DiscStructure.cs

using System;
using System.Text;
using System.Collections.Generic;

namespace BizHawk.Emulation.DiscSystem
{
	/// <summary>
	/// Contains structural information for the disc broken down into c# data structures for easy interrogation.
	/// This represents a best-effort interpretation of the raw disc image.
	/// NOTE: Since this ended up really just having the list of sessions.. maybe it isn't needed and can just float on up into Disc
	/// </summary>
	public class DiscStructure
	{
		/// <summary>
		/// This is a 1-indexed list of sessions (session 1 is at [1])
		/// Support for multiple sessions is thoroughly not working yet
		/// </summary>
		public List<Session> Sessions = new List<Session>();

		public class Session
		{
			//Notable omission:
				//Length of the session
				//How should this be defined? It's even harder than determining a track length

			/// <summary>
			/// The LBA of the session's leadout. In other words, for all intents and purposes, the end of the session
			/// </summary>
			public int LeadoutLBA { get { return LeadoutTrack.LBA; } }

			/// <summary>
			/// The session number
			/// </summary>
			public int Number;

			/// <summary>
			/// The number of user information tracks in the session.
			/// This excludes the lead-in and lead-out tracks
			/// Use this instead of Tracks.Count
			/// </summary>
			public int InformationTrackCount { get { return Tracks.Count - 2; } }

			/// <summary>
			/// All the tracks in the session.. but... Tracks[0] is the lead-in track. Tracks[1] should be "Track 1". So beware of this.
			/// For a disc with "3 tracks", Tracks.Count will be 5: it includes that lead-in track as well as the leadout track.
			/// Perhaps we should turn this into a special collection type with no Count or Length, or a method to GetTrack()
			/// </summary>
			public List<Track> Tracks = new List<Track>();

			/// <summary>
			/// A reference to the first information track (Track 1)
			/// The raw TOC may have specified something different; it's not clear how this discrepancy is handled.
			/// </summary>
			public Track FirstInformationTrack { get { return Tracks[1]; } }

			/// <summary>
			/// A reference to the last information track on the disc.
			/// The raw TOC may have specified something different; it's not clear how this discrepancy is handled.
			/// </summary>
			public Track LastInformationTrack { get { return Tracks[InformationTrackCount]; } }

			/// <summary>
			/// A reference to the lead-out track.
			/// Effectively, the end of the user area of the disc.
			/// </summary>
			public Track LeadoutTrack { get { return Tracks[Tracks.Count - 1]; } }

			/// <summary>
			/// A reference to the lead-in track
			/// </summary>
			public Track LeadinTrack { get { return Tracks[0]; } }

			/// <summary>
			/// Determines which track of the session is at the specified LBA.
			/// </summary>
			public Track SeekTrack(int lba)
			{
				var ses = this;

				for (int i = 1; i < Tracks.Count; i++)
				{
					var track = ses.Tracks[i];
					//funny logic here: if the current track's LBA is > the requested track number, it means the previous track is the one we wanted
					if (track.LBA > lba)
						return ses.Tracks[i - 1];
				}
				return ses.LeadoutTrack;
			}
		}

		/// <summary>
		/// The Type of a track as specified in the TOC Q-Subchannel data from the control flags.
		/// Could also be 4-Channel Audio, but we'll handle that later if needed
		/// </summary>
		public enum ETrackType
		{
			/// <summary>
			/// The track type isn't always known.. it can take this value til its populated
			/// </summary>
			Unknown,

			/// <summary>
			/// Data track( TOC Q control 0x04 flag set )
			/// </summary>
			Data,

			/// <summary>
			/// Audio track( TOC Q control 0x04 flag clear )
			/// </summary>
			Audio
		}

		/// <summary>
		/// Information about a Track.
		/// </summary>
		public class Track
		{
			//Notable omission: 
				//a list of Indices. It's difficult to reliably construct it.
				//Notably, mednafen can't readily produce it.
				//Indices may need scanning sector by sector. 
				//It's unlikely that any software would be needing indices anyway.
				//We should add another index scanning service if that's ever needed.
				//(note: a CCD should contain indices, but it's not clear whether it's required. logically it shouldnt be)
			//Notable omission:
				//Length of the track.
				//How should this be defined? Between which indices? It's really hard.

			//These omissions could be handled by ReadStructure() policies which permit the scanning of the entire disc.
			//After that, they could be cached in here.
			
			/// <summary>
			/// The number of the track (1-indexed)
			/// </summary>
			public int Number;

			/// <summary>
			/// The Mode of the track (0 is Audio, 1 and 2 are data)
			/// This is heuristically determined.
			/// Actual sector contents may vary
			/// </summary>
			public int Mode;

			/// <summary>
			/// Is this track a Data track?
			/// </summary>
			public bool IsData { get { return !IsAudio; } }

			/// <summary>
			/// Is this track an Audio track?
			/// </summary>
			public bool IsAudio { get { return Mode == 0; } }

			/// <summary>
			/// The 'control' properties of the track expected to be found in the track's subQ.
			/// However, this is what's indicated by the disc TOC.
			/// Actual sector contents may vary.
			/// </summary>
			public EControlQ Control;

			/// <summary>
			/// The starting LBA of the track (index 1).
			/// </summary>
			public int LBA;

			/// <summary>
			/// The next track in the session. null for the leadout track of a session.
			/// </summary>
			public Track NextTrack;
		}

		public class Index
		{
			public int Number;
			public int LBA;
		}

	}

}