BizHawk/BizHawk.Emulation.Cores/Computers/AmstradCPC/Media/Disk/CPCExtendedFloppyDisk.cs

using System.Text;
using BizHawk.Common;
using System;
using System.Collections.Generic;

namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
{
	/// <summary>
	/// Logical object representing a standard +3 disk image
	/// </summary>
	public class CPCExtendedFloppyDisk : FloppyDisk
	{
		/// <summary>
		/// The format type
		/// </summary>
		public override DiskType DiskFormatType => DiskType.CPCExtended;

		/// <summary>
		/// Attempts to parse incoming disk data
		/// </summary>
		/// <returns>
		/// TRUE:   disk parsed
		/// FALSE:  unable to parse disk
		/// </returns>
		public override bool ParseDisk(byte[] data)
		{
			// look for standard magic string
			string ident = Encoding.ASCII.GetString(data, 0, 16);

			if (!ident.ToUpper().Contains("EXTENDED CPC DSK"))
			{
				// incorrect format
				return false;
			}

			// read the disk information block
			DiskHeader.DiskIdent = ident;
			DiskHeader.DiskCreatorString = Encoding.ASCII.GetString(data, 0x22, 14);
			DiskHeader.NumberOfTracks = data[0x30];
			DiskHeader.NumberOfSides = data[0x31];
			DiskHeader.TrackSizes = new int[DiskHeader.NumberOfTracks * DiskHeader.NumberOfSides];
			DiskTracks = new Track[DiskHeader.NumberOfTracks * DiskHeader.NumberOfSides];
			DiskData = data;
			int pos = 0x34;

			if (DiskHeader.NumberOfSides > 1)
			{
				StringBuilder sbm = new StringBuilder();
				sbm.AppendLine();
				sbm.AppendLine();
				sbm.AppendLine("The detected disk image contains multiple sides.");
				sbm.AppendLine("This is NOT currently supported in CPCHawk.");
				sbm.AppendLine("Please find an alternate image/dump where each side has been saved as a separate *.dsk image (and use the multi-disk bundler tool to load into Bizhawk).");
				throw new System.NotImplementedException(sbm.ToString());
			}

			for (int i = 0; i < DiskHeader.NumberOfTracks * DiskHeader.NumberOfSides; i++)
			{
				DiskHeader.TrackSizes[i] = data[pos++] * 256;
			}

			// move to first track information block
			pos = 0x100;

			// parse each track
			for (int i = 0; i < DiskHeader.NumberOfTracks * DiskHeader.NumberOfSides; i++)
			{
				// check for unformatted track
				if (DiskHeader.TrackSizes[i] == 0)
				{
					DiskTracks[i] = new Track { Sectors = new Sector[0] };
					continue;
				}

				int p = pos;
				DiskTracks[i] = new Track();

				// track info block
				DiskTracks[i].TrackIdent = Encoding.ASCII.GetString(data, p, 12);
				p += 16;
				DiskTracks[i].TrackNumber = data[p++];
				DiskTracks[i].SideNumber = data[p++];
				DiskTracks[i].DataRate = data[p++];
				DiskTracks[i].RecordingMode = data[p++];
				DiskTracks[i].SectorSize = data[p++];
				DiskTracks[i].NumberOfSectors = data[p++];
				DiskTracks[i].GAP3Length = data[p++];
				DiskTracks[i].FillerByte = data[p++];

				int dpos = pos + 0x100;

				// sector info list
				DiskTracks[i].Sectors = new Sector[DiskTracks[i].NumberOfSectors];
				for (int s = 0; s < DiskTracks[i].NumberOfSectors; s++)
				{
					DiskTracks[i].Sectors[s] = new Sector
					{
						TrackNumber = data[p++],
						SideNumber = data[p++],
						SectorID = data[p++],
						SectorSize = data[p++],
						Status1 = data[p++],
						Status2 = data[p++],
						ActualDataByteLength = MediaConverter.GetWordValue(data, p)
					};
					p += 2;

					// sector data - begins at 0x100 offset from the start of the track info block (in this case dpos)
					DiskTracks[i].Sectors[s].SectorData = new byte[DiskTracks[i].Sectors[s].ActualDataByteLength];

					// copy the data
					for (int b = 0; b < DiskTracks[i].Sectors[s].ActualDataByteLength; b++)
					{
						DiskTracks[i].Sectors[s].SectorData[b] = data[dpos + b];
					}

