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https://github.com/davidgiven/fluxengine.git
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Convert the Northstar decoder.
This commit is contained in:
David Given
@@ -18,6 +18,7 @@
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#include "sector.h"
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#include "northstar.h"
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#include "bytes.h"
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#include "lib/decoders/decoders.pb.h"
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#include "fmt/format.h"
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/*
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@@ -48,73 +49,6 @@ const FluxMatchers ANY_SECTOR_PATTERN(
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}
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);
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/* Search for FM or MFM sector record */
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AbstractDecoder::RecordType NorthstarDecoder::advanceToNextRecord()
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{
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nanoseconds_t now = _fmr->tell().ns();
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/* For all but the first sector, seek to the next sector pulse.
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* The first sector does not contain the sector pulse in the fluxmap.
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*/
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if (now != 0) {
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_fmr->seekToIndexMark();
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now = _fmr->tell().ns();
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}
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/* Discard a possible partial sector at the end of the track.
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* This partial sector could be mistaken for a conflicted sector, if
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* whatever data read happens to match the checksum of 0, which is
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* rare, but has been observed on some disks.
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*/
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if (now > (_fmr->getDuration() - 21e6)) {
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_fmr->seekToIndexMark();
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return(UNKNOWN_RECORD);
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}
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int msSinceIndex = std::round(now / 1e6);
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const FluxMatcher* matcher = nullptr;
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/* Note that the seekToPattern ignores the sector pulses, so if
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* a sector is not found for some reason, the seek will advance
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* past one or more sector pulses. For this reason, calculate
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* _hardSectorId after the sector header is found.
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*/
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_sector->clock = _fmr->seekToPattern(ANY_SECTOR_PATTERN, matcher);
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int sectorFoundTimeRaw = std::round((_fmr->tell().ns()) / 1e6);
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int sectorFoundTime;
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/* Round time to the nearest 20ms */
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if ((sectorFoundTimeRaw % 20) < 10) {
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sectorFoundTime = (sectorFoundTimeRaw / 20) * 20;
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}
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else {
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sectorFoundTime = ((sectorFoundTimeRaw + 20) / 20) * 20;
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}
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/* Calculate the sector ID based on time since the index */
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_hardSectorId = (sectorFoundTime / 20) % 10;
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// std::cout << fmt::format(
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// "Sector ID {}: hole at {}ms, sector start at {}ms",
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// _hardSectorId, msSinceIndex, sectorFoundTimeRaw) << std::endl;
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if (matcher == &MFM_PATTERN) {
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_sectorType = SECTOR_TYPE_MFM;
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readRawBits(48);
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return SECTOR_RECORD;
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}
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if (matcher == &FM_PATTERN) {
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_sectorType = SECTOR_TYPE_FM;
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readRawBits(48);
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return SECTOR_RECORD;
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}
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return UNKNOWN_RECORD;
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}
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/* Checksum is initially 0.
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* For each data byte, XOR with the current checksum.
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* Rotate checksum left, carrying bit 7 to bit 0.
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@@ -131,45 +65,134 @@ uint8_t northstarChecksum(const Bytes& bytes) {
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return checksum;
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}
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void NorthstarDecoder::decodeSectorRecord()
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class NorthstarDecoder : public AbstractDecoder
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{
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unsigned recordSize, payloadSize, headerSize;
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public:
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NorthstarDecoder(const DecoderProto& config):
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AbstractDecoder(config),
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_config(config.northstar())
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{}
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if (_sectorType == SECTOR_TYPE_MFM) {
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recordSize = NORTHSTAR_ENCODED_SECTOR_SIZE_DD;
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payloadSize = NORTHSTAR_PAYLOAD_SIZE_DD;
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headerSize = NORTHSTAR_HEADER_SIZE_DD;
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}
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else {
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recordSize = NORTHSTAR_ENCODED_SECTOR_SIZE_SD;
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payloadSize = NORTHSTAR_PAYLOAD_SIZE_SD;
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headerSize = NORTHSTAR_HEADER_SIZE_SD;
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/* Search for FM or MFM sector record */
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RecordType advanceToNextRecord()
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{
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nanoseconds_t now = _fmr->tell().ns();
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/* For all but the first sector, seek to the next sector pulse.
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* The first sector does not contain the sector pulse in the fluxmap.
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*/
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if (now != 0) {
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_fmr->seekToIndexMark();
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now = _fmr->tell().ns();
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}
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/* Discard a possible partial sector at the end of the track.
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* This partial sector could be mistaken for a conflicted sector, if
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* whatever data read happens to match the checksum of 0, which is
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* rare, but has been observed on some disks.
