Update about Manager.

PriFormat/SubStream.cs

@@ -0,0 +1,110 @@
+using System;
+using System.IO;
+
+namespace PriFormat
+{
+	internal sealed class SubStream: Stream
+	{
+		private readonly Stream _baseStream;
+		private readonly long _baseOffset;
+		private readonly long _length;
+		private long _position;
+
+		public SubStream (Stream baseStream, long offset, long length)
+		{
+			if (baseStream == null)
+				throw new ArgumentNullException ("baseStream");
+			if (!baseStream.CanSeek)
+				throw new ArgumentException ("Base stream must be seekable.");
+
+			_baseStream = baseStream;
+			_baseOffset = offset;
+			_length = length;
+			_position = 0;
+		}
+
+		public override bool CanRead { get { return true; } }
+		public override bool CanSeek { get { return true; } }
+		public override bool CanWrite { get { return false; } }
+
+		public override long Length
+		{
+			get { return _length; }
+		}
+
+		public override long Position
+		{
+			get { return _position; }
+			set
+			{
+				if (value < 0 || value > _length)
+					throw new ArgumentOutOfRangeException ("value");
+				_position = value;
+			}
+		}
+
+		public override int Read (byte [] buffer, int offset, int count)
+		{
+			if (buffer == null)
+				throw new ArgumentNullException ("buffer");
+			if (offset < 0 || count < 0 || buffer.Length - offset < count)
+				throw new ArgumentOutOfRangeException ();
+
+			long remaining = _length - _position;
+			if (remaining <= 0)
+				return 0;
+
+			if (count > remaining)
+				count = (int)remaining;
+
+			_baseStream.Position = _baseOffset + _position;
+			int read = _baseStream.Read (buffer, offset, count);
+			_position += read;
+			return read;
+		}
+
+		public override long Seek (long offset, SeekOrigin origin)
+		{
+			long target;
+
+			switch (origin)
+			{
+				case SeekOrigin.Begin:
+					target = offset;
+					break;
+
+				case SeekOrigin.Current:
+					target = _position + offset;
+					break;
+
+				case SeekOrigin.End:
+					target = _length + offset;
+					break;
+
+				default:
+					throw new ArgumentException ("origin");
+			}
+
+			if (target < 0 || target > _length)
+				throw new IOException ("Seek out of range.");
+
+			_position = target;
+			return _position;
+		}
+
+		public override void Flush ()
+		{
+			// no-op (read-only)
+		}
+
+		public override void SetLength (long value)
+		{
+			throw new NotSupportedException ();
+		}
+
+		public override void Write (byte [] buffer, int offset, int count)
+		{
+			throw new NotSupportedException ();
+		}
+	}
+}