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Finally make the Amiga encoder work properly. Do some FM/MFM/bits refactoring.

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This commit is contained in:
David Given
2021-07-05 23:16:03 +02:00
parent ec689e100e
commit 56cbf39d59
5 changed files with 93 additions and 27 deletions
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62
arch/amiga/encoder.cc
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@@ -22,13 +22,14 @@ static void write_bits(std::vector<bool>& bits, unsigned& cursor, const std::vec
for (bool bit : src)
{
if (cursor < bits.size())
bits[cursor++] = bit;
lastBit = bits[cursor++] = bit;
}
}
static void write_bits(std::vector<bool>& bits, unsigned& cursor, uint64_t data, int width)
{
cursor += width;
lastBit = data & 1;
for (int i=0; i<width; i++)
{
unsigned pos = cursor - i - 1;
@@ -38,19 +39,16 @@ static void write_bits(std::vector<bool>& bits, unsigned& cursor, uint64_t data,
}
}
static void write_interleaved_bytes(std::vector<bool>& bits, unsigned& cursor, const Bytes& bytes)
static void write_bits(std::vector<bool>& bits, unsigned& cursor, const Bytes& bytes)
{
assert(!(bytes.size() & 3));
Bytes interleaved = amigaInterleave(bytes);
encodeMfm(bits, cursor, interleaved, lastBit);
}
ByteReader br(bytes);
BitReader bitr(br);
static void write_interleaved_bytes(std::vector<bool>& bits, unsigned& cursor, uint32_t data)
{
Bytes b(4);
ByteWriter bw(b);
bw.write_be32(data);
write_interleaved_bytes(bits, cursor, b);
while (!bitr.eof())
{
if (cursor < bits.size())
bits[cursor++] = bitr.get();
}
}
static void write_sector(std::vector<bool>& bits, unsigned& cursor, const Sector* sector)
@@ -58,11 +56,27 @@ static void write_sector(std::vector<bool>& bits, unsigned& cursor, const Sector
if ((sector->data.size() != 512) && (sector->data.size() != 528))
Error() << "unsupported sector size --- you must pick 512 or 528";
uint32_t checksum = 0;
auto write_interleaved_bytes = [&](const Bytes& bytes)
{
Bytes interleaved = amigaInterleave(bytes);
Bytes mfm = encodeMfm(interleaved, lastBit);
checksum ^= amigaChecksum(mfm);
checksum &= 0x55555555;
write_bits(bits, cursor, mfm);
};
auto write_interleaved_word = [&](uint32_t word)
{
Bytes b(4);
b.writer().write_be32(word);
write_interleaved_bytes(b);
};
write_bits(bits, cursor, AMIGA_SECTOR_RECORD, 6*8);
std::vector<bool> headerBits(20*16);
unsigned headerCursor = 0;
checksum = 0;
Bytes header =
{
0xff, /* Amiga 1.0 format byte */
@@ -70,22 +84,16 @@ static void write_sector(std::vector<bool>& bits, unsigned& cursor, const Sector
(uint8_t) sector->logicalSector,
(uint8_t) (AMIGA_SECTORS_PER_TRACK - sector->logicalSector)
};
write_interleaved_bytes(headerBits, headerCursor, header);
write_interleaved_bytes(header);
Bytes recoveryInfo(16);
if (sector->data.size() == 528)
recoveryInfo = sector->data.slice(512, 16);
write_interleaved_bytes(headerBits, headerCursor, recoveryInfo);
write_interleaved_bytes(recoveryInfo);
write_interleaved_word(checksum);
std::vector<bool> dataBits(512*16);
unsigned dataCursor = 0;
write_interleaved_bytes(dataBits, dataCursor, sector->data);
write_bits(bits, cursor, headerBits);
uint32_t headerChecksum = amigaChecksum(toBytes(headerBits));
write_interleaved_bytes(bits, cursor, headerChecksum);
uint32_t dataChecksum = amigaChecksum(toBytes(dataBits));
write_interleaved_bytes(bits, cursor, dataChecksum);
write_bits(bits, cursor, dataBits);
Bytes data = sector->data.slice(0, 512);
write_interleaved_word(amigaChecksum(encodeMfm(amigaInterleave(data), lastBit)));
write_interleaved_bytes(data);
}
std::unique_ptr<Fluxmap> AmigaEncoder::encode(