Initial rough changes to reduce heap allocations

LibuvSharp.diff

 LibuvSharp/ByteBufferAllocatorBase.cs       |  2 ++
 LibuvSharp/Common.cs                        | 16 ++++++----
 LibuvSharp/CopyingByteBufferAllocator.cs    |  6 +---
 LibuvSharp/Internal/BufferPin.cs            |  4 ++-
 LibuvSharp/Internal/CallbackPermaRequest.cs |  5 ++-
 LibuvSharp/LibuvSharp.net3.5.csproj         |  9 +++++-
 LibuvSharp/UVStream.cs                      | 39 +++++++++++++----------
 LibuvSharp/UVTimer.cs                       | 48 +++++++++++++----------------
 8 files changed, 73 insertions(+), 56 deletions(-)

diff --git a/LibuvSharp/ByteBufferAllocatorBase.cs b/LibuvSharp/ByteBufferAllocatorBase.cs
index 47af9b4..64e59d2 100644
--- a/LibuvSharp/ByteBufferAllocatorBase.cs
+++ b/LibuvSharp/ByteBufferAllocatorBase.cs
@@ -8,6 +8,8 @@ namespace LibuvSharp
 		internal Handle.alloc_callback_unix AllocCallbackUnix { get; set; }
 		internal Handle.alloc_callback_win AllocCallbackWin { get; set; }
 
+		public virtual byte[] Buffer => null;
+
 		public ByteBufferAllocatorBase()
 		{
 			AllocCallbackUnix = AllocUnix;
diff --git a/LibuvSharp/Common.cs b/LibuvSharp/Common.cs
index b7ddb14..03b72e0 100644
--- a/LibuvSharp/Common.cs
+++ b/LibuvSharp/Common.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Buffers;
 using System.Net;
 using System.Runtime.InteropServices;
 using System.Collections.Generic;
@@ -101,17 +102,20 @@ namespace LibuvSharp
 
 		unsafe internal static IPEndPoint GetIPEndPoint(IntPtr sockaddr, bool map)
 		{
-			sockaddr *sa = (sockaddr *)sockaddr;
-			byte[] addr = new byte[64];
+			sockaddr* sa = (sockaddr*)sockaddr;
+			byte[] addr = ArrayPool<byte>.Shared.Rent(64);
+
 			int r;
-			if (sa->sin_family == 2) {
+			if (sa->sin_family == 2)
 				r = uv_ip4_name(sockaddr, addr, (IntPtr)addr.Length);
-			} else {
+			else
 				r = uv_ip6_name(sockaddr, addr, (IntPtr)addr.Length);
-			}
+
 			Ensure.Success(r);
 
-			IPAddress ip = IPAddress.Parse(System.Text.Encoding.ASCII.GetString(addr, 0, strlen(addr)));
+			IPAddress ip = new IPAddress(addr);
+
+			ArrayPool<byte>.Shared.Return(addr, true);
 
 			var bytes = ip.GetAddressBytes();
 			if (map && ip.AddressFamily == System.Net.Sockets.AddressFamily.InterNetworkV6 && IsMapping(bytes)) {
diff --git a/LibuvSharp/CopyingByteBufferAllocator.cs b/LibuvSharp/CopyingByteBufferAllocator.cs
index f78896b..d4557da 100644
--- a/LibuvSharp/CopyingByteBufferAllocator.cs
+++ b/LibuvSharp/CopyingByteBufferAllocator.cs
@@ -7,11 +7,7 @@ namespace LibuvSharp
 	{
 		BufferPin pin;
 
-		public byte[] Buffer {
-			get {
-				return pin.Buffer;
-			}
-		}
+		public override byte[] Buffer => pin.Buffer;
 
 		public override int Alloc(int size, out IntPtr ptr)
 		{
diff --git a/LibuvSharp/Internal/BufferPin.cs b/LibuvSharp/Internal/BufferPin.cs
index 7ac7b62..aa76796 100644
--- a/LibuvSharp/Internal/BufferPin.cs
+++ b/LibuvSharp/Internal/BufferPin.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Buffers;
 using System.Runtime.InteropServices;
 
 namespace LibuvSharp
@@ -9,7 +10,7 @@ namespace LibuvSharp
 		public GCHandle GCHandle { get; protected set; }
 
 		public BufferPin(int count)
-			: this(new byte[count])
+			: this(ArrayPool<byte>.Shared.Rent(count))
 		{
 		}
 
