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76 lines
2.1 KiB
C++
76 lines
2.1 KiB
C++
#include "globals.h"
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#include "decoders/decoders.h"
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#include "mx/mx.h"
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#include "crc.h"
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#include "fluxmap.h"
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#include "decoders/fluxmapreader.h"
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#include "sector.h"
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#include "record.h"
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#include "track.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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* 1010 1010 1010 1010 1111 1111 1010 1111
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* a a a a f f a f
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*/
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const FluxPattern ID_PATTERN(32, 0xaaaaffaf);
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void MxDecoder::beginTrack()
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{
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_currentSector = -1;
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_clock = 0;
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}
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AbstractDecoder::RecordType MxDecoder::advanceToNextRecord()
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{
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if (_currentSector == -1)
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{
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/* First sector in the track: look for the sync marker. */
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const FluxMatcher* matcher = nullptr;
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_sector->clock = _clock = _fmr->seekToPattern(ID_PATTERN, matcher);
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readRawBits(32); /* skip the ID mark */
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_logicalTrack = decodeFmMfm(readRawBits(32)).reader().read_be16();
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}
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else if (_currentSector == 10)
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{
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/* That was the last sector on the disk. */
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return UNKNOWN_RECORD;
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}
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else
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{
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/* Otherwise we assume the clock from the first sector is still valid.
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* The decoder framwork will automatically stop when we hit the end of
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* the track. */
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_sector->clock = _clock;
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}
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_currentSector++;
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return SECTOR_RECORD;
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}
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void MxDecoder::decodeSectorRecord()
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{
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auto bits = readRawBits((SECTOR_SIZE+2)*16);
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auto bytes = decodeFmMfm(bits).slice(0, SECTOR_SIZE+2).swab();
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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_le16();
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uint16_t wantChecksum = br.read_le16();
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_sector->logicalTrack = _logicalTrack;
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_sector->logicalSide = _track->physicalSide;
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_sector->logicalSector = _currentSector;
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_sector->data = bytes.slice(0, SECTOR_SIZE);
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_sector->status = (gotChecksum == wantChecksum) ? Sector::OK : Sector::BAD_CHECKSUM;
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}
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