);
                    current_file.file_in_progress = false;
                }
            }

            if (current_file.file_in_progress && !current_file.header_parsed)
            {
                PrimaryHeader primary_header = current_file.getHeader<PrimaryHeader>();

                if (current_file.lrit_data.size() >= primary_header.total_header_length)
                {
                    parseHeader(current_file);
                    current_file.header_parsed = true;
                }
            }
        }

        return files;
    }

    void LRITDemux::processLRITHeader(LRITFile &file, ccsds::CCSDSPacket &pkt)
    {
        file.lrit_data.insert(file.lrit_data.end(), &pkt.payload.data()[10], &pkt.payload.data()[pkt.payload.size() - 2]);
    }

    void LRITDemux::parseHeader(LRITFile &file)
    {
        file.parseHeaders();
        logger->info("New LRIT file : " + file.filename);
        onParseHeader(file);
    }

    void LRITDemux::processLRITData(LRITFile &file, ccsds::CCSDSPacket &pkt)
    {
        if (onProcessData(file, pkt))
            file.lrit_data.insert(file.lrit_data.end(), &pkt.payload.data()[0], &pkt.payload.data()[pkt.payload.size() - 2]);
    }

    void LRITDemux::finalizeLRITData(LRITFile &file)
    {
        onFinalizeData(file);
        files.push_back(file);
    }
};