Path: blob/master/BizHawk.Emulation.Cores/Computers/Commodore64/Media/D64.cs
2 views
using System;
using System.Collections.Generic;
using System.IO;
namespace BizHawk.Emulation.Cores.Computers.Commodore64.Media
{
public static class D64
{
private static readonly int[] DensityTable =
{
3, 3, 3, 3, 3,
3, 3, 3, 3, 3,
3, 3, 3, 3, 3,
3, 3, 2, 2, 2,
2, 2, 2, 2, 1,
1, 1, 1, 1, 1,
0, 0, 0, 0, 0,
0, 0, 0, 0, 0
};
private static readonly int[] GcrDecodeTable =
{
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, //00xxx
0xFF, 0x08, 0x00, 0x01, 0xFF, 0x0C, 0x04, 0x05, //01xxx
0xFF, 0xFF, 0x02, 0x03, 0xFF, 0x0F, 0x06, 0x07, //10xxx
0xFF, 0x09, 0x0A, 0x0B, 0xFF, 0x0D, 0x0E, 0xFF //11xxx
};
private static readonly int[] GcrEncodeTable =
{
Convert.ToByte("01010", 2), // 0
Convert.ToByte("01011", 2), // 1
Convert.ToByte("10010", 2), // 2
Convert.ToByte("10011", 2), // 3
Convert.ToByte("01110", 2), // 4
Convert.ToByte("01111", 2), // 5
Convert.ToByte("10110", 2), // 6
Convert.ToByte("10111", 2), // 7
Convert.ToByte("01001", 2), // 8
Convert.ToByte("11001", 2), // 9
Convert.ToByte("11010", 2), // A
Convert.ToByte("11011", 2), // B
Convert.ToByte("01101", 2), // C
Convert.ToByte("11101", 2), // D
Convert.ToByte("11110", 2), // E
Convert.ToByte("10101", 2) // F
};
private static readonly int[] SectorsPerTrack =
{
21, 21, 21, 21, 21,
21, 21, 21, 21, 21,
21, 21, 21, 21, 21,
21, 21, 19, 19, 19,
19, 19, 19, 19, 18,
18, 18, 18, 18, 18,
17, 17, 17, 17, 17,
17, 17, 17, 17, 17
};
private static readonly int[] StandardTrackLengthBytes =
{
6250, 6666, 7142, 7692
};
private static byte Checksum(byte[] source)
{
var count = source.Length;
byte result = 0;
for (var i = 0; i < count; i++)
result ^= source[i];
return result;
}
private static byte[] ConvertSectorToGcr(byte[] source, byte sectorNo, byte trackNo, byte formatA, byte formatB, out int bitsWritten)
{
using (var mem = new MemoryStream())
{
var writer = new BinaryWriter(mem);
var headerChecksum = (byte)(sectorNo ^ trackNo ^ formatA ^ formatB);
// assemble written data for GCR encoding
var writtenData = new byte[260];
Array.Copy(source, 0, writtenData, 1, 256);
writtenData[0] = 0x07;
writtenData[0x101] = Checksum(source);
writtenData[0x102] = 0x00;
writtenData[0x103] = 0x00;
writer.Write(new byte[] { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF }); // sync
writer.Write(EncodeGcr(new byte[] { 0x08, headerChecksum, sectorNo, trackNo, formatA, formatB, 0x0F, 0x0F })); // header
writer.Write(new byte[] { 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55 }); // gap
writer.Write(new byte[] { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF }); // sync
writer.Write(EncodeGcr(writtenData)); // data
writer.Write(new byte[] { 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55 }); // gap
bitsWritten = (int)mem.Length * 8;
writer.Flush();
return mem.ToArray();
}
}
private static byte[] EncodeGcr(byte[] source)
{
// 4 bytes -> 5 GCR encoded bytes
var gcr = new int[8];
var data = new byte[4];
var count = source.Length;
using (var mem = new MemoryStream())
{
var writer = new BinaryWriter(mem);
for (var i = 0; i < count; i += 4)
{
Array.Copy(source, i, data, 0, 4);
gcr[0] = GcrEncodeTable[data[0] >> 4];
gcr[1] = GcrEncodeTable[data[0] & 0xF];
gcr[2] = GcrEncodeTable[data[1] >> 4];
gcr[3] = GcrEncodeTable[data[1] & 0xF];
gcr[4] = GcrEncodeTable[data[2] >> 4];
gcr[5] = GcrEncodeTable[data[2] & 0xF];
gcr[6] = GcrEncodeTable[data[3] >> 4];
gcr[7] = GcrEncodeTable[data[3] & 0xF];
// -------- -------- -------- -------- --------
// 00000111 11222223 33334444 45555566 66677777
var outputValue = (gcr[0] << 3) | (gcr[1] >> 2);
writer.Write((byte)(outputValue & 0xFF));
outputValue = (gcr[1] << 6) | (gcr[2] << 1) | (gcr[3] >> 4);
writer.Write((byte)(outputValue & 0xFF));
outputValue = (gcr[3] << 4) | (gcr[4] >> 1);
writer.Write((byte)(outputValue & 0xFF));
outputValue = (gcr[4] << 7) | (gcr[5] << 2) | (gcr[6] >> 3);
writer.Write((byte)(outputValue & 0xFF));
outputValue = (gcr[6] << 5) | (gcr[7]);
writer.Write((byte)(outputValue & 0xFF));
}
writer.Flush();
return mem.ToArray();
}
}
public static Disk Read(byte[] source)
{
using (var mem = new MemoryStream(source))
{
var reader = new BinaryReader(mem);
var trackDatas = new List<byte[]>();
var trackLengths = new List<int>();
var trackNumbers = new List<int>();
var trackDensities = new List<int>();
int trackCount;
switch (source.Length)
{
case 174848: // 35 tracks no errors
trackCount = 35;
break;
case 175531: // 35 tracks with errors
trackCount = 35;
break;
case 196608: // 40 tracks no errors
trackCount = 40;
break;
case 197376: // 40 tracks with errors
trackCount = 40;
break;
default:
throw new Exception("Not able to identify capacity of the D64 file.");
}
for (var i = 0; i < trackCount; i++)
{
var sectors = SectorsPerTrack[i];
var trackLengthBits = 0;
using (var trackMem = new MemoryStream())
{
for (var j = 0; j < sectors; j++)
{
int bitsWritten;
var sectorData = reader.ReadBytes(256);
var diskData = ConvertSectorToGcr(sectorData, (byte)j, (byte)(i + 1), 0xA0, 0xA0, out bitsWritten);
trackMem.Write(diskData, 0, diskData.Length);
trackLengthBits += bitsWritten;
}
var density = DensityTable[i];
// we pad the tracks with extra gap bytes to meet MNIB standards
while (trackMem.Length < StandardTrackLengthBytes[density])
{
trackMem.WriteByte(0x55);
}
trackDatas.Add(trackMem.ToArray());
trackLengths.Add(trackLengthBits);
trackNumbers.Add(i * 2);
trackDensities.Add(DensityTable[i]);
}
}
return new Disk(trackDatas, trackNumbers, trackDensities, 84);
}
}
}
}