fluxengine/arch/northstar/encoder.cc

#include "globals.h"
#include "northstar.h"
#include "sector.h"
#include "bytes.h"
#include "decoders/decoders.h"
#include "encoders/encoders.h"
#include "image.h"
#include "lib/encoders/encoders.pb.h"

#define GAP_FILL_SIZE_SD 30
#define PRE_HEADER_GAP_FILL_SIZE_SD 9
#define GAP_FILL_SIZE_DD 62
#define PRE_HEADER_GAP_FILL_SIZE_DD 16

#define GAP1_FILL_BYTE (0x4F)
#define GAP2_FILL_BYTE (0x4F)

#define TOTAL_SECTOR_BYTES ()

static void write_sector(std::vector<bool>& bits,
    unsigned& cursor,
    const std::shared_ptr<const Sector>& sector)
{
    int preambleSize = 0;
    int encodedSectorSize = 0;
    int preHeaderGapFillSize = 0;

    bool doubleDensity;

    switch (sector->data.size())
    {
        case NORTHSTAR_PAYLOAD_SIZE_SD:
            preambleSize = NORTHSTAR_PREAMBLE_SIZE_SD;
            encodedSectorSize = PRE_HEADER_GAP_FILL_SIZE_SD +
                                NORTHSTAR_ENCODED_SECTOR_SIZE_SD;
            preHeaderGapFillSize = PRE_HEADER_GAP_FILL_SIZE_SD;
            doubleDensity = false;
            break;

        case NORTHSTAR_PAYLOAD_SIZE_DD:
            preambleSize = NORTHSTAR_PREAMBLE_SIZE_DD;
            encodedSectorSize = PRE_HEADER_GAP_FILL_SIZE_DD +
                                NORTHSTAR_ENCODED_SECTOR_SIZE_DD;
            preHeaderGapFillSize = PRE_HEADER_GAP_FILL_SIZE_DD;
            doubleDensity = true;
            break;

        default:
            Error() << "unsupported sector size --- you must pick 256 or 512";
            break;
    }

    int fullSectorSize = preambleSize + encodedSectorSize;
    auto fullSector = std::make_shared<std::vector<uint8_t>>();
    fullSector->reserve(fullSectorSize);

    /* sector gap after index pulse */
    for (int i = 0; i < preHeaderGapFillSize; i++)
        fullSector->push_back(GAP1_FILL_BYTE);

    /* sector preamble */
    for (int i = 0; i < preambleSize; i++)
        fullSector->push_back(0);

    Bytes sectorData;
    if (sector->data.size() == encodedSectorSize)
        sectorData = sector->data;
    else
    {
        ByteWriter writer(sectorData);
        writer.write_8(0xFB); /* sync character */
        if (doubleDensity == true)
            writer.write_8(0xFB); /* Double-density has two sync characters */

        writer += sector->data;
        if (doubleDensity == true)
            writer.write_8(northstarChecksum(sectorData.slice(2)));
        else
            writer.write_8(northstarChecksum(sectorData.slice(1)));
    }
    for (uint8_t b : sectorData)
        fullSector->push_back(b);

    if (fullSector->size() != fullSectorSize)
        Error() << "sector mismatched length (" << sector->data.size()
                << ") expected: " << fullSector->size() << " got "
                << fullSectorSize;

    /* A few bytes of sector postamble just so the blank skip area doesn't start
     * immediately after the data. */

    for (int i = 0; i < 10; i++)
        fullSector->push_back(GAP2_FILL_BYTE);

    bool lastBit = false;

    if (doubleDensity == true)
        encodeMfm(bits, cursor, fullSector, lastBit);
    else
        encodeFm(bits, cursor, fullSector);
}

class NorthstarEncoder : public AbstractEncoder
{
public:
    NorthstarEncoder(const EncoderProto& config):
        AbstractEncoder(config),
        _config(config.northstar())
    {
    }

    std::vector<std::shared_ptr<const Sector>> collectSectors(
        int physicalTrack, int physicalSide, const Image& image) override
    {
        std::vector<std::shared_ptr<const Sector>> sectors;

        if ((physicalTrack >= 0) && (physicalTrack < 35))
        {
            for (int sectorId = 0; sectorId < 10; sectorId++)
            {
                const auto& sector =
                    image.get(physicalTrack, physicalSide, sectorId);
                if (sector)
                    sectors.push_back(sector);
            }
        }

        return sectors;
    }

    std::unique_ptr<Fluxmap> encode(int physicalTrack,
        int physicalSide,
        const std::vector<std::shared_ptr<const Sector>>& sectors,
        const Image& image) override
    {
        int bitsPerRevolution = 100000;
        double clockRateUs = 4.00;

        if ((physicalTrack < 0) || (physicalTrack >= 35) || sectors.empty())
            return std::unique_ptr<Fluxmap>();

        const auto& sector = *sectors.begin();
        if (sector->data.size() == NORTHSTAR_PAYLOAD_SIZE_SD)
            bitsPerRevolution /= 2; // FM
        else
            clockRateUs /= 2.00;

        auto fluxmap = std::make_unique<Fluxmap>();
		bool first = true;
        for (const auto& sectorData : sectors)
        {
			if (!first)
				fluxmap->appendIndex();
			first = false;

            std::vector<bool> bits(bitsPerRevolution);
            unsigned cursor = 0;
            write_sector(bits, cursor, sectorData);
            fluxmap->appendBits(bits, clockRateUs * 1e3);
        }

//        if (fluxmap->duration() > 200e6)
//            Error() << "track data overrun";

        return fluxmap;
    }

private:
    const NorthstarEncoderProto& _config;
};

std::unique_ptr<AbstractEncoder> createNorthstarEncoder(
    const EncoderProto& config)
{
    return std::unique_ptr<AbstractEncoder>(new NorthstarEncoder(config));
}