From 007e08ec2ae2c86c11f90218224be2e37adaa572 Mon Sep 17 00:00:00 2001
From: Jan Kotas <jkotas@microsoft.com>
Date: Tue, 20 Feb 2018 08:14:57 -0800
Subject: [PATCH] Replace ValueStringBuilder.set_Length with indexer
 (dotnet/corefx#27274)

Indexer that let's you see and edit the content of the pending string is more efficient and flexible.

Fixes #26643

Signed-off-by: dotnet-bot-corefx-mirror <dotnet-bot@microsoft.com>
---
 .../System/Collections/Generic/ValueListBuilder.cs |  9 +++++++
 .../shared/System/Text/ValueStringBuilder.cs       | 28 +++++++++-------------
 2 files changed, 20 insertions(+), 17 deletions(-)

diff --git a/src/mscorlib/shared/System/Collections/Generic/ValueListBuilder.cs b/src/mscorlib/shared/System/Collections/Generic/ValueListBuilder.cs
index 1bc8ee6..26b3c9f 100644
--- a/src/mscorlib/shared/System/Collections/Generic/ValueListBuilder.cs
+++ b/src/mscorlib/shared/System/Collections/Generic/ValueListBuilder.cs
@@ -23,6 +23,15 @@ namespace System.Collections.Generic
 
         public int Length => _pos;
 
+        public ref T this[int index]
+        {
+            get
+            {
+                Debug.Assert(index < _pos);
+                return ref _span[index];
+            }
+        }
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void Append(T item)
         {
diff --git a/src/mscorlib/shared/System/Text/ValueStringBuilder.cs b/src/mscorlib/shared/System/Text/ValueStringBuilder.cs
index 99045ca..e077a34 100644
--- a/src/mscorlib/shared/System/Text/ValueStringBuilder.cs
+++ b/src/mscorlib/shared/System/Text/ValueStringBuilder.cs
@@ -21,27 +21,21 @@ namespace System.Text
             _pos = 0;
         }
 
-        public int Length
+        public int Length => _pos;
+
+        public ref char this[int index]
         {
-            get => _pos;
-            set
-            {
-                int delta = value - _pos;
-                if (delta > 0)
-                {
-                    Append('\0', delta);
-                }
-                else
-                {
-                    _pos = value;
-                }
+            get
+            {
+                Debug.Assert(index < _pos);
+                return ref _chars[index];
             }
         }
 
         public override string ToString()
         {
             var s = new string(_chars.Slice(0, _pos));
-            Clear();
+            Dispose();
             return s;
         }
 
@@ -50,13 +44,13 @@ namespace System.Text
             if (_chars.Slice(0, _pos).TryCopyTo(destination))
             {
                 charsWritten = _pos;
-                Clear();
+                Dispose();
                 return true;
             }
             else
             {
                 charsWritten = 0;
-                Clear();
+                Dispose();
                 return false;
             }
         }
@@ -185,7 +179,7 @@ namespace System.Text
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private void Clear()
+        public void Dispose()
         {
             char[] toReturn = _arrayToReturnToPool;
             this = default; // for safety, to avoid using pooled array if this instance is erroneously appended to again
-- 
2.7.4