Optimize large buffer allocations with ArrayPool

PolyShim/Net50/Convert.cs

@@ -6,6 +6,7 @@
 // ReSharper disable PartialTypeWithSinglePart
 
 using System;
+using System.Buffers;
 using System.Diagnostics.CodeAnalysis;
 
 [ExcludeFromCodeCoverage]
@@ -48,17 +49,23 @@ static int GetHexValue(char c)
         // https://learn.microsoft.com/dotnet/api/system.convert.tohexstring#system-convert-tohexstring(system-byte()-system-int32-system-int32)
         public static string ToHexString(byte[] value, int startIndex, int length)
         {
-            var c = new char[length * 2];
+            var chars = ArrayPool<char>.Shared.Rent(length * 2);
+            try
+            {
+                for (var i = 0; i < length; i++)
+                {
+                    var b = value[startIndex + i] >> 4;
+                    chars[i * 2] = (char)(55 + b + (((b - 10) >> 31) & -7));
+                    b = value[startIndex + i] & 0xF;
+                    chars[i * 2 + 1] = (char)(55 + b + (((b - 10) >> 31) & -7));
+                }
 
-            for (var i = 0; i < length; i++)
+                return new string(chars, 0, length * 2);
+            }
+            finally
             {
-                var b = value[startIndex + i] >> 4;
-                c[i * 2] = (char)(55 + b + (((b - 10) >> 31) & -7));
-                b = value[startIndex + i] & 0xF;
-                c[i * 2 + 1] = (char)(55 + b + (((b - 10) >> 31) & -7));
+                ArrayPool<char>.Shared.Return(chars);
             }
-
-            return new string(c);
         }
 
         // https://learn.microsoft.com/dotnet/api/system.convert.tohexstring#system-convert-tohexstring(system-byte())

PolyShim/Net70/TextReader.cs

@@ -6,6 +6,7 @@
 // ReSharper disable PartialTypeWithSinglePart
 
 using System;
+using System.Buffers;
 using System.IO;
 using System.Text;
 using System.Threading;
@@ -30,21 +31,28 @@ internal static class MemberPolyfills_Net70_TextReader
         public async Task<string> ReadToEndAsync(CancellationToken cancellationToken)
         {
             var result = new StringBuilder();
-            var buffer = new char[4096];
-
-            while (true)
+            var buffer = ArrayPool<char>.Shared.Rent(4096);
+            try
             {
-                var charsRead = await reader
-                    .ReadAsync(buffer, cancellationToken)
-                    .ConfigureAwait(false);
+                while (true)
+                {
+                    var charsRead = await reader
+                        .ReadAsync(buffer, 0, buffer.Length)
+                        .ConfigureAwait(false);
 
-                if (charsRead <= 0)
-                    break;
+                    if (charsRead <= 0)
+                        break;
 
-                result.Append(buffer, 0, charsRead);
-            }
+                    cancellationToken.ThrowIfCancellationRequested();
+                    result.Append(buffer, 0, charsRead);
+                }
 
-            return result.ToString();
+                return result.ToString();
+            }
+            finally
+            {
+                ArrayPool<char>.Shared.Return(buffer);
+            }
         }
 #endif
     }

PolyShim/Net80/RandomNumberGenerator.cs

@@ -6,6 +6,7 @@
 // ReSharper disable PartialTypeWithSinglePart
 
 using System;
+using System.Buffers;
 using System.Text;
 using System.Diagnostics.CodeAnalysis;
 using System.Security.Cryptography;
@@ -46,11 +47,21 @@ public static void Shuffle<T>(Span<T> items)
         // https://learn.microsoft.com/dotnet/api/system.security.cryptography.randomnumbergenerator.gethexstring#system-security-cryptography-randomnumbergenerator-gethexstring(system-int32-system-boolean)
         public static string GetHexString(int stringLength, bool lowercase = false)
         {
-            var bytes = new byte[(stringLength + 1) / 2];
-            RandomNumberGenerator.Fill(bytes);
+            var byteCount = (stringLength + 1) / 2;
+            var bytes = ArrayPool<byte>.Shared.Rent(byteCount);
+            try
+            {
+                RandomNumberGenerator.Fill(bytes.AsSpan(0, byteCount));
 
-            var hex = lowercase ? Convert.ToHexStringLower(bytes) : Convert.ToHexString(bytes);
-            return hex.Substring(0, stringLength);
+                var hex = lowercase
+                    ? Convert.ToHexStringLower(bytes, 0, byteCount)
+                    : Convert.ToHexString(bytes, 0, byteCount);
+                return hex.Substring(0, stringLength);
+            }
+            finally
+            {
+                ArrayPool<byte>.Shared.Return(bytes, clearArray: true);
+            }
         }
 
         // https://learn.microsoft.com/dotnet/api/system.security.cryptography.randomnumbergenerator.getstring