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*/
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if (now > (_fmr->getDuration() - 21e6)) {
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_fmr->seekToIndexMark();
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return(UNKNOWN_RECORD);
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}
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int msSinceIndex = std::round(now / 1e6);
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const FluxMatcher* matcher = nullptr;
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/* Note that the seekToPattern ignores the sector pulses, so if
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* a sector is not found for some reason, the seek will advance
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* past one or more sector pulses. For this reason, calculate
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* _hardSectorId after the sector header is found.
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*/
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_sector->clock = _fmr->seekToPattern(ANY_SECTOR_PATTERN, matcher);
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int sectorFoundTimeRaw = std::round((_fmr->tell().ns()) / 1e6);
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int sectorFoundTime;
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/* Round time to the nearest 20ms */
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if ((sectorFoundTimeRaw % 20) < 10) {
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sectorFoundTime = (sectorFoundTimeRaw / 20) * 20;
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}
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else {
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sectorFoundTime = ((sectorFoundTimeRaw + 20) / 20) * 20;
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}
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/* Calculate the sector ID based on time since the index */
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_hardSectorId = (sectorFoundTime / 20) % 10;
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// std::cout << fmt::format(
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// "Sector ID {}: hole at {}ms, sector start at {}ms",
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// _hardSectorId, msSinceIndex, sectorFoundTimeRaw) << std::endl;
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if (matcher == &MFM_PATTERN) {
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_sectorType = SECTOR_TYPE_MFM;
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readRawBits(48);
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return SECTOR_RECORD;
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}
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if (matcher == &FM_PATTERN) {
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_sectorType = SECTOR_TYPE_FM;
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readRawBits(48);
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return SECTOR_RECORD;
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}
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return UNKNOWN_RECORD;
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}
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auto rawbits = readRawBits(recordSize * 16);
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auto bytes = decodeFmMfm(rawbits).slice(0, recordSize);
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ByteReader br(bytes);
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uint8_t sync_char;
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void decodeSectorRecord()
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{
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unsigned recordSize, payloadSize, headerSize;
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_sector->logicalSide = _sector->physicalSide;
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_sector->logicalSector = _hardSectorId;
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_sector->logicalTrack = _sector->physicalTrack;
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if (_sectorType == SECTOR_TYPE_MFM) {
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recordSize = NORTHSTAR_ENCODED_SECTOR_SIZE_DD;
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payloadSize = NORTHSTAR_PAYLOAD_SIZE_DD;
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headerSize = NORTHSTAR_HEADER_SIZE_DD;
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}
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else {
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recordSize = NORTHSTAR_ENCODED_SECTOR_SIZE_SD;
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payloadSize = NORTHSTAR_PAYLOAD_SIZE_SD;
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headerSize = NORTHSTAR_HEADER_SIZE_SD;
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}
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sync_char = br.read_8(); /* Sync char: 0xFB */
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if (_sectorType == SECTOR_TYPE_MFM) {
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sync_char = br.read_8();/* MFM second Sync char, usually 0xFB */
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auto rawbits = readRawBits(recordSize * 16);
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auto bytes = decodeFmMfm(rawbits).slice(0, recordSize);
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ByteReader br(bytes);
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uint8_t sync_char;
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_sector->logicalSide = _sector->physicalSide;
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_sector->logicalSector = _hardSectorId;
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_sector->logicalTrack = _sector->physicalTrack;
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sync_char = br.read_8(); /* Sync char: 0xFB */
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if (_sectorType == SECTOR_TYPE_MFM) {
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sync_char = br.read_8();/* MFM second Sync char, usually 0xFB */
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}
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_sector->data = br.read(payloadSize);
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uint8_t wantChecksum = br.read_8();
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uint8_t gotChecksum = northstarChecksum(bytes.slice(headerSize, payloadSize));
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_sector->status = (wantChecksum == gotChecksum) ? Sector::OK : Sector::BAD_CHECKSUM;
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}
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_sector->data = br.read(payloadSize);
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std::set<unsigned> requiredSectors(Track& track) const
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{
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static std::set<unsigned> sectors = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
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return sectors;
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}
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uint8_t wantChecksum = br.read_8();
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uint8_t gotChecksum = northstarChecksum(bytes.slice(headerSize, payloadSize));
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private:
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const NorthstarDecoderProto& _config;
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uint8_t _sectorType = SECTOR_TYPE_MFM;
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uint8_t _hardSectorId;
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};
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_sector->status = (wantChecksum == gotChecksum) ? Sector::OK : Sector::BAD_CHECKSUM;
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std::unique_ptr<AbstractDecoder> createNorthstarDecoder(const DecoderProto& config)
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{
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return std::unique_ptr<AbstractDecoder>(new NorthstarDecoder(config));
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}
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std::set<unsigned> NorthstarDecoder::requiredSectors(Track& track) const
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{
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static std::set<unsigned> sectors = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
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return sectors;
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}
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