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84 lines
2.3 KiB
C++
84 lines
2.3 KiB
C++
#include "lib/globals.h"
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#include "lib/decoders/decoders.h"
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#include "arch/mx/mx.h"
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#include "lib/crc.h"
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#include "lib/fluxmap.h"
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#include "lib/decoders/fluxmapreader.h"
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#include "lib/sector.h"
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#include <string.h>
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const int SECTOR_SIZE = 256;
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/*
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* MX disks are a bunch of sectors glued together with no gaps or sync markers,
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* following a single beginning-of-track synchronisation and identification
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* sequence.
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*/
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/* FM beginning of track marker:
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* 0 0 f 3 decoded nibbles
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* 0 0 0 0 0 0 0 0 1 1 1 1 0 0 1 1
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* 1010 1010 1010 1010 1111 1111 1010 1111
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* a a a a f f a f encoded nibbles
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*/
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const FluxPattern ID_PATTERN(32, 0xaaaaffaf);
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class MxDecoder : public Decoder
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{
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public:
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MxDecoder(const DecoderProto& config): Decoder(config) {}
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void beginTrack() override
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{
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_clock = _sector->clock = seekToPattern(ID_PATTERN);
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_currentSector = 0;
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}
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nanoseconds_t advanceToNextRecord() override
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{
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if (_currentSector == 11)
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{
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/* That was the last sector on the disk. */
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return 0;
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}
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else
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return _clock;
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}
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void decodeSectorRecord() override
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{
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/* Skip the ID pattern and track word, which is only present on the
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* first sector. We don't trust the track word because some driver
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* don't write it correctly. */
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if (_currentSector == 0)
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readRawBits(64);
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auto bits = readRawBits((SECTOR_SIZE + 2) * 16);
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auto bytes = decodeFmMfm(bits).slice(0, SECTOR_SIZE + 2);
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uint16_t gotChecksum = 0;
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ByteReader br(bytes);
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for (int i = 0; i < (SECTOR_SIZE / 2); i++)
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gotChecksum += br.read_be16();
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uint16_t wantChecksum = br.read_be16();
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_sector->logicalTrack = _sector->physicalTrack;
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_sector->logicalSide = _sector->physicalSide;
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_sector->logicalSector = _currentSector;
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_sector->data = bytes.slice(0, SECTOR_SIZE).swab();
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_sector->status =
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(gotChecksum == wantChecksum) ? Sector::OK : Sector::BAD_CHECKSUM;
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_currentSector++;
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}
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private:
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nanoseconds_t _clock;
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int _currentSector;
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};
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std::unique_ptr<Decoder> createMxDecoder(const DecoderProto& config)
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{
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return std::unique_ptr<Decoder>(new MxDecoder(config));
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}
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