Custom ISO Stream for full CDROM support

SabreTools.Serialization/Extensions/CDROM.cs

@@ -0,0 +1,275 @@
+using System;
+using System.IO;
+using SabreTools.Data.Models.CDROM;
+using SabreTools.IO;
+using SabreTools.IO.Extensions;
+
+namespace SabreTools.Data.Extensions
+{
+    public static class CDROM
+    {
+        /// <summary>
+        /// Creates a stream that provides only the user data of a CDROM stream
+        /// </summary>
+        public class ISO9660Stream : Stream
+        {
+            // Base CDROM stream (2352-byte sector)
+            private readonly Stream _baseStream;
+
+            // State variables
+            private long _position = 0;
+            private SectorMode _currentMode = SectorMode.UNKNOWN;
+            private long _userDataStart = 16;
+            private long _userDataEnd = 2064;
+            private long _isoSectorSize = Constants.Mode1DataSize;
+
+            public ISO9660Stream(Stream inputStream)
+            {
+                if (!inputStream.CanSeek || !inputStream.CanRead)
+                    throw new ArgumentException("Stream must be readable and seekable.", nameof(inputStream));
+                _baseStream = inputStream;
+            }
+
+            public override bool CanRead => true;
+            public override bool CanSeek => true;
+            public override bool CanWrite => false;
+
+            public override void Flush()
+            {
+                _baseStream.Flush();
+            }
+
+            public override long Length
+            {
+                get
+                {
+                    return (_baseStream.Length / Constants.CDROMSectorSize) * _isoSectorSize;
+                }
+            }
+
+            public override void SetLength(long value)
+            {
+                throw new NotSupportedException("Setting the length of this stream is not supported.");
+            }
+
+            public override void Write(byte[] buffer, int offset, int count)
+            {
+                throw new NotSupportedException("Writing to this stream is not supported.");
+            }
+
+            protected override void Dispose(bool disposing)
+            {
+                if (disposing)
+                {
+                    _baseStream.Dispose();
+                }
+                base.Dispose(disposing);
+            }
+
+            public override long Position
+            {
+                // Get the position of the underlying ISO9660 stream
+                get
+                {
+                    // Get the user data location based on the current sector mode
+                    SetState(_position);
+
+                    // Get the number of ISO sectors before current position
+                    long isoPosition = (_position / Constants.CDROMSectorSize) * _isoSectorSize;
+
+                    // Add the within-sector position
+                    long remainder = _position % Constants.CDROMSectorSize;
+                    if (remainder > _userDataEnd)
+                        isoPosition += _isoSectorSize;
+                    else if (remainder > _userDataStart)
+                        isoPosition += remainder - _userDataStart;
+
+                    return isoPosition;
+                }
+                set
+                {
+                    // Seek to the underlying ISO9660 position
+                    Seek(value, SeekOrigin.Begin);
+                }
+            }
+
+            public override int Read(byte[] buffer, int offset, int count)
+            {
+                bool readEntireSector = false;
+                int totalRead = 0;
+                int remaining = count;
+
+                while (remaining > 0 && _position < _baseStream.Length)
+                {
+                    // Determine location of current sector
+                    long baseStreamOffset = (_position / Constants.CDROMSectorSize) * Constants.CDROMSectorSize;
+
+                    // Set the current sector's mode and user data location
+                    SetState(baseStreamOffset);
+
+                    // Deal with case where base position is not in ISO stream
+                    long remainder = _position % Constants.CDROMSectorSize;
+                    long sectorOffset = remainder - _userDataStart;
+                    if (remainder < _userDataStart)
+                    {
+                        baseStreamOffset += _userDataStart;
+                        sectorOffset = 0;
+                        _position += _userDataStart;
+                    }
+                    else if (remainder >= _userDataEnd)
+                    {
+                        baseStreamOffset += Constants.CDROMSectorSize;
+                        sectorOffset = 0;
+                        _position += Constants.CDROMSectorSize - _userDataEnd + _userDataStart;
+                    }
+                    else
+                        baseStreamOffset += remainder;
+
+                    // Sanity check on read location before seeking
+                    if (baseStreamOffset < 0 || baseStreamOffset > _baseStream.Length)
+                    {
+                        throw new ArgumentOutOfRangeException(nameof(offset), "Attempted to seek outside the stream boundaries.");
+                    }
+
+                    // Seek to target position in base CDROM stream
+                    _baseStream.Seek(baseStreamOffset, SeekOrigin.Begin);
+
+                    // Read the remaining bytes, up to max of one ISO sector (2048 bytes)
+                    int bytesToRead = (int)Math.Min(remaining, _isoSectorSize - sectorOffset);
+
+                    // Don't overshoot end of stream
+                    bytesToRead = (int)Math.Min(bytesToRead, _baseStream.Length - _position);
+
+                    if (bytesToRead == (_isoSectorSize - sectorOffset))
+                        readEntireSector = true;
+                    else
+                        readEntireSector = false;
+
+                    // Finish reading if no more bytes to be read
