Implement BufferManager.cs

svn path=/branches/mono-2-6/mcs/; revision=154998

1 files changed, 152 insertions, 20 deletions

diff --git a/mcs/class/System.ServiceModel/System.ServiceModel.Channels/BufferManager.cs b/mcs/class/System.ServiceModel/System.ServiceModel.Channels/BufferManager.cs
index 9078b9d1cdd..ae295d08b0a 100644
--- a/mcs/class/System.ServiceModel/System.ServiceModel.Channels/BufferManager.cs
+++ b/mcs/class/System.ServiceModel/System.ServiceModel.Channels/BufferManager.cs
@@ -1,9 +1,38 @@
 //
-// BufferManager.cs
+// BufferManager.cs:
+//    This class suffers from an engineering problem in its
+//    design: when this API is used to limit the total pool
+//    size it will throw, but no user code is designed to
+//    cope with that.
 //
-// Author: Atsushi Enomoto (atsushi@ximian.com)
+//    Instead of the Microsoft strategy, we allow allocation
+//    to go as far as it wants to go and merely allow this
+//    to be a pool that can be used recycle buffers.
 //
-// Copyright (C) 2005 Novell, Inc (http://www.novell.com)
+//    This still gives us the main benefit of this class, while
+//    avoiding the potential crashing scenarios and simplifies
+//    the implementation significantly from what has been
+//    document in the blogosphere.
+//
+//    There are a few problems: for example, if we do not find
+//    a buffer of the proper size in the expected slot, say
+//    a 31k buffer in the slot for [32k-64k] values, we will
+//    allocate a new buffer, even if there might have been a
+//    buffer for 128k.
+//
+// A few considerations:
+//
+//    The size of an empty array is either 16 on 32 bit systems
+//    and 32 bytes in 64 bit systems.
+//
+//    We take this information into account for the minimum allocation
+//    pools.
+//
+// Authors:
+//   Atsushi Enomoto (atsushi@ximian.com)
+//   Miguel de Icaza (miguel@gnome.org)
+//
+// Copyright (C) 2005, 2010 Novell, Inc (http://www.novell.com)
 //
 // Permission is hereby granted, free of charge, to any person obtaining
 // a copy of this software and associated documentation files (the
@@ -25,6 +54,7 @@
 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 //
 using System;
+using System.Collections.Generic;
 using System.IO;
 using System.Collections.ObjectModel;
 using System.ServiceModel;
@@ -39,26 +69,71 @@ namespace System.ServiceModel.Channels
 
 		public abstract void Clear ();
 
-		[MonoTODO]
 		public static BufferManager CreateBufferManager (
 			long maxBufferPoolSize, int maxBufferSize)
 		{
-			return new DefaultBufferManager (maxBufferPoolSize,
-				maxBufferSize);
+			return new DefaultBufferManager (maxBufferPoolSize, maxBufferSize);
 		}
 
 		public abstract void ReturnBuffer (byte[] buffer);
 
 		public abstract byte[] TakeBuffer (int bufferSize);
 
+#if DEBUG_BUFFER
+		internal abstract void DumpStats ();
+#endif
+		
 		class DefaultBufferManager : BufferManager
 		{
+			const int log_min = 5;   // Anything smaller than 1 << log_cut goes into the first bucket
 			long max_pool_size;
 			int max_size;
-			byte [] buffer;
+			List<byte []> [] buffers = new List<byte []> [32-log_min];
 
