Organized the project files.

And also fixed some bugs.

PriFileFormat/SubStream.cs

@@ -0,0 +1,76 @@
+using System;
+using System.IO;
+using System.Runtime.InteropServices;
+namespace PriFileFormat
+{
+	public class SubStream: Stream
+	{
+		Stream baseStream;
+		long subStreamPosition;
+		long subStreamLength;
+
+		public SubStream (Stream baseStream, long subStreamPosition, long subStreamLength)
+		{
+			this.baseStream = baseStream;
+			this.subStreamPosition = subStreamPosition;
+			this.subStreamLength = subStreamLength;
+		}
+
+		public long SubStreamPosition => subStreamPosition;
+
+		public override bool CanRead => baseStream.CanRead;
+
+		public override bool CanSeek => baseStream.CanSeek;
+
+		public override bool CanWrite => false;
+
+		public override long Length => subStreamLength;
+
+		public override long Position
+		{
+			get { return baseStream.Position - subStreamPosition; }
+			set { baseStream.Position = subStreamPosition + value; }
+		}
+
+		public override void Flush ()
+		{
+		}
+
+		public override int Read (byte [] buffer, int offset, int count)
+		{
+			if (Position < 0)
+				throw new InvalidOperationException ("Cannot read when position is negative.");
+			if (Position + count > subStreamLength)
+				count = (int)(subStreamLength - Position);
+
+			return baseStream.Read (buffer, offset, count);
+		}
+
+		public override long Seek (long offset, SeekOrigin origin)
+		{
+			switch (origin)
+			{
+				case SeekOrigin.Begin:
+					return baseStream.Seek (subStreamPosition + offset, SeekOrigin.Begin) - subStreamPosition;
+				case SeekOrigin.Current:
+					return baseStream.Seek (offset, SeekOrigin.Current) - subStreamPosition;
+				case SeekOrigin.End:
+					return baseStream.Seek (subStreamPosition + subStreamLength + offset, SeekOrigin.Begin) - subStreamPosition;
+				default:
+					throw new ArgumentException ("Invalid origin.", nameof (origin));
+			}
+		}
+
+		public override void SetLength (long value)
+		{
+			throw new NotSupportedException ();
+		}
+
+		public override void Write (byte [] buffer, int offset, int count)
+		{
+			throw new NotSupportedException ();
+		}
+
+		~SubStream () { baseStream = null; }
+	}
+}