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57 lines
1.5 KiB
C++
57 lines
1.5 KiB
C++
#include "globals.h"
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#include "fluxmap.h"
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#include "decoders/fluxmapreader.h"
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#include "decoders/decoders.h"
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#include "sector.h"
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#include "micropolis.h"
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#include "bytes.h"
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#include "fmt/format.h"
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/* The sector has a preamble of MFM 0x00s and uses 0xFF as a sync pattern. */
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static const FluxPattern SECTOR_SYNC_PATTERN(32, 0xaaaa5555);
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AbstractDecoder::RecordType MicropolisDecoder::advanceToNextRecord()
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{
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_fmr->seekToIndexMark();
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const FluxMatcher* matcher = nullptr;
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_sector->clock = _fmr->seekToPattern(SECTOR_SYNC_PATTERN, matcher);
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if (matcher == &SECTOR_SYNC_PATTERN) {
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readRawBits(16);
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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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static uint8_t checksum(const Bytes& bytes) {
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ByteReader br(bytes);
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uint16_t sum = 0;
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while (!br.eof()) {
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sum += br.read_8();
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}
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return (sum & 0xFF) + (sum >> 8);
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}
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void MicropolisDecoder::decodeSectorRecord()
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{
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auto rawbits = readRawBits(MICROPOLIS_ENCODED_SECTOR_SIZE*16);
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auto bytes = decodeFmMfm(rawbits).slice(0, MICROPOLIS_ENCODED_SECTOR_SIZE);
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ByteReader br(bytes);
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br.read_8(); /* sync */
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_sector->logicalTrack = br.read_8();
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_sector->logicalSide = _sector->physicalSide;
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_sector->logicalSector = br.read_8();
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if (_sector->logicalSector > 15)
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return;
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if (_sector->logicalTrack > 77)
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return;
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br.read(10); /* OS data or padding */
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_sector->data = br.read(256);
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uint8_t wantChecksum = br.read_8();
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uint8_t gotChecksum = checksum(bytes.slice(1, 2+266));
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br.read(5); /* 4 byte ECC and ECC-present flag */
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_sector->status = (wantChecksum == gotChecksum) ? Sector::OK : Sector::BAD_CHECKSUM;
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}
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