+                    if (bytesToRead <= 0)
+                        break;
+
+                    // Read up to 2048 bytes from base CDROM stream
+                    int bytesRead = _baseStream.Read(buffer, offset + totalRead, bytesToRead);
+
+                    // Update state for base stream
+                    _position = _baseStream.Position;
+                    if (readEntireSector)
+                        _position += (Constants.CDROMSectorSize - _userDataEnd) + _userDataStart;
+
+                    // Update state for ISO stream
+                    totalRead += bytesRead;
+                    remaining -= bytesRead;
+
+                    if (bytesRead == 0)
+                        break;
+                }
+
+                return totalRead;
+            }
+
+            public override long Seek(long offset, SeekOrigin origin)
+            {
+                // Get the intended position for the ISO9660 stream
+                long targetPosition;
+                switch (origin)
+                {
+                    case SeekOrigin.Begin:
+                        targetPosition = offset;
+                        break;
+                    case SeekOrigin.Current:
+                        targetPosition = Position + offset;
+                        break;
+                    case SeekOrigin.End:
+                        targetPosition = Length + offset;
+                        break;
+                    default:
+                        throw new ArgumentException("Invalid SeekOrigin.", nameof(origin));
+                }
+
+                // Get the number of ISO sectors before current position
+                long newPosition = (targetPosition / _isoSectorSize) * Constants.CDROMSectorSize;
+
+                // Set the current sector's mode and user data location
+                SetState(newPosition);
+
+                // Add the within-sector position
+                newPosition += _userDataStart + (targetPosition % _isoSectorSize);
+
+                if (newPosition < 0 || newPosition > _baseStream.Length)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(offset), "Attempted to seek outside the stream boundaries.");
+                }
+
+                _position = _baseStream.Seek(newPosition, SeekOrigin.Begin);
+                return Position;
+            }
+
+            private void SetState(long sectorLocation)
+            {
+                long oldPosition = _baseStream.Position;
+                long modePosition = (sectorLocation - sectorLocation % Constants.CDROMSectorSize) + 15;
+                _baseStream.Seek(modePosition, SeekOrigin.Begin);
+                byte modeByte = _baseStream.ReadByteValue();
+                if (modeByte == 0)
+                    _currentMode = SectorMode.MODE0;
+                else if (modeByte == 1)
+                    _currentMode = SectorMode.MODE1;
+                else if (modeByte == 2)
+                {
+                    _baseStream.Seek(modePosition + 3, SeekOrigin.Begin);
+                    byte submode = _baseStream.ReadByteValue();
+                    if ((submode & 0x20) == 0x20)
+                        _currentMode = SectorMode.MODE2_FORM2;
+                    else
+                        _currentMode = SectorMode.MODE2_FORM1;
+                }
+                else
+                    _currentMode = SectorMode.UNKNOWN;
+
+                // Set the user data location variables
+                switch (_currentMode)
+                {
+                    case SectorMode.MODE1:
+                        _userDataStart = 16;
+                        _userDataEnd = 2064;
+                        //_isoSectorSize = Constants.Mode1DataSize;
+                        break;
+
+                    case SectorMode.MODE2_FORM1:
+                        _userDataStart = 24;
+                        _userDataEnd = 2072;
+                        //_isoSectorSize = Constants.Form1DataSize;
+                        break;
+
+                    case SectorMode.MODE2_FORM2:
+                        _userDataStart = 24;
+                        _userDataEnd = 2072;
+                        // TODO: Support flexible sector length
+                        //_userDataEnd = 2348;
+                        //_isoSectorSize = Constants.Form2DataSize;
+                        break;
+
+                    case SectorMode.MODE0:
+                    case SectorMode.MODE2:
+                        _userDataStart = 16;
+                        _userDataEnd = 2064;
+                        // TODO: Support flexible sector length
+                        //_userDataEnd = 2352;
+                        //_isoSectorSize = Constants.Mode0DataSize;
+                        break;
+
+                    case SectorMode.UNKNOWN:
+                        _userDataStart = 16;
+                        _userDataEnd = 2064;
+                        //_isoSectorSize = Constants.Mode1DataSize;
+                        break;
+                }
+
+                _baseStream.Seek(oldPosition, SeekOrigin.Begin);
+
+                return;
+            }
+        }
+    }
+}

SabreTools.Serialization/Models/CDROM/CDROM.cs

@@ -1,15 +1,16 @@
 namespace SabreTools.Data.Models.CDROM
 {
     /// <summary>
-    /// A CD-ROM disc image, made up of multiple data tracks, ISO 10149 / ECMA-130
-    /// Specifically not a mixed-mode CD disc image, pure CD-ROM disc
+    /// A CD-ROM disc image, made up of data sectors, ISO 10149 / ECMA-130
+    /// Intentionally not a mixed-mode CD disc image, pure CD-ROM disc (no audio sectors)
+    /// This model intentionally does not take tracks into consideration
     /// </summary>
     /// <see href="https://ecma-international.org/wp-content/uploads/ECMA-130_2nd_edition_june_1996.pdf"/>
     public sealed class CDROM
     {
         /// <summary>
-        /// CD-ROM data tracks
+        /// CD-ROM data sectors
         /// </summary>
-        public DataTrack[] Tracks { get; set; } = [];
+        public DataSector[] Sectors { get; set; } = [];
     }
 }