BizHawk/BizHawk.Emulation.DiscSystem/SectorInterfaces.cs

using System;
using System.IO;

namespace BizHawk.Emulation.DiscSystem
{
	public interface ISector
	{
		/// <summary>
		/// reads the entire sector, raw
		/// </summary>
		int Read_2352(byte[] buffer, int offset);

		/// <summary>
		/// reads 2048 bytes of userdata.. precisely what this means isnt always 100% certain (for instance mode2 form 0 has 2336 bytes of userdata instead of 2048)..
		/// ..but its certain enough for this to be useful
		/// </summary>
		int Read_2048(byte[] buffer, int offset);
	}


	/// <summary>
	/// this ISector is dumb and only knows how to drag chunks off a source blob
	/// </summary>
	public class Sector_RawBlob : ISector
	{
		public IBlob Blob;
		public long Offset;
		public int Read_2352(byte[] buffer, int offset)
		{
			return Blob.Read(Offset, buffer, offset, 2352);
		}
		public int Read_2048(byte[] buffer, int offset)
		{
			//this depends on CD-XA mode and such. so we need to read the mode bytes
			//HEY!!!!!! SHOULD THIS BE DONE BASED ON THE CLAIMED TRACK TYPE, OR ON WHATS IN THE SECTOR?
			//this is kind of a function of the CD reader.. it's not clear how this function should work.
			//YIKES!!!!!!!!!!!!!!
			//well, we need to scrutinize it for CCD files anyway, so...
			//this sucks.
			Blob.Read(Offset + 16, buffer, 0, 1);
			byte mode = buffer[0];
			if(mode == 1)
				return Blob.Read(Offset + 16, buffer, offset, 2048);
			else
				return Blob.Read(Offset + 24, buffer, offset, 2048);
		}
	}

	/// <summary>
	/// this ISector always returns zeroes
	/// </summary>
	class Sector_Zero : ISector
	{
		public int Read_2352(byte[] buffer, int offset)
		{
			Array.Clear(buffer, 0, 2352);
			return 2352;
		}
		public int Read_2048(byte[] buffer, int offset)
		{
			Array.Clear(buffer, 0, 2048);
			return 2048;
		}
	}

	abstract class Sector_Mode1_or_Mode2_2352 : ISector
	{
		public ISector BaseSector;
		public abstract int Read_2352(byte[] buffer, int offset);
		public abstract int Read_2048(byte[] buffer, int offset);
	}

	/// <summary>
	/// This ISector is a raw MODE1 sector
	/// </summary>
	class Sector_Mode1_2352 : Sector_Mode1_or_Mode2_2352
	{
		public override int Read_2352(byte[] buffer, int offset)
		{
			return BaseSector.Read_2352(buffer, offset);
		}
		public override int Read_2048(byte[] buffer, int offset)
		{
			//to get 2048 bytes out of this sector type, start 16 bytes in
			int ret = BaseSector.Read_2352(TempSector, 0);
			Buffer.BlockCopy(TempSector, 16, buffer, offset, 2048);
			System.Diagnostics.Debug.Assert(buffer != TempSector);
			return 2048;
		}

		[ThreadStatic]
		static byte[] TempSector = new byte[2352];
	}

	/// <summary>
	/// this ISector is a raw MODE2 sector. could be form 0,1,2... who can say? supposedly:
	/// To tell the different Mode 2s apart you have to examine bytes 16-23 of the sector (the first 8 bytes of Mode Data). 
	/// If bytes 16-19 are not the same as 20-23, then it is Mode 2. If they are equal and bit 5 is on (0x20), then it is Mode 2 Form 2. Otherwise it is Mode 2 Form 1.
	/// ...but we're not using this information in any way
	/// </summary>
	class Sector_Mode2_2352 : Sector_Mode1_or_Mode2_2352
	{
		public override int Read_2352(byte[] buffer, int offset)
		{
			return BaseSector.Read_2352(buffer, offset);
		}

		public override int Read_2048(byte[] buffer, int offset)
		{
			//to get 2048 bytes out of this sector type, start 24 bytes in
			int ret = BaseSector.Read_2352(TempSector, 0);
			Buffer.BlockCopy(TempSector, 24, buffer, offset, 2048);
			System.Diagnostics.Debug.Assert(buffer != TempSector);
			return 2048;
		}

