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Convert the IBM decoder.

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This commit is contained in:
David Given
2021-07-11 15:56:20 +02:00
parent dd951dc0ed
commit 25ebad2448
3 changed files with 91 additions and 87 deletions
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158
arch/ibm/decoder.cc
View File

@@ -91,76 +91,98 @@ const FluxMatchers ANY_RECORD_PATTERN(
}
);
std::set<unsigned> IbmDecoder::requiredSectors(Track& track) const
class IbmDecoder : public AbstractDecoder
{
return iterate(_config.required_sectors());
public:
IbmDecoder(const DecoderProto& config):
AbstractDecoder(config),
_config(config.ibm())
{}
RecordType advanceToNextRecord()
{
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);
const Bytes idbytes = decodeFmMfm(idbits);
uint8_t id = idbytes.slice(0, 1)[0];
seek(here);
switch (id)
{
case IBM_IDAM:
return RecordType::SECTOR_RECORD;
case IBM_DAM1:
case IBM_DAM2:
case IBM_TRS80DAM1:
case IBM_TRS80DAM2:
return RecordType::DATA_RECORD;
}
return RecordType::UNKNOWN_RECORD;
}
void decodeSectorRecord()
{
unsigned recordSize = _currentHeaderLength + IBM_IDAM_LEN;
auto bits = readRawBits(recordSize*16);
auto bytes = decodeFmMfm(bits).slice(0, recordSize);
ByteReader br(bytes);
br.seek(_currentHeaderLength);
br.read_8(); /* skip ID byte */
_sector->logicalTrack = br.read_8();
_sector->logicalSide = br.read_8();
_sector->logicalSector = br.read_8() - _config.sector_id_base();
_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 */
if (_config.ignore_side_byte())
_sector->logicalSide = _sector->physicalSide;
}
void decodeDataRecord()
{
unsigned recordLength = _currentHeaderLength + _currentSectorSize + 3;
auto bits = readRawBits(recordLength*16);
auto bytes = decodeFmMfm(bits).slice(0, recordLength);
ByteReader br(bytes);
br.seek(_currentHeaderLength);
br.read_8(); /* skip ID byte */
_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;
}
std::set<unsigned> requiredSectors(Track& track) const
{
return iterate(_config.required_sectors());
}
private:
const IbmDecoderProto& _config;
unsigned _currentSectorSize;
unsigned _currentHeaderLength;
};
std::unique_ptr<AbstractDecoder> createIbmDecoder(const DecoderProto& config)
{
return std::unique_ptr<AbstractDecoder>(new IbmDecoder(config));
}
AbstractDecoder::RecordType IbmDecoder::advanceToNextRecord()
{
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);
const Bytes idbytes = decodeFmMfm(idbits);
uint8_t id = idbytes.slice(0, 1)[0];
seek(here);
switch (id)
{
case IBM_IDAM:
return RecordType::SECTOR_RECORD;
case IBM_DAM1:
case IBM_DAM2:
case IBM_TRS80DAM1:
case IBM_TRS80DAM2:
return RecordType::DATA_RECORD;
}
return RecordType::UNKNOWN_RECORD;
}
void IbmDecoder::decodeSectorRecord()
{
unsigned recordSize = _currentHeaderLength + IBM_IDAM_LEN;
auto bits = readRawBits(recordSize*16);
auto bytes = decodeFmMfm(bits).slice(0, recordSize);
ByteReader br(bytes);
br.seek(_currentHeaderLength);
br.read_8(); /* skip ID byte */
_sector->logicalTrack = br.read_8();
_sector->logicalSide = br.read_8();
_sector->logicalSector = br.read_8() - _config.sector_id_base();
_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 */
if (_config.ignore_side_byte())
_sector->logicalSide = _sector->physicalSide;
}
void IbmDecoder::decodeDataRecord()
{
unsigned recordLength = _currentHeaderLength + _currentSectorSize + 3;
auto bits = readRawBits(recordLength*16);
auto bytes = decodeFmMfm(bits).slice(0, recordLength);
ByteReader br(bytes);
br.seek(_currentHeaderLength);
br.read_8(); /* skip ID byte */
_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;
}

19
arch/ibm/ibm.h
View File

@@ -30,25 +30,6 @@ struct IbmIdam
uint8_t crc[2];
};
class IbmDecoder : public AbstractDecoder
{
public:
IbmDecoder(const IbmDecoderProto& config):
_config(config)
{}
RecordType advanceToNextRecord();
void decodeSectorRecord();
void decodeDataRecord();
std::set<unsigned> requiredSectors(Track& track) const;
private:
const IbmDecoderProto& _config;
unsigned _currentSectorSize;
unsigned _currentHeaderLength;
};
class IbmEncoder : public AbstractEncoder
{
public:

1
lib/decoders/decoders.cc
View File

@@ -40,6 +40,7 @@ std::unique_ptr<AbstractDecoder> AbstractDecoder::create(const DecoderProto& con
{ DecoderProto::kC64, createCommodore64Decoder },
{ DecoderProto::kF85, createDurangoF85Decoder },
{ DecoderProto::kFb100, createFb100Decoder },
{ DecoderProto::kIbm, createIbmDecoder },
};
auto decoder = decoders.find(config.format_case());