From b0fb3fa764cd644594d452565f6e0f994e731b30 Mon Sep 17 00:00:00 2001
From: Justin Van Patten <jvp@justinvp.com>
Date: Mon, 11 May 2015 00:03:34 -0700
Subject: [PATCH] Avoid unnecessary delegate allocations

There are 9 up-front delegate allocations (2 for TextReader and 7 for
TextWriter) that are unnecessary in most cases as most
TextReader/TextWriter subclasses override the base async methods where
such delegates are used. Instead, let the compiler allocate and cache
such delegates lazily, only in the rare cases when the delegates are
actually used.
---
 src/mscorlib/src/System/IO/TextReader.cs |  25 ++++----
 src/mscorlib/src/System/IO/TextWriter.cs | 105 ++++++++++++++-----------------
 2 files changed, 59 insertions(+), 71 deletions(-)

diff --git a/src/mscorlib/src/System/IO/TextReader.cs b/src/mscorlib/src/System/IO/TextReader.cs
index 98a6c8a..448bcbc 100644
--- a/src/mscorlib/src/System/IO/TextReader.cs
+++ b/src/mscorlib/src/System/IO/TextReader.cs
@@ -40,16 +40,6 @@ namespace System.IO {
     public abstract class TextReader : IDisposable {
 #endif // FEATURE_REMOTING
 
-        [NonSerialized]
-        private static Func<object, string> _ReadLineDelegate = state => ((TextReader)state).ReadLine();
-
-        [NonSerialized]
-        private static Func<object, int> _ReadDelegate = state => 
-        {
-            Tuple<TextReader, char[], int, int> tuple = (Tuple<TextReader, char[], int, int>)state;
-            return tuple.Item1.Read(tuple.Item2, tuple.Item3, tuple.Item4);
-        };
-
         public static readonly TextReader Null = new NullTextReader();
     
         protected TextReader() {}
@@ -189,7 +179,11 @@ namespace System.IO {
         [ComVisible(false)]
         public virtual Task<String> ReadLineAsync()
         {
-            return Task<String>.Factory.StartNew(_ReadLineDelegate, this, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+            return Task<String>.Factory.StartNew(state =>
+            {
+                return ((TextReader)state).ReadLine();
+            },
+            this, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
         }
 
         [HostProtection(ExternalThreading=true)]
@@ -228,8 +222,13 @@ namespace System.IO {
             Contract.Requires(count >= 0);
             Contract.Requires(buffer.Length - index >= count);
 
-            Tuple<TextReader, char[], int, int> tuple = new Tuple<TextReader, char[], int, int>(this, buffer, index, count);
-            return Task<int>.Factory.StartNew(_ReadDelegate, tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+            var tuple = new Tuple<TextReader, char[], int, int>(this, buffer, index, count);
+            return Task<int>.Factory.StartNew(state =>
+            {
+                var t = (Tuple<TextReader, char[], int, int>)state;
+                return t.Item1.Read(t.Item2, t.Item3, t.Item4);
+            },
+            tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
         }
 
         [HostProtection(ExternalThreading=true)]
diff --git a/src/mscorlib/src/System/IO/TextWriter.cs b/src/mscorlib/src/System/IO/TextWriter.cs
index 4203fa9..71d39a2 100644
--- a/src/mscorlib/src/System/IO/TextWriter.cs
+++ b/src/mscorlib/src/System/IO/TextWriter.cs
@@ -41,51 +41,6 @@ namespace System.IO {
 #endif // FEATURE_REMOTING
         public static readonly TextWriter Null = new NullTextWriter();
 
-        [NonSerialized]
-        private static Action<object> _WriteCharDelegate = state =>
-        {
-            Tuple<TextWriter, char> tuple = (Tuple<TextWriter, char>)state;
-            tuple.Item1.Write(tuple.Item2);
-        };
-
-        [NonSerialized]
-        private static Action<object> _WriteStringDelegate = state =>
-        {
-            Tuple<TextWriter, string> tuple = (Tuple<TextWriter, string>)state;
-            tuple.Item1.Write(tuple.Item2);
-        };
-
-        [NonSerialized]
-        private static Action<object> _WriteCharArrayRangeDelegate = state =>
-        {
-            Tuple<TextWriter, char[], int, int> tuple = (Tuple<TextWriter, char[],int, int>)state;
-            tuple.Item1.Write(tuple.Item2, tuple.Item3, tuple.Item4);
-        };
-
-        [NonSerialized]
-        private static Action<object> _WriteLineCharDelegate = state =>
-        {
-            Tuple<TextWriter, char> tuple = (Tuple<TextWriter, char>)state;
-            tuple.Item1.WriteLine(tuple.Item2);
-        };
-
-        [NonSerialized]
-        private static Action<object> _WriteLineStringDelegate = state =>
-        {
-            Tuple<TextWriter, string> tuple = (Tuple<TextWriter, string>)state;
-            tuple.Item1.WriteLine(tuple.Item2);
-        };
-
-        [NonSerialized]
-        private static Action<object> _WriteLineCharArrayRangeDelegate = state =>
-        {
-            Tuple<TextWriter, char[], int, int> tuple = (Tuple<TextWriter, char[],int, int>)state;
-            tuple.Item1.WriteLine(tuple.Item2, tuple.Item3, tuple.Item4);
-        };
-
-        [NonSerialized]
-        private static Action<object> _FlushDelegate = state => ((TextWriter)state).Flush();
-
         // This should be initialized to Environment.NewLine, but
         // to avoid loading Environment unnecessarily so I've duplicated
         // the value here.
@@ -538,16 +493,26 @@ namespace System.IO {
         [ComVisible(false)]
         public virtual Task WriteAsync(char value)
         {
-            Tuple<TextWriter, char> tuple = new Tuple<TextWriter, char>(this, value);
-            return Task.Factory.StartNew(_WriteCharDelegate, tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+            var tuple = new Tuple<TextWriter, char>(this, value);
+            return Task.Factory.StartNew(state =>
+            {
+                var t = (Tuple<TextWriter, char>)state;
+                t.Item1.Write(t.Item2);
+            },
+            tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
         }
 