-			public DefaultBufferManager (long maxBufferPoolSize,
-				int maxBufferSize)
+#if DEBUG_BUFFER
+			internal override void DumpStats ()
+			{
+				Console.WriteLine ("- hit={0} miss={1}-", hits, miss);
+				for (int i = 0; i < buffers.Length; i++){
+					if (buffers [i] == null)
+						continue;
+					
+					Console.Write ("Slot {0} - {1} [", i, buffers [i].Count);
+					byte [][] arr = buffers [i].ToArray ();
+					
+					for (int j = 0; j < Math.Min (3, arr.Length); j++)
+						Console.Write ("{0} ", arr [j].Length);
+					Console.WriteLine ("]");
+				}
+			}
+#endif
+			
+			static int log2 (uint n)
+			{
+				int pos = 0;
+				if (n >= 1<<16) {
+					n >>= 16;
+					pos += 16;
+				}
+				if (n >= 1<< 8) {
+					n >>=  8;
+					pos +=  8;
+				}
+				if (n >= 1<< 4) {
+					n >>=  4;
+					pos +=  4;
+				}
+				if (n >= 1<< 2) {
+					n >>=  2;
+					pos +=  2;
+				}
+				if (n >= 1<< 1) 
+					pos +=  1;
+
+				return ((n == 0) ? (-1) : pos);
+			}
+			
+			public DefaultBufferManager (long maxBufferPoolSize, int maxBufferSize)
 			{
 				this.max_pool_size = maxBufferPoolSize;
 				this.max_size = maxBufferSize;
@@ -66,28 +141,85 @@ namespace System.ServiceModel.Channels
 
 			public override void Clear ()
 			{
-				if (buffer != null)
-					Array.Clear (buffer, 0, buffer.Length);
+				foreach (var stack in buffers){
+					if (stack == null)
+						continue;
+					stack.Clear ();
+				}
+				Array.Clear (buffers, 0, buffers.Length);
 			}
 
 			public override void ReturnBuffer (byte [] buffer)
 			{
-				// is this correct?
-
-				if (this.buffer == null)
+				if (buffer == null)
 					return;
-				Array.Copy (this.buffer, buffer, this.buffer.Length);
+
+				uint size = (uint) buffer.Length;
+				int l2 = log2 (size);
+				if (l2 > log_min)
+					l2 -= log_min;
+
+				List<byte []> returned = buffers [l2];
+				if (returned == null)
+					returned = buffers [l2] = new List<byte []> ();
+
+				returned.Add (buffer);
 			}
 
+			int hits, miss;
+			
 			public override byte [] TakeBuffer (int bufferSize)
 			{
-				if (bufferSize > max_size)
+				if (bufferSize < 0 || (max_size >= 0 && bufferSize > max_size))
 					throw new ArgumentOutOfRangeException ();
 
-				if (buffer == null || buffer.Length < bufferSize)
-					buffer = new byte [bufferSize];
-				return buffer;
+				int l2 = log2 ((uint) bufferSize);
+				if (l2 > log_min)
+					l2 -= log_min;
+
+				List<byte []> returned = buffers [l2];
+				if (returned == null || returned.Count == 0)
+					return new byte [bufferSize];
+				
+				foreach (var e in returned){
+					if (e.Length >= bufferSize){
+						hits++;
+						returned.Remove (e);
+						return e;
+					}
+				}
+				return new byte [bufferSize];
+			}
+		}
+	}
+
+#if DEBUG_BUFFER
+	class Foo {
+		static void Main ()
+		{
+			var a = BufferManager.CreateBufferManager (1024*1024, 1024*1024);
+			var rand = new Random (0);
+			
+			var buffs = new List<byte []> ();
+			for (int i = 0; i < 4096; i++){
+				a.DumpStats ();
+				var request = rand.Next (1,1024*1024);
+				if ((i % 2) == 0)
+					request = rand.Next (1024, 4096);
+				
+				var x = a.TakeBuffer (request);
+				if (x.Length < request)
+					throw new Exception ();
+				Console.WriteLine ("Delta={2} Requested {0} got={1} bytes ", request, x.Length, x.Length-request);
+				if ((i % 3) == 0){
+					Console.WriteLine ("Return: {0}", x.Length);
+					a.ReturnBuffer (x);
+				}
+				else
+					buffs.Add (x);
 			}
+			a.DumpStats ();
 		}
 	}
-}
+#endif
+}
\ No newline at end of file