satdump/src-core/modules/goes/gvar/gvar_deframer.cpp

#include "gvar_deframer.h"

#include <math.h>

// Returns the asked bit!
template <typename T>
inline bool getBit(T &data, int &bit)
{
    return (data >> bit) & 1;
}

namespace goes
{
    namespace gvar
    {
        // Compare 2 32-bits values bit per bit
        int checkSyncMarker(uint64_t marker, uint64_t &totest)
        {
            int errors = 0;
            for (int i = 63; i >= 0; i--)
            {
                bool markerBit, testBit;
                markerBit = getBit<uint64_t>(marker, i);
                testBit = getBit<uint64_t>(totest, i);
                if (markerBit != testBit)
                    errors++;

                if (errors >= 10)
                    return errors;
            }
            return errors;
        }

        template <typename SYNC_T, int SYNC_SIZE, int FRAME_SIZE, SYNC_T ASM_SYNC>
        GVARDeframer<SYNC_T, SYNC_SIZE, FRAME_SIZE, ASM_SYNC>::GVARDeframer()
        {
            // Default values
            writeFrame = false;
            wroteBits = 0;
            outputBits = 0;
        }

        // Write a single bit into the frame
        template <typename SYNC_T, int SYNC_SIZE, int FRAME_SIZE, SYNC_T ASM_SYNC>
        void GVARDeframer<SYNC_T, SYNC_SIZE, FRAME_SIZE, ASM_SYNC>::pushBit(uint8_t bit)
        {
            byteBuffer = (byteBuffer << 1) | bit;
            wroteBits++;
            if (wroteBits == 8)
            {
                frameBuffer.push_back(byteBuffer);
                wroteBits = 0;
            }
        }

        template <typename SYNC_T, int SYNC_SIZE, int FRAME_SIZE, SYNC_T ASM_SYNC>
        std::vector<std::vector<uint8_t>> GVARDeframer<SYNC_T, SYNC_SIZE, FRAME_SIZE, ASM_SYNC>::work(uint8_t *data, int len)
        {
            // Output buffer
            std::vector<std::vector<uint8_t>> framesOut;

            // Loop in all bytes
            for (int byten = 0; byten < len; byten++)
            {
                uint8_t &byte = data[byten];

                // Loop in all bits!
                for (int i = 7; i >= 0; i--)
                {
                    // Get a bit, push it
                    uint8_t bit = getBit<uint8_t>(byte, i);

                    if (sizeof(SYNC_T) * 8 != SYNC_SIZE)
                        shifter = ((shifter << 1) % (long)pow(2, SYNC_SIZE)) | bit;
                    else
                        shifter = (shifter << 1) | bit;

                    // Writing a frame!
                    if (writeFrame)
                    {
                        // First run : push header
                        if (outputBits == 0)
                        {
                            SYNC_T syncAsm = ASM_SYNC;
                            for (int y = SYNC_SIZE - 1; y >= 0; y--)
                            {
                                pushBit(getBit<SYNC_T>(syncAsm, y));
                                outputBits++;
                            }
                        }

                        // New ASM, ABORT! and process the new one
                        if (outputBits > 10000)
                            if (checkSyncMarker(ASM_SYNC, shifter) < 10)
                            {
                                // Fill up what we're missing
                                for (int b = 0; b < FRAME_SIZE - outputBits; b++)
                                    pushBit(0);

                                writeFrame = false;
                                wroteBits = 0;
                                outputBits = 0;
                                framesOut.push_back(frameBuffer);
                                frameBuffer.clear();

                                writeFrame = true;

                                continue;
                            }

                        // Push current bit
                        pushBit(bit);
                        outputBits++;

                        // Once we wrote a frame, exit!
                        if (outputBits == FRAME_SIZE)
                        {
                            writeFrame = false;
                            wroteBits = 0;
                            outputBits = 0;
                            framesOut.push_back(frameBuffer);
                            frameBuffer.clear();
                        }

                        continue;
                    }

                    // Otherwise search for markers
                    if (checkSyncMarker(ASM_SYNC, shifter) < 10)
                    {
                        writeFrame = true;
                    }
                }
            }

            // Output what we found if anything
            return framesOut;
        }

        // Build this template for GVAR data
        template class GVARDeframer<uint64_t, 64, 262288, 0b0001101111100111110100000001111110111111100000001111111111111110>;
    }
}