		[ThreadStatic]
		static byte[] TempSector = new byte[2352];
	}

	//a blob that also has an ECM cache associated with it. maybe one day.
	class ECMCacheBlob
	{
		public ECMCacheBlob(IBlob blob)
		{
			BaseBlob = blob;
		}
		public IBlob BaseBlob;
	}

	/// <summary>
	/// this ISector is a MODE1 sector that is generating itself from an underlying MODE1/2048 userdata piece
	/// </summary>
	class Sector_Mode1_2048 : ISector
	{
		public Sector_Mode1_2048(int ABA)
		{
			byte aba_min = (byte)(ABA / 60 / 75);
			byte aba_sec = (byte)((ABA / 75) % 60);
			byte aba_frac = (byte)(ABA % 75);
			bcd_aba_min = aba_min.BCD_Byte();
			bcd_aba_sec = aba_sec.BCD_Byte();
			bcd_aba_frac = aba_frac.BCD_Byte();
		}
		byte bcd_aba_min, bcd_aba_sec, bcd_aba_frac;

		public ECMCacheBlob Blob;
		public long Offset;
		byte[] extra_data;
		bool has_extra_data;

		public int Read_2048(byte[] buffer, int offset)
		{
			//this is easy. we only have 2048 bytes, and 2048 bytes were requested
			return Blob.BaseBlob.Read(Offset, buffer, offset, 2048);
		}

		public int Read_2352(byte[] buffer, int offset)
		{
			//user data
			int read = Blob.BaseBlob.Read(Offset, buffer, offset + 16, 2048);

			//if we read the 2048 physical bytes OK, then return the complete sector
			if (read == 2048 && has_extra_data)
			{
				Buffer.BlockCopy(extra_data, 0, buffer, offset, 16);
				Buffer.BlockCopy(extra_data, 16, buffer, offset + 2064, 4 + 8 + 172 + 104);
				return 2352;
			}

			//sync
			buffer[offset + 0] = 0x00; buffer[offset + 1] = 0xFF; buffer[offset + 2] = 0xFF; buffer[offset + 3] = 0xFF;
			buffer[offset + 4] = 0xFF; buffer[offset + 5] = 0xFF; buffer[offset + 6] = 0xFF; buffer[offset + 7] = 0xFF;
			buffer[offset + 8] = 0xFF; buffer[offset + 9] = 0xFF; buffer[offset + 10] = 0xFF; buffer[offset + 11] = 0x00;
			//sector address
			buffer[offset + 12] = bcd_aba_min;
			buffer[offset + 13] = bcd_aba_sec;
			buffer[offset + 14] = bcd_aba_frac;
			//mode 1
			buffer[offset + 15] = 1;

			//calculate EDC and poke into the sector
			uint edc = ECM.EDC_Calc(buffer, offset, 2064);
			ECM.PokeUint(buffer, 2064, edc);

			//intermediate
			for (int i = 0; i < 8; i++) buffer[offset + 2068 + i] = 0;
			//ECC
			ECM.ECC_Populate(buffer, offset, buffer, offset, false);

			//VALIDATION - check our homemade algorithms against code derived from ECM
			////EDC
			//GPL_ECM.edc_validateblock(buffer, 2064, buffer, offset + 2064);
			////ECC
			//GPL_ECM.ecc_validate(buffer, offset, false);

			//if we read the 2048 physical bytes OK, then return the complete sector
			if (read == 2048)
			{
				extra_data = new byte[16 + 4 + 8 + 172 + 104];
				Buffer.BlockCopy(buffer, 0, extra_data, 0, 16);
				Buffer.BlockCopy(buffer, 2064, extra_data, 16, 4 + 8 + 172 + 104);
				has_extra_data = true;
				return 2352;
			}
			//otherwise, return a smaller value to indicate an error
			else return read;
		}
	}
}