Added Write ReadOnlySpan of char override to HttpResponseStreamWriter

Author: alefranz

src/Http/WebUtilities/src/HttpResponseStreamWriter.cs

@@ -127,6 +127,25 @@ public override void Write(char[] values, int index, int count)
             }
         }
 
+        public override void Write(ReadOnlySpan<char> values)
+        {
+            if (_disposed)
+            {
+                throw new ObjectDisposedException(nameof(HttpResponseStreamWriter));
+            }
+
+            bool completed;
+            do
+            {
+                if (_charBufferCount == _charBufferSize)
+                {
+                    FlushInternal(flushEncoder: false);
+                }
+
+                completed = CopyToCharBuffer(ref values);
+            } while (!completed);
+        }
+
         public override void Write(string value)
         {
             if (_disposed)
@@ -423,6 +442,25 @@ private void CopyToCharBuffer(char[] values, ref int index, ref int count)
             count -= remaining;
         }
 
+        private bool CopyToCharBuffer(ref ReadOnlySpan<char> values)
+        {
+            var remaining = Math.Min(_charBufferSize - _charBufferCount, values.Length);
+
+            var source = values.Slice(0, remaining);
+            var destination = new Span<char>(_charBuffer, _charBufferCount, remaining);
+            source.CopyTo(destination);
+
+            _charBufferCount += remaining;
+
+            if (remaining < values.Length)
+            {
+                values = values.Slice(remaining);
+                return false;
+            }
+
+            return true;
+        }
+
         [MethodImpl(MethodImplOptions.NoInlining)]
         private static Task GetObjectDisposedTask()
         {

src/Http/WebUtilities/test/HttpResponseStreamWriterTest.cs

@@ -253,6 +253,29 @@ public void WriteCharArray_WritesToStream(int byteLength)
             Assert.Equal(byteLength, stream.Length);
         }
 
+        [Theory]
+        [InlineData(1023)]
+        [InlineData(1024)]
+        [InlineData(1050)]
+        [InlineData(2048)]
+        public void WriteReadOnlySpanChar_WritesToStream(int byteLength)
+        {
+            // Arrange
+            var stream = new TestMemoryStream();
+            var writer = new HttpResponseStreamWriter(stream, Encoding.UTF8);
+
+            // Act
+            using (writer)
+            {
+                var array = new string('a', byteLength).ToCharArray();
+                var span = new ReadOnlySpan<char>(array);
+                writer.Write(span);
+            }
+
+            // Assert
+            Assert.Equal(byteLength, stream.Length);
+        }
+
         [Theory]
         [InlineData(1023)]
         [InlineData(1024)]