					// check for multiple weak/random sectors stored
					if (DiskTracks[i].Sectors[s].SectorSize <= 7)
					{
						// sectorsize n=8 is equivilent to n=0 - FDC will use DTL for length
						int specifiedSize = 0x80 << DiskTracks[i].Sectors[s].SectorSize;

						if (specifiedSize < DiskTracks[i].Sectors[s].ActualDataByteLength)
						{
							// more data stored than sectorsize defines
							// check for multiple weak/random copies
							if (DiskTracks[i].Sectors[s].ActualDataByteLength % specifiedSize != 0)
							{
								DiskTracks[i].Sectors[s].ContainsMultipleWeakSectors = true;
							}
						}
					}

					// move dpos to the next sector data postion
					dpos += DiskTracks[i].Sectors[s].ActualDataByteLength;
				}

				// move to the next track info block
				pos += DiskHeader.TrackSizes[i];
			}

			// run protection scheme detector
			ParseProtection();

			return true;
		}

		/// <summary>
		/// Takes a double-sided disk byte array and converts into 2 single-sided arrays
		/// </summary>
		public static bool SplitDoubleSided(byte[] data, List<byte[]> results)
		{
			// look for standard magic string
			string ident = Encoding.ASCII.GetString(data, 0, 16);
			if (!ident.ToUpper().Contains("EXTENDED CPC DSK"))
			{
				// incorrect format
				return false;
			}

			byte[] S0 = new byte[data.Length];
			byte[] S1 = new byte[data.Length];

			// disk info block
			Array.Copy(data, 0, S0, 0, 0x100);
			Array.Copy(data, 0, S1, 0, 0x100);
			// change side number
			S0[0x31] = 1;
			S1[0x31] = 1;

			// extended format has different track sizes
			int[] trkSizes = new int[data[0x30] * data[0x31]];

			int pos = 0x34;
			for (int i = 0; i < data[0x30] * data[0x31]; i++)
			{
				trkSizes[i] = data[pos] * 256;
				// clear destination trk sizes (will be added later)
				S0[pos] = 0;
				S1[pos] = 0;
				pos++;
			}

			// start at track info blocks
			int mPos = 0x100;
			int s0Pos = 0x100;
			int s0tCount = 0;
			int s1tCount = 0;
			int s1Pos = 0x100;
			int tCount = 0;

			while (tCount < data[0x30] * data[0x31])
			{
				// which side is this?
				var side = data[mPos + 0x11];
				if (side == 0)
				{
					// side 1
					Array.Copy(data, mPos, S0, s0Pos, trkSizes[tCount]);
					s0Pos += trkSizes[tCount];
					// trk size table
					S0[0x34 + s0tCount++] = (byte)(trkSizes[tCount] / 256);
				}
				else if (side == 1)
				{
					// side 2
					Array.Copy(data, mPos, S1, s1Pos, trkSizes[tCount]);
					s1Pos += trkSizes[tCount];
					// trk size table
					S1[0x34 + s1tCount++] = (byte)(trkSizes[tCount] / 256);
				}

				mPos += trkSizes[tCount++];
			}

			byte[] s0final = new byte[s0Pos];
			byte[] s1final = new byte[s1Pos];
			Array.Copy(S0, 0, s0final, 0, s0Pos);
			Array.Copy(S1, 0, s1final, 0, s1Pos);

			results.Add(s0final);
			results.Add(s1final);

			return true;
		}

		/// <summary>
		/// State serlialization
		/// </summary>
		public override void SyncState(Serializer ser)
		{
			ser.BeginSection("Plus3FloppyDisk");

			ser.Sync(nameof(CylinderCount), ref CylinderCount);
			ser.Sync(nameof(SideCount), ref SideCount);
			ser.Sync(nameof(BytesPerTrack), ref BytesPerTrack);
			ser.Sync(nameof(WriteProtected), ref WriteProtected);
			ser.SyncEnum(nameof(Protection), ref Protection);

			ser.Sync(nameof(DirtyData), ref DirtyData);
			if (DirtyData)
			{

			}

			// sync deterministic track and sector counters
			ser.Sync(nameof(_randomCounter), ref _randomCounter);
			RandomCounter = _randomCounter;

			ser.EndSection();
		}
	}
}