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Convert the Apple2 decoder.

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This commit is contained in:
David Given
2021-07-11 12:57:41 +02:00
parent 92aa28cac2
commit ce463686dc
3 changed files with 58 additions and 60 deletions
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15
arch/apple2/apple2.h
View File

@@ -7,21 +7,6 @@
#define APPLE2_SECTOR_LENGTH 256
#define APPLE2_ENCODED_SECTOR_LENGTH 342
class Sector;
class Fluxmap;
class Apple2DecoderProto;
class Apple2Decoder : public AbstractDecoder
{
public:
Apple2Decoder(const Apple2DecoderProto&) {}
virtual ~Apple2Decoder() {}
RecordType advanceToNextRecord();
void decodeSectorRecord();
void decodeDataRecord();
};
extern std::unique_ptr<AbstractDecoder> createApple2Decoder(const DecoderProto& config);
#endif

99
arch/apple2/decoder.cc
View File

@@ -60,53 +60,68 @@ static Bytes decode_crazy_data(const uint8_t* inp, Sector::Status& status)
return output;
}
uint8_t combine(uint16_t word)
static uint8_t combine(uint16_t word)
{
return word & (word >> 7);
}
AbstractDecoder::RecordType Apple2Decoder::advanceToNextRecord()
class Apple2Decoder : public AbstractDecoder
{
const FluxMatcher* matcher = nullptr;
_sector->clock = _fmr->seekToPattern(ANY_RECORD_PATTERN, matcher);
if (matcher == &SECTOR_RECORD_PATTERN)
return RecordType::SECTOR_RECORD;
if (matcher == &DATA_RECORD_PATTERN)
return RecordType::DATA_RECORD;
return RecordType::UNKNOWN_RECORD;
public:
Apple2Decoder(const DecoderProto& config):
AbstractDecoder(config)
{}
RecordType advanceToNextRecord()
{
const FluxMatcher* matcher = nullptr;
_sector->clock = _fmr->seekToPattern(ANY_RECORD_PATTERN, matcher);
if (matcher == &SECTOR_RECORD_PATTERN)
return RecordType::SECTOR_RECORD;
if (matcher == &DATA_RECORD_PATTERN)
return RecordType::DATA_RECORD;
return RecordType::UNKNOWN_RECORD;
}
void decodeSectorRecord()
{
/* Skip ID (as we know it's a APPLE2_SECTOR_RECORD). */
readRawBits(24);
/* Read header. */
auto header = toBytes(readRawBits(8*8)).slice(0, 8);
ByteReader br(header);
uint8_t volume = combine(br.read_be16());
_sector->logicalTrack = combine(br.read_be16());
_sector->logicalSector = combine(br.read_be16());
uint8_t checksum = combine(br.read_be16());
if (checksum == (volume ^ _sector->logicalTrack ^ _sector->logicalSector))
_sector->status = Sector::DATA_MISSING; /* unintuitive but correct */
}
void decodeDataRecord()
{
/* Check ID. */
Bytes bytes = toBytes(readRawBits(3*8)).slice(0, 3);
if (bytes.reader().read_be24() != APPLE2_DATA_RECORD)
return;
/* Read and decode data. */
unsigned recordLength = APPLE2_ENCODED_SECTOR_LENGTH + 2;
bytes = toBytes(readRawBits(recordLength*8)).slice(0, recordLength);
_sector->status = Sector::BAD_CHECKSUM;
_sector->data = decode_crazy_data(&bytes[0], _sector->status);
}
};
std::unique_ptr<AbstractDecoder> createApple2Decoder(const DecoderProto& config)
{
return std::unique_ptr<AbstractDecoder>(new Apple2Decoder(config));
}
void Apple2Decoder::decodeSectorRecord()
{
/* Skip ID (as we know it's a APPLE2_SECTOR_RECORD). */
readRawBits(24);
/* Read header. */
auto header = toBytes(readRawBits(8*8)).slice(0, 8);
ByteReader br(header);
uint8_t volume = combine(br.read_be16());
_sector->logicalTrack = combine(br.read_be16());
_sector->logicalSector = combine(br.read_be16());
uint8_t checksum = combine(br.read_be16());
if (checksum == (volume ^ _sector->logicalTrack ^ _sector->logicalSector))
_sector->status = Sector::DATA_MISSING; /* unintuitive but correct */
}
void Apple2Decoder::decodeDataRecord()
{
/* Check ID. */
Bytes bytes = toBytes(readRawBits(3*8)).slice(0, 3);
if (bytes.reader().read_be24() != APPLE2_DATA_RECORD)
return;
/* Read and decode data. */
unsigned recordLength = APPLE2_ENCODED_SECTOR_LENGTH + 2;
bytes = toBytes(readRawBits(recordLength*8)).slice(0, recordLength);
_sector->status = Sector::BAD_CHECKSUM;
_sector->data = decode_crazy_data(&bytes[0], _sector->status);
}

4
lib/decoders/decoders.cc
View File

@@ -34,6 +34,7 @@ std::unique_ptr<AbstractDecoder> AbstractDecoder::create(const DecoderProto& con
{
{ DecoderProto::kAeslanier, createAesLanierDecoder },
{ DecoderProto::kAmiga, createAmigaDecoder },
{ DecoderProto::kApple2, createApple2Decoder },
};
auto decoder = decoders.find(config.format_case());
@@ -48,9 +49,6 @@ std::unique_ptr<AbstractDecoder> AbstractDecoder::create(const DecoderProto& con
{
switch (config.format_case())
{
case DecoderProto::kAeslanier:
return std::unique_ptr<AbstractDecoder>(new AesLanierDecoder(config.aeslanier()));
case DecoderProto::kApple2:
return std::unique_ptr<AbstractDecoder>(new Apple2Decoder(config.apple2()));