PolyShim/NetCore10/Stream.cs

@@ -5,6 +5,7 @@
 // ReSharper disable InconsistentNaming
 // ReSharper disable PartialTypeWithSinglePart
 
+using System.Buffers;
 using System.IO;
 using System.Diagnostics.CodeAnalysis;
 
@@ -16,14 +17,21 @@ internal static class MemberPolyfills_NetCore10_Stream
         // https://learn.microsoft.com/dotnet/api/system.io.stream.copyto#system-io-stream-copyto(system-io-stream-system-int32)
         public void CopyTo(Stream destination, int bufferSize)
         {
-            var buffer = new byte[bufferSize];
-            while (true)
+            var buffer = ArrayPool<byte>.Shared.Rent(bufferSize);
+            try
             {
-                var bytesRead = source.Read(buffer, 0, buffer.Length);
-                if (bytesRead <= 0)
-                    break;
+                while (true)
+                {
+                    var bytesRead = source.Read(buffer, 0, buffer.Length);
+                    if (bytesRead <= 0)
+                        break;
 
-                destination.Write(buffer, 0, bytesRead);
+                    destination.Write(buffer, 0, bytesRead);
+                }
+            }
+            finally
+            {
+                ArrayPool<byte>.Shared.Return(buffer);
             }
         }
 

PolyShim/NetCore20/File.cs

@@ -5,6 +5,7 @@
 // ReSharper disable InconsistentNaming
 // ReSharper disable PartialTypeWithSinglePart
 
+using System.Buffers;
 using System.Collections.Generic;
 using System.IO;
 using System.Text;
@@ -130,43 +131,57 @@ public static async Task<string[]> ReadAllLinesAsync(string path, Encoding encod
         // https://learn.microsoft.com/dotnet/api/system.io.file.readalltextasync#system-io-file-readalltextasync(system-string-system-threading-cancellationtoken)
         public static async Task<string> ReadAllTextAsync(string path, CancellationToken cancellationToken = default)
         {
-            using var stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read, 4096, true);
+            const int bufferSize = 4096;
+            using var stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read, bufferSize, true);
             using var reader = new StreamReader(stream);
 
             var content = new StringBuilder();
-            var buffer = new char[4096];
+            var buffer = ArrayPool<char>.Shared.Rent(bufferSize);
+            try
+            {
+                cancellationToken.ThrowIfCancellationRequested();
 
-            cancellationToken.ThrowIfCancellationRequested();
+                int charsRead;
+                while ((charsRead = await reader.ReadAsync(buffer, 0, buffer.Length).ConfigureAwait(false)) > 0)
+                {
+                    cancellationToken.ThrowIfCancellationRequested();
+                    content.Append(buffer, 0, charsRead);
+                }
 
-            int charsRead;
-            while ((charsRead = await reader.ReadAsync(buffer, 0, buffer.Length).ConfigureAwait(false)) > 0)
+                return content.ToString();
+            }
+            finally
             {
-                cancellationToken.ThrowIfCancellationRequested();
-                content.Append(buffer, 0, charsRead);
+                ArrayPool<char>.Shared.Return(buffer);
             }
-
-            return content.ToString();
         }
 
         // https://learn.microsoft.com/dotnet/api/system.io.file.readalltextasync#system-io-file-readalltextasync(system-string-system-text-encoding-system-threading-cancellationtoken)
         public static async Task<string> ReadAllTextAsync(string path, Encoding encoding, CancellationToken cancellationToken = default)
         {
-            using var stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read, 4096, true);
+            const int bufferSize = 4096;
+            using var stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read, bufferSize, true);
             using var reader = new StreamReader(stream, encoding);
 
             var content = new StringBuilder();
-            var buffer = new char[4096];
+            var buffer = ArrayPool<char>.Shared.Rent(bufferSize);
+            try
+            {
+                cancellationToken.ThrowIfCancellationRequested();
 
-            cancellationToken.ThrowIfCancellationRequested();
+                int charsRead;
+                while ((charsRead = await reader.ReadAsync(buffer, 0, buffer.Length).ConfigureAwait(false)) > 0)
+                {
+                    cancellationToken.ThrowIfCancellationRequested();
+                    content.Append(buffer, 0, charsRead);
+                }
 
-            int charsRead;
-            while ((charsRead = await reader.ReadAsync(buffer, 0, buffer.Length).ConfigureAwait(false)) > 0)
+                return content.ToString();
+            }
+            finally
             {
-                cancellationToken.ThrowIfCancellationRequested();
-                content.Append(buffer, 0, charsRead);
+                ArrayPool<char>.Shared.Return(buffer);
             }
-
-            return content.ToString();
         }
 
         // https://learn.microsoft.com/dotnet/api/system.io.file.writeallbytesasync#system-io-file-writeallbytesasync(system-string-system-byte()-system-threading-cancellationtoken)