Using stackalloc instead of new byte[x] on Streams

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/DecompressionHandler.cs

@@ -395,7 +395,7 @@ public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken
                         }
 
                         Debug.Assert(_firstByteStatus == FirstByteStatus.Consumed);
-                        return _stream.ReadAsync(buffer, cancellationToken);
+                        return _stream.ReadAsync(buffer, cancellationToken).ConfigureAwait(false);
                     }
 
                     public override async Task CopyToAsync(Stream destination, int bufferSize, CancellationToken cancellationToken)

src/libraries/System.Net.Security/src/System/Net/Security/SslStream.cs

@@ -740,12 +740,10 @@ public override int ReadByte()
             }
 
             // Otherwise, fall back to reading a byte via Read, the same way Stream.ReadByte does.
-            // This allocation is unfortunate but should be relatively rare, as it'll only occur once
-            // per buffer fill internally by Read.
-            byte[] oneByte = new byte[1];
-            int bytesRead = Read(oneByte, 0, 1);
+            Span<byte> oneByteSpan = stackalloc byte[1];
+            int bytesRead = Read(oneByteSpan);
             Debug.Assert(bytesRead == 0 || bytesRead == 1);
-            return bytesRead == 1 ? oneByte[0] : -1;
+            return bytesRead == 1 ? oneByteSpan[0] : -1;
         }
 
         public override int Read(byte[] buffer, int offset, int count)

src/libraries/System.Private.CoreLib/src/System/IO/Stream.cs

@@ -809,9 +809,9 @@ public virtual int Read(Span<byte> buffer)
 
         public virtual int ReadByte()
         {
-            var oneByteArray = new byte[1];
-            int r = Read(oneByteArray, 0, 1);
-            return r == 0 ? -1 : oneByteArray[0];
+            Span<byte> oneByteSpan = stackalloc byte[1];
+            int r = Read(oneByteSpan);
+            return r == 0 ? -1 : oneByteSpan[0];
         }
 
         /// <summary>
@@ -933,7 +933,7 @@ public virtual void Write(ReadOnlySpan<byte> buffer)
             }
         }
 
-        public virtual void WriteByte(byte value) => Write(new byte[1] { value }, 0, 1);
+        public virtual void WriteByte(byte value) => Write(stackalloc byte[1] { value });
 
         public static Stream Synchronized(Stream stream)
         {

src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/Json/JsonEncodingStreamWrapper.cs

@@ -16,7 +16,6 @@ internal sealed class JsonEncodingStreamWrapper : Stream
     {
         private const int BufferLength = 128;
 
-        private readonly byte[] _byteBuffer = new byte[1];
         private int _byteCount;
         private int _byteOffset;
         private byte[]? _bytes;
@@ -227,11 +226,12 @@ public override int ReadByte()
             {
                 return _stream.ReadByte();
             }
-            if (Read(_byteBuffer, 0, 1) == 0)
+            Span<byte> oneByteSpan = stackalloc byte[1];
+            if (Read(oneByteSpan) == 0)
             {
                 return -1;
             }
-            return _byteBuffer[0];
+            return oneByteSpan[0];
         }
 
         public override long Seek(long offset, SeekOrigin origin)
@@ -274,8 +274,7 @@ public override void WriteByte(byte b)
                 _stream.WriteByte(b);
                 return;
             }
-            _byteBuffer[0] = b;
-            Write(_byteBuffer, 0, 1);
+            Write(stackalloc byte[1] {b});
         }
 
         private static Encoding GetEncoding(SupportedEncoding e) =>