1 #include "globals.h"
2 #include "decoders/decoders.h"
3 #include "aeslanier.h"
4 #include "crc.h"
5 #include "fluxmap.h"
6 #include "decoders/fluxmapreader.h"
7 #include "sector.h"
8 #include "bytes.h"
9 #include "record.h"
10 #include "fmt/format.h"
11 #include <string.h>
12 
13 static const FluxPattern SECTOR_PATTERN(32, AESLANIER_RECORD_SEPARATOR);
14 
15 /* This is actually M2FM, rather than MFM, but it our MFM/FM decoder copes fine with it. */
16 
reverse_bits(const Bytes & input)17 static Bytes reverse_bits(const Bytes& input)
18 {
19     Bytes output;
20     ByteWriter bw(output);
21 
22     for (uint8_t b : input)
23         bw.write_8(reverse_bits(b));
24     return output;
25 }
26 
advanceToNextRecord()27 AbstractDecoder::RecordType AesLanierDecoder::advanceToNextRecord()
28 {
29     _sector->clock = _fmr->seekToPattern(SECTOR_PATTERN);
30     if (_fmr->eof() || !_sector->clock)
31         return UNKNOWN_RECORD;
32     return SECTOR_RECORD;
33 }
34 
decodeSectorRecord()35 void AesLanierDecoder::decodeSectorRecord()
36 {
37     /* Skip ID mark. */
38 
39     readRawBits(16);
40 
41     const auto& rawbits = readRawBits(AESLANIER_RECORD_SIZE*16);
42     const auto& bytes = decodeFmMfm(rawbits).slice(0, AESLANIER_RECORD_SIZE);
43     const auto& reversed = reverse_bits(bytes);
44 
45     _sector->logicalTrack = reversed[1];
46     _sector->logicalSide = 0;
47     _sector->logicalSector = reversed[2];
48 
49     /* Check header 'checksum' (which seems far too simple to mean much). */
50 
51     {
52         uint8_t wanted = reversed[3];
53         uint8_t got = reversed[1] + reversed[2];
54         if (wanted != got)
55             return;
56     }
57 
58     /* Check data checksum, which also includes the header and is
59         * significantly better. */
60 
61     _sector->data = reversed.slice(1, AESLANIER_SECTOR_LENGTH);
62     uint16_t wanted = reversed.reader().seek(0x101).read_le16();
63     uint16_t got = crc16ref(MODBUS_POLY_REF, _sector->data);
64     _sector->status = (wanted == got) ? Sector::OK : Sector::BAD_CHECKSUM;
65 }
66