         [HostProtection(ExternalThreading = true)]
         [ComVisible(false)]
         public virtual Task WriteAsync(String value)
         {
-            Tuple<TextWriter, string> tuple = new Tuple<TextWriter, string>(this, value);
-            return Task.Factory.StartNew(_WriteStringDelegate, tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+            var tuple = new Tuple<TextWriter, string>(this, value);
+            return Task.Factory.StartNew(state =>
+            {
+                var t = (Tuple<TextWriter, string>)state;
+                t.Item1.Write(t.Item2);
+            },
+            tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
         }
 
         [HostProtection(ExternalThreading = true)]
@@ -562,24 +527,39 @@ namespace System.IO {
         [ComVisible(false)]
         public virtual Task WriteAsync(char[] buffer, int index, int count)
         {
-            Tuple<TextWriter, char[], int, int> tuple = new Tuple<TextWriter, char[], int, int>(this, buffer, index, count);
-            return Task.Factory.StartNew(_WriteCharArrayRangeDelegate, tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+            var tuple = new Tuple<TextWriter, char[], int, int>(this, buffer, index, count);
+            return Task.Factory.StartNew(state =>
+            {
+                var t = (Tuple<TextWriter, char[], int, int>)state;
+                t.Item1.Write(t.Item2, t.Item3, t.Item4);
+            },
+            tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
         }
 
         [HostProtection(ExternalThreading = true)]
         [ComVisible(false)]
         public virtual Task WriteLineAsync(char value)
         {
-            Tuple<TextWriter, char> tuple = new Tuple<TextWriter, char>(this, value);
-            return Task.Factory.StartNew(_WriteLineCharDelegate, tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+            var tuple = new Tuple<TextWriter, char>(this, value);
+            return Task.Factory.StartNew(state =>
+            {
+                var t = (Tuple<TextWriter, char>)state;
+                t.Item1.WriteLine(t.Item2);
+            },
+            tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
         }
 
         [HostProtection(ExternalThreading = true)]
         [ComVisible(false)]
         public virtual Task WriteLineAsync(String value)
         {
-            Tuple<TextWriter, string> tuple = new Tuple<TextWriter, string>(this, value);
-            return Task.Factory.StartNew(_WriteLineStringDelegate, tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+            var tuple = new Tuple<TextWriter, string>(this, value);
+            return Task.Factory.StartNew(state =>
+            {
+                var t = (Tuple<TextWriter, string>)state;
+                t.Item1.WriteLine(t.Item2);
+            },
+            tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
         }
 
         [HostProtection(ExternalThreading = true)]
@@ -594,8 +574,13 @@ namespace System.IO {
         [ComVisible(false)]
         public virtual Task WriteLineAsync(char[] buffer, int index, int count)
         {
-            Tuple<TextWriter, char[], int, int> tuple = new Tuple<TextWriter, char[], int, int>(this, buffer, index, count);
-            return Task.Factory.StartNew(_WriteLineCharArrayRangeDelegate, tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+            var tuple = new Tuple<TextWriter, char[], int, int>(this, buffer, index, count);
+            return Task.Factory.StartNew(state =>
+            {
+                var t = (Tuple<TextWriter, char[], int, int>)state;
+                t.Item1.WriteLine(t.Item2, t.Item3, t.Item4);
+            },
+            tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
         }
 
         [HostProtection(ExternalThreading = true)]
@@ -609,7 +594,11 @@ namespace System.IO {
         [ComVisible(false)]
         public virtual Task FlushAsync()
         {
-            return Task.Factory.StartNew(_FlushDelegate, this, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+            return Task.Factory.StartNew(state =>
+            {
+                ((TextWriter)state).Flush();
+            },
+            this, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
         }
         #endregion
 
-- 
2.7.4