--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Util/PrebufferingStream.cs	Tue Jan 08 16:38:21 2013 +0100
@@ -0,0 +1,238 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.IO;
+using System.Threading;
+
+namespace UCIS.Util {
+	public class PrebufferingStream : Stream {
+		class AsyncResult : AsyncResultBase {
+			public int Count { get; private set; }
+			public int Left { get; set; }
+			public AsyncResult(AsyncCallback callback, Object state) : base(callback, state) { }
+			public void SetCompleted(Boolean synchronously, int count, Exception error) {
+				this.Count = count;
+				base.SetCompleted(synchronously, error);
+			}
+			public int WaitForCompletion() {
+				WaitHandle wh = null;
+				lock (this) if (!IsCompleted) wh = AsyncWaitHandle;
+				if (wh != null) wh.WaitOne();
+				ThrowError();
+				return Count;
+			}
+		}
+
+		Stream baseStream;
+		Byte[] prebuffer = null;
+		int prebufferoffset = 0;
+		int prebuffercount = 0;
+		int defaultbuffersize;
+
+		public Stream BaseStream { get { return baseStream; } }
+
+		public PrebufferingStream(Stream stream) : this(stream, 1024) { }
+		public PrebufferingStream(Stream stream, int bufferSize) {
+			if (stream == null) throw new ArgumentNullException("stream");
+			baseStream = stream;
+			defaultbuffersize = bufferSize;
+		}
+
+		public IAsyncResult BeginPrebuffering(AsyncCallback callback, Object state) {
+			return BeginPrebuffering(1, callback, state);
+		}
+		public IAsyncResult BeginPrebuffering(int count, AsyncCallback callback, Object state) {
+			AsyncResult ar = new AsyncResult(callback, state);
+			if (prebuffercount > count) {
+				ar.SetCompleted(true, count, null);
+			} else {
+				PrepareBuffer(count);
+				int off = prebufferoffset + prebuffercount;
+				baseStream.BeginRead(prebuffer, off, prebuffer.Length - off, asyncPrebufferReadCallback, ar);
+			}
+			return ar;
+		}
+		private void asyncPrebufferReadCallback(IAsyncResult ar) {
+			AsyncResult myar = (AsyncResult)ar.AsyncState;
+			try {
+				int len = baseStream.EndRead(ar);
+				if (len <= 0) {
+					myar.SetCompleted(false, prebuffercount, null);
+				} else {
+					myar.Left -= len;
+					prebuffercount += len;
+					if (myar.Left > 0) {
+						int off = prebufferoffset + prebuffercount;
+						baseStream.BeginRead(prebuffer, off, prebuffer.Length - off, asyncPrebufferReadCallback, myar);
+					} else {
+						myar.SetCompleted(false, prebuffercount, null);
+					}
+				}
+			} catch (Exception ex) {
+				myar.SetCompleted(false, prebuffercount, ex);
+			}
+		}
+		public int EndPrebuffering(IAsyncResult ar) {
+			AsyncResult myar = (AsyncResult)ar;
+			return myar.WaitForCompletion();
+		}
+		public int Prebuffer() {
+			return Prebuffer(1);
+		}
+		public int Prebuffer(int count) {
+			count -= prebuffercount;
+			if (count <= 0) return prebuffercount;
+			PrepareBuffer(prebuffercount + count);
+			while (count > 0) {
+				int off = prebufferoffset + prebuffercount;
+				int len = baseStream.Read(prebuffer, off, prebuffer.Length - off);
+				if (len <= 0) return prebuffercount;
+				count -= len;
+				prebuffercount += len;
+			}
+			return prebuffercount;
+		}
+		private void PrepareBuffer(int count) {
+			if (prebuffercount == 0) prebufferoffset = 0;
+			if (prebuffer == null || (prebuffercount == 0 && prebuffer.Length > defaultbuffersize)) {
+				if (count < defaultbuffersize) count = defaultbuffersize;
+				prebuffer = new Byte[count];
+				prebufferoffset = 0;
+			} else if (prebufferoffset + count > prebuffer.Length) {
+				if (count > prebuffer.Length) {
+					Byte[] newbuffer = new Byte[prebuffercount + count];
+					Buffer.BlockCopy(prebuffer, prebufferoffset, newbuffer, 0, prebuffercount);
+					prebuffer = newbuffer;
+				} else {
+					Buffer.BlockCopy(prebuffer, prebufferoffset, prebuffer, 0, prebuffercount);
+				}
+				prebufferoffset = 0;
+			}
+		}
+		public Byte Peek() {
+			return Peek(0);
+		}
+		public Byte Peek(int offset) {
+			if (Prebuffer(offset + 1) < offset + 1) throw new EndOfStreamException();
+			return prebuffer[prebufferoffset + offset];
+		}
+		public void Peek(Byte[] buffer, int offset, int count) {
