Cache indent strings in CodeWriter

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/CodeGeneration/CodeWriter.IndentCache.cs

@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+
+namespace Microsoft.AspNetCore.Razor.Language.CodeGeneration;
+
+public sealed partial class CodeWriter
+{
+    private static class IndentCache
+    {
+        private static readonly ReadOnlyMemory<char> s_tabs = new string('\t', 64).AsMemory();
+        private static readonly ReadOnlyMemory<char> s_spaces = new string(' ', 128).AsMemory();
+
+        public static ReadOnlyMemory<char> GetIndentString(int size, bool useTabs, int tabSize)
+        {
+            if (!useTabs)
+            {
+                return SliceOrCreate(size, s_spaces);
+            }
+
+            var tabCount = size / tabSize;
+            var spaceCount = size % tabSize;
+
+            if (spaceCount == 0)
+            {
+                return SliceOrCreate(tabCount, s_tabs);
+            }
+
+            return string.Create(length: tabCount + spaceCount, (tabCount, spaceCount), static (destination, state) =>
+            {
+                var (tabCount, spaceCount) = state;
+
+                s_tabs.Span[..tabCount].CopyTo(destination);
+                s_spaces.Span[..spaceCount].CopyTo(destination[tabCount..]);
+            }).AsMemory();
+        }
+
+        private static ReadOnlyMemory<char> SliceOrCreate(int length, ReadOnlyMemory<char> chars)
+        {
+            return (length <= chars.Length)
+                ? chars[..length]
+                : new string(chars.Span[0], length).AsMemory();
+        }
+    }
+}

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/CodeGeneration/CodeWriter.cs

@@ -9,7 +9,6 @@
 using System.IO;
 using System.Runtime.CompilerServices;
 using System.Text;
-using Microsoft.AspNetCore.Razor.PooledObjects;
 using Microsoft.CodeAnalysis.Text;
 
 namespace Microsoft.AspNetCore.Razor.Language.CodeGeneration;
@@ -118,7 +117,7 @@ public int CurrentIndent
             if (_indentSize != value)
             {
                 _indentSize = value;
-                _indentString = ComputeIndent(value, IndentWithTabs, TabSize);
+                _indentString = IndentCache.GetIndentString(value, IndentWithTabs, TabSize);
             }
         }
     }
@@ -189,7 +188,7 @@ public CodeWriter Indent(int size)
 
         var indentString = size == _indentSize
             ? _indentString
-            : ComputeIndent(size, IndentWithTabs, TabSize);
+            : IndentCache.GetIndentString(size, IndentWithTabs, TabSize);
 
         AddTextChunk(indentString);
 
@@ -200,30 +199,6 @@ public CodeWriter Indent(int size)
         return this;
     }
 
-    private static ReadOnlyMemory<char> ComputeIndent(int size, bool useTabs, int tabSize)
-    {
-        if (size == 0)
-        {
-            return ReadOnlyMemory<char>.Empty;
-        }
-
-        if (useTabs)
-        {
-            var tabCount = size / tabSize;
-            var spaceCount = size % tabSize;
-
-            using var _ = StringBuilderPool.GetPooledObject(out var builder);
-            builder.SetCapacityIfLarger(tabCount + spaceCount);
-
-            builder.Append('\t', tabCount);
-            builder.Append(' ', spaceCount);
-
-            return builder.ToString().AsMemory();
-        }
-
-        return new string(' ', size).AsMemory();
-    }
-
     public CodeWriter Write(string value)
     {
         ArgHelper.ThrowIfNull(value);