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Add some helper methods to make decoders easier. Port IBM to the new new

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architecture.
This commit is contained in:
David Given
2019-04-30 20:45:16 +02:00
parent 4cc680057e
commit 184e7766f0
5 changed files with 137 additions and 138 deletions
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84
lib/ibm/decoder.cc
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@@ -76,7 +76,7 @@ const FluxPattern FM_TRS80DAM2_PATTERN(16, 0xf56c);
*/
const FluxPattern MFM_PATTERN(16, 0x4489);
const FluxMatchers SEPARATOR_PATTERNS(
const FluxMatchers ANY_RECORD_PATTERN(
{
&MFM_PATTERN,
&FM_IDAM_PATTERN,
@@ -87,77 +87,67 @@ const FluxMatchers SEPARATOR_PATTERNS(
}
);
nanoseconds_t IbmDecoder::findSector(FluxmapReader& fmr, Track& track)
AbstractSimplifiedDecoder::RecordType IbmDecoder::advanceToNextRecord()
{
for (;;)
const FluxMatcher* matcher = nullptr;
_sector->clock = _fmr->seekToPattern(ANY_RECORD_PATTERN, matcher);
/* If this is the MFM prefix byte, the the decoder is going to expect three
* extra bytes on the front of the header. */
_currentHeaderLength = (matcher == &MFM_PATTERN) ? 3 : 0;
Fluxmap::Position here = tell();
if (_currentHeaderLength > 0)
readRawBits(_currentHeaderLength*16);
auto idbits = readRawBits(16);
uint8_t id = decodeFmMfm(idbits).slice(0, 1)[0];
seek(here);
switch (id)
{
nanoseconds_t clock = fmr.seekToPattern(SEPARATOR_PATTERNS);
if (fmr.eof() || !clock)
return 0;
case IBM_IDAM:
return RecordType::SECTOR_RECORD;
auto here = fmr.tell();
auto idbits = fmr.readRawBits(16, clock);
uint8_t id = decodeFmMfm(idbits).slice(0, 1)[0];
fmr.seek(here);
/* If this is the MFM prefix byte, the the decoder is going to expect three
* extra bytes on the front of the header. */
_currentHeaderLength = (id == IBM_MFM_SYNC) ? 3 : 0;
switch (id)
{
case IBM_MFM_SYNC:
case IBM_IDAM:
case IBM_DAM1:
case IBM_DAM2:
case IBM_TRS80DAM1:
case IBM_TRS80DAM2:
return clock;
}
fmr.readRawBit(clock);
case IBM_DAM1:
case IBM_DAM2:
case IBM_TRS80DAM1:
case IBM_TRS80DAM2:
return RecordType::DATA_RECORD;
}
return RecordType::UNKNOWN_RECORD;
}
nanoseconds_t IbmDecoder::findData(FluxmapReader& fmr, Track& track)
{
return findSector(fmr, track);
}
void IbmDecoder::decodeHeader(FluxmapReader& fmr, Track& track, Sector& sector)
void IbmDecoder::decodeSectorRecord()
{
unsigned recordSize = _currentHeaderLength + IBM_IDAM_LEN;
auto bits = fmr.readRawBits(recordSize*16, sector.clock);
auto bits = readRawBits(recordSize*16);
auto bytes = decodeFmMfm(bits).slice(0, recordSize);
ByteReader br(bytes);
br.seek(_currentHeaderLength);
uint8_t id = br.read_8();
if (id != IBM_IDAM)
return;
sector.logicalTrack = br.read_8();
sector.logicalSide = br.read_8();
sector.logicalSector = br.read_8() - _sectorBase;
br.read_8(); /* skip ID byte */
_sector->logicalTrack = br.read_8();
_sector->logicalSide = br.read_8();
_sector->logicalSector = br.read_8() - _sectorBase;
_currentSectorSize = 1 << (br.read_8() + 7);
uint16_t wantCrc = br.read_be16();
uint16_t gotCrc = crc16(CCITT_POLY, bytes.slice(0, _currentHeaderLength + 5));
if (wantCrc == gotCrc)
sector.status = Sector::DATA_MISSING; /* correct but unintuitive */
_sector->status = Sector::DATA_MISSING; /* correct but unintuitive */
}
void IbmDecoder::decodeData(FluxmapReader& fmr, Track& track, Sector& sector)
void IbmDecoder::decodeDataRecord()
{
unsigned recordLength = _currentHeaderLength + _currentSectorSize + 3;
auto bits = fmr.readRawBits(recordLength*16, sector.clock);
auto bits = readRawBits(recordLength*16);
auto bytes = decodeFmMfm(bits).slice(0, recordLength);
ByteReader br(bytes);
br.seek(_currentHeaderLength);
uint8_t id = br.read_8();
if ((id != IBM_DAM1) && (id != IBM_DAM2) && (id != IBM_TRS80DAM1) && (id != IBM_TRS80DAM2))
return;
br.read_8(); /* skip ID byte */
sector.data = br.read(_currentSectorSize);
_sector->data = br.read(_currentSectorSize);
uint16_t wantCrc = br.read_be16();
uint16_t gotCrc = crc16(CCITT_POLY, bytes.slice(0, recordLength-2));
sector.status = (wantCrc == gotCrc) ? Sector::OK : Sector::BAD_CHECKSUM;
_sector->status = (wantCrc == gotCrc) ? Sector::OK : Sector::BAD_CHECKSUM;
}