+			Peek(buffer, offset, 0, count);
+		}
+		public void Peek(Byte[] buffer, int bufferoffset, int peekoffset, int count) {
+			if (Prebuffer(peekoffset + count) < peekoffset + count) throw new EndOfStreamException();
+			Buffer.BlockCopy(prebuffer, prebufferoffset + peekoffset, buffer, bufferoffset, count);
+		}
+		public int TryPeek() {
+			return TryPeek(0);
+		}
+		public int TryPeek(int offset) {
+			if (prebuffercount <= offset) return -1;
+			return prebuffer[prebufferoffset + offset];
+		}
+		public int TryPeek(Byte[] buffer, int offset, int count) {
+			return TryPeek(buffer, offset, 0, count);
+		}
+		public int TryPeek(Byte[] buffer, int bufferoffset, int peekoffset, int count) {
+			if (prebuffercount < peekoffset + count) count = prebuffercount - peekoffset;
+			if (count < 0) count = 0;
+			if (count > 0) Buffer.BlockCopy(prebuffer, prebufferoffset + peekoffset, buffer, bufferoffset, count);
+			return count;
+		}
+
+		public override int Read(byte[] buffer, int offset, int count) {
+			if (prebuffercount > 0 || count < 16) {
+				if (prebuffercount == 0) if (Prebuffer() < 1) return 0;
+				if (count > prebuffercount) count = prebuffercount;
+				Buffer.BlockCopy(prebuffer, prebufferoffset, buffer, offset, count);
+				prebufferoffset += count;
+				prebuffercount -= count;
+				return count;
+			} else {
+				return baseStream.Read(buffer, offset, count);
+			}
+		}
+
+		public override int ReadByte() {
+			if (Prebuffer(1) < 1) return -1;
+			int v = prebuffer[prebufferoffset];
+			prebufferoffset++;
+			prebuffercount--;
+			return v;
+		}
+
+		public override IAsyncResult BeginRead(byte[] buffer, int offset, int count, AsyncCallback callback, object state) {
+			if (prebuffercount > 0) {
+				if (count > prebuffercount) count = prebuffercount;
+				Buffer.BlockCopy(prebuffer, prebufferoffset, buffer, offset, count);
+				prebufferoffset += count;
+				prebuffercount -= count;
+				AsyncResult ar = new AsyncResult(callback, state);
+				ar.SetCompleted(true, count, null);
+				return ar;
+			} else {
+				return baseStream.BeginRead(buffer, offset, count, callback, state);
+			}
+		}
+
+		public override int EndRead(IAsyncResult asyncResult) {
+			AsyncResult myar = asyncResult as AsyncResult;
+			if (myar != null) {
+				return myar.WaitForCompletion();
+			} else {
+				return baseStream.EndRead(asyncResult);
+			}
+		}
+
+		public override void Close() {
+			base.Close();
+			baseStream.Close();
+		}
+
+		public override void Write(byte[] buffer, int offset, int count) {
+			baseStream.Write(buffer, offset, count);
+		}
+
+		public override void WriteByte(byte value) {
+			baseStream.WriteByte(value);
+		}
+
+		public override IAsyncResult BeginWrite(byte[] buffer, int offset, int count, AsyncCallback callback, object state) {
+			return baseStream.BeginWrite(buffer, offset, count, callback, state);
+		}
+
+		public override void EndWrite(IAsyncResult asyncResult) {
+			baseStream.EndWrite(asyncResult);
+		}
+
+		public override int ReadTimeout {
+			get { return baseStream.ReadTimeout; }
+			set { baseStream.ReadTimeout = value; }
+		}
+
+		public override int WriteTimeout {
+			get { return baseStream.WriteTimeout; }
+			set { baseStream.WriteTimeout = value; }
+		}
+
+		public override long Length { get { return prebuffercount + baseStream.Length; } }
+		public override long Position {
+			get { return baseStream.Position - prebuffercount; }
+			set { throw new NotImplementedException(); }
+		}
+
+		public override void SetLength(long value) { throw new NotImplementedException(); }
+		public override long Seek(long offset, SeekOrigin origin) { throw new NotImplementedException(); }
+
+		public override bool CanRead { get { return prebuffercount > 0 || baseStream.CanRead; } }
+		public override bool CanSeek { get { return false; } }
+		public override bool CanTimeout { get { return baseStream.CanTimeout; } }
+		public override bool CanWrite { get { return baseStream.CanWrite; } }
+
+		public int Buffered { get { return prebuffercount; } }
+
+		public override void Flush() {
+			baseStream.Flush();
+		}
+	}
+}