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102 lines
3.4 KiB
C++
102 lines
3.4 KiB
C++
#include "lib/core/globals.h"
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#include "lib/decoders/decoders.h"
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#include "lib/encoders/encoders.h"
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#include "arch/tids990/tids990.h"
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#include "lib/core/crc.h"
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#include "lib/data/fluxmap.h"
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#include "lib/data/fluxmapreader.h"
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#include "lib/data/fluxpattern.h"
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#include "lib/data/sector.h"
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#include <string.h>
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#include "fmt/format.h"
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/* The Texas Instruments DS990 uses MFM with a scheme similar to a simplified
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* version of the IBM record scheme (it's actually easier to parse than IBM).
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* There are 26 sectors per track, each holding a rather weird 288 bytes.
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*/
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/*
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* Sector record:
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* data: 0 1 0 1 0 1 0 1 .0 0 0 0 1 0 1 0 = 0x550a
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* mfm: 00 01 00 01 00 01 00 01.00 10 10 10 01 00 01 00 = 0x11112a44
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* special: 00 01 00 01 00 01 00 01.00 10 00 10 01 00 01 00 = 0x11112244
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* ^^
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* When shifted out of phase, the special 0xa1 byte becomes an illegal
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* encoding (you can't do 10 00). So this can't be spoofed by user data.
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*/
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const uint16_t SECTOR_ID = 0x550a;
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const FluxPattern SECTOR_RECORD_PATTERN(32, 0x11112244);
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/*
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* Data record:
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* data: 0 1 0 1 0 1 0 1 .0 0 0 0 1 0 1 1 = 0x550b
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* mfm: 00 01 00 01 00 01 00 01.00 10 10 10 01 00 01 01 = 0x11112a45
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* special: 00 01 00 01 00 01 00 01.00 10 00 10 01 00 01 01 = 0x11112245
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* ^^
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* When shifted out of phase, the special 0xa1 byte becomes an illegal
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* encoding (you can't do 10 00). So this can't be spoofed by user data.
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*/
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const uint16_t DATA_ID = 0x550b;
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const FluxPattern DATA_RECORD_PATTERN(32, 0x11112245);
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const FluxMatchers ANY_RECORD_PATTERN(
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{&SECTOR_RECORD_PATTERN, &DATA_RECORD_PATTERN});
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class Tids990Decoder : public Decoder
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{
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public:
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Tids990Decoder(const DecoderProto& config): Decoder(config) {}
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nanoseconds_t advanceToNextRecord() override
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{
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return seekToPattern(ANY_RECORD_PATTERN);
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}
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void decodeSectorRecord() override
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{
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auto bits = readRawBits(TIDS990_SECTOR_RECORD_SIZE * 16);
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auto bytes = decodeFmMfm(bits).slice(0, TIDS990_SECTOR_RECORD_SIZE);
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ByteReader br(bytes);
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if (br.read_be16() != SECTOR_ID)
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return;
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uint16_t gotChecksum =
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crc16(CCITT_POLY, bytes.slice(1, TIDS990_SECTOR_RECORD_SIZE - 3));
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_sector->logicalSide = br.read_8() >> 3;
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_sector->logicalTrack = br.read_8();
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br.read_8(); /* number of sectors per track */
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_sector->logicalSector = br.read_8();
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br.read_be16(); /* sector size */
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uint16_t wantChecksum = br.read_be16();
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if (wantChecksum == gotChecksum)
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_sector->status =
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Sector::DATA_MISSING; /* correct but unintuitive */
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}
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void decodeDataRecord() override
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{
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auto bits = readRawBits(TIDS990_DATA_RECORD_SIZE * 16);
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auto bytes = decodeFmMfm(bits).slice(0, TIDS990_DATA_RECORD_SIZE);
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ByteReader br(bytes);
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if (br.read_be16() != DATA_ID)
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return;
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uint16_t gotChecksum =
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crc16(CCITT_POLY, bytes.slice(1, TIDS990_DATA_RECORD_SIZE - 3));
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_sector->data = br.read(TIDS990_PAYLOAD_SIZE);
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uint16_t wantChecksum = br.read_be16();
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_sector->status =
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(wantChecksum == gotChecksum) ? Sector::OK : Sector::BAD_CHECKSUM;
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}
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};
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std::unique_ptr<Decoder> createTids990Decoder(const DecoderProto& config)
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{
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return std::unique_ptr<Decoder>(new Tids990Decoder(config));
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}
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