@@ -59,6 +60,7 @@ namespace LibuvSharp
 				GCHandle.Free();
 			}
 			Pointer = IntPtr.Zero;
+			ArrayPool<byte>.Shared.Return(Buffer, true);
 		}
 
 		public IntPtr Pointer { get; protected set; }
diff --git a/LibuvSharp/Internal/CallbackPermaRequest.cs b/LibuvSharp/Internal/CallbackPermaRequest.cs
index 339b85d..e59bdb9 100644
--- a/LibuvSharp/Internal/CallbackPermaRequest.cs
+++ b/LibuvSharp/Internal/CallbackPermaRequest.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Runtime.InteropServices;
 
 namespace LibuvSharp
 {
@@ -14,7 +15,9 @@ namespace LibuvSharp
 		{
 		}
 
-		public Action<int, CallbackPermaRequest> Callback { get; set; }
+		public Action<int, CallbackPermaRequest> Callback;
+		public GCHandle GcHandle;
+		public Action<Exception> WriteCallback;
 
 		protected void End(IntPtr ptr, int status)
 		{
diff --git a/LibuvSharp/LibuvSharp.net3.5.csproj b/LibuvSharp/LibuvSharp.net3.5.csproj
index ac98b59..fa4fc9a 100644
--- a/LibuvSharp/LibuvSharp.net3.5.csproj
+++ b/LibuvSharp/LibuvSharp.net3.5.csproj
@@ -36,11 +36,14 @@
     <Reference Include="System" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="ArrayPool.cs" />
     <Compile Include="AssemblyInfo.cs" />
     <Compile Include="AsyncCallback.cs" />
     <Compile Include="AsyncWatcher.cs" />
     <Compile Include="CallbackHandle.cs" />
     <Compile Include="Common.cs" />
+    <Compile Include="DefaultArrayPool.cs" />
+    <Compile Include="DefaultArrayPoolBucket.cs" />
     <Compile Include="Handle.cs" />
     <Compile Include="HandleBase.cs" />
     <Compile Include="IBindable.cs" />
@@ -65,9 +68,13 @@
     <Compile Include="ITrySendExtensions.cs" />
     <Compile Include="ITryWrite.cs" />
     <Compile Include="ITryWriteExtensions.cs" />
+    <Compile Include="Platform.cs" />
+    <Compile Include="PlatformHelper.cs" />
     <Compile Include="Prepare.cs" />
     <Compile Include="Loop.cs" />
     <Compile Include="net35/Tuple.cs" />
+    <Compile Include="Spinlock.cs" />
+    <Compile Include="Spinwait.cs" />
     <Compile Include="Udp.cs" />
     <Compile Include="Tcp.cs" />
     <Compile Include="Exceptions.cs" />
@@ -125,4 +132,4 @@
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <ItemGroup />
-</Project>
+</Project>
\ No newline at end of file
diff --git a/LibuvSharp/UVStream.cs b/LibuvSharp/UVStream.cs
index ba36fa6..0b6c995 100644
--- a/LibuvSharp/UVStream.cs
+++ b/LibuvSharp/UVStream.cs
@@ -58,6 +58,7 @@ namespace LibuvSharp
 			: base(loop, handle)
 		{
 			stream = (uv_stream_t *)(handle.ToInt64() + Handle.Size(HandleType.UV_HANDLE));
+			writeCallback = WriteCallback;
 		}
 
 		internal UVStream(Loop loop, int size)
@@ -133,7 +134,7 @@ namespace LibuvSharp
 					Close();
 				}
 			} else {
-				OnData(ByteBufferAllocator.Retrieve(size.ToInt32()));
+				OnData(new ArraySegment<byte>(ByteBufferAllocator.Buffer, 0, (int)nread));
 			}
 		}
 
@@ -182,35 +183,41 @@ namespace LibuvSharp
 
 			PendingWrites++;
 
-			GCHandle datagchandle = GCHandle.Alloc(data.Array, GCHandleType.Pinned);
-			CallbackPermaRequest cpr = new CallbackPermaRequest(RequestType.UV_WRITE);
-			cpr.Callback = (status, cpr2) => {
-				datagchandle.Free();
-				PendingWrites--;
+			var datagchandle = GCHandle.Alloc(data.Array, GCHandleType.Pinned);
 
-				Ensure.Success(status, callback);
-
-				if (PendingWrites == 0) {
-					OnDrain();
-				}
-			};
+			var cpr = new CallbackPermaRequest(RequestType.UV_WRITE); //TODO: pool and reuse requests
+			cpr.Callback = writeCallback;
+			cpr.WriteCallback = callback;
+			cpr.GcHandle = datagchandle;
 
 			var ptr = (IntPtr)(datagchandle.AddrOfPinnedObject().ToInt64() + index);
 
 			int r;
 			if (UV.isUnix) {
-				UnixBufferStruct[] buf = new UnixBufferStruct[1];
-				buf[0] = new UnixBufferStruct(ptr, count);
+				UnixBufferStruct[] buf = { new UnixBufferStruct(ptr, count) };
 				r = uv_write_unix(cpr.Handle, NativeHandle, buf, 1, CallbackPermaRequest.CallbackDelegate);
 			} else {
-				WindowsBufferStruct[] buf = new WindowsBufferStruct[1];
-				buf[0] = new WindowsBufferStruct(ptr, count);
+				WindowsBufferStruct[] buf = { new WindowsBufferStruct(ptr, count) };
 				r = uv_write_win(cpr.Handle, NativeHandle, buf, 1, CallbackPermaRequest.CallbackDelegate);
 			}
 
 			Ensure.Success(r);
 		}
 
+		private Action<int, CallbackPermaRequest> writeCallback;
+		void WriteCallback(int status, CallbackPermaRequest cpr)
+		{
+			cpr.GcHandle.Free();
+			var pending_writes = --PendingWrites;
+
+			Ensure.Success(status, cpr.WriteCallback);
+
+			if (pending_writes == 0)
+			{
+				OnDrain();
+			}
+		}
+		
 		public void Shutdown(Action<Exception> callback)
 		{
 			CheckDisposed();
diff --git a/LibuvSharp/UVTimer.cs b/LibuvSharp/UVTimer.cs
index ee7e70a..a17f1e1 100644
--- a/LibuvSharp/UVTimer.cs
+++ b/LibuvSharp/UVTimer.cs
@@ -25,14 +25,21 @@ namespace LibuvSharp
 
 		Action onehit;
 
+		Action callback;
+		Action<int> callback1;
+
+		int iterations;
+		int totalIterations;
+
 		public UVTimer()
-			: this(Loop.Constructor)
+			: this(Loop.Constructor, 1)
 		{
 		}
 
-		public UVTimer(Loop loop)
+		public UVTimer(Loop loop, int iteration_count)
 			: base(loop, HandleType.UV_TIMER, uv_timer_init)
 		{
+			totalIterations = iteration_count;
 		}
 
 		public ulong LongRepeat {
@@ -87,13 +94,16 @@ namespace LibuvSharp
 				cb();
 			}
 
-			if (Tick != null) {
-				Tick();
+			if (callback1 != null) {
+				var i = ++iterations;
+				callback1(i);
+				if (i >= totalIterations) Close();
+			} else {
+				callback?.Invoke();
+				if (totalIterations > 0) Close();
 			}
 		}
 
-		public event Action Tick;
-
 		public void Start(ulong repeat)
 		{
 			Start(0, repeat);
@@ -135,13 +145,8 @@ namespace LibuvSharp
 
 		public static UVTimer Once(Loop loop, TimeSpan timeout, Action callback)
 		{
-			var timer = new UVTimer(loop);
-			timer.Tick += () => {
-				if (callback != null) {
-					callback();
-				}
-				timer.Close();
-			};
+			var timer = new UVTimer(loop, 1);
+			timer.callback = callback;
 			timer.Start(timeout, TimeSpan.Zero);
 			return timer;
 		}
@@ -153,17 +158,8 @@ namespace LibuvSharp
 
 		public static UVTimer Times(Loop loop, int times, TimeSpan repeat, Action<int> callback)
 		{
-			var timer = new UVTimer(loop);
-			int i = 0;
-			timer.Tick += () => {
-				i++;
-				if (callback != null) {
-					callback(i);
-				}
-				if (i >= times) {
-					timer.Close();
-				}
-			};
+			var timer = new UVTimer(loop, times);
+			timer.callback1 = callback;
 			timer.Start(repeat, repeat);
 			return timer;
 		}
@@ -175,8 +171,8 @@ namespace LibuvSharp
 
 		public static UVTimer Every(Loop loop, TimeSpan repeat, Action callback)
 		{
-			var timer = new UVTimer(loop);
-			timer.Tick += callback;
+			var timer = new UVTimer(loop, 0);
+			timer.callback = callback;
 			timer.Start(repeat, repeat);
 			return timer;
 		}