CoreFx #22409 StreamWriter Span based API and tests

src/System.IO/tests/StreamWriter/StreamWriter.WriteTests.netcoreapp.cs

@@ -0,0 +1,54 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Xunit;
+
+namespace System.IO.Tests
+{
+    public partial class WriteTests
+    {
+        [Fact]
+        public void WriteReadOnlySpanTest()
+        {
+            char[] chArr = setupArray();
+            ReadOnlySpan<char> readSpan = new ReadOnlySpan<char>(chArr);
+
+            Stream ms = CreateStream();
+            StreamWriter sw = new StreamWriter(ms);
+            StreamReader sr;
+
+            sw.Write(readSpan);
+            sw.Flush();
+            ms.Position = 0;
+            sr = new StreamReader(ms);
+
+            for (int i = 0; i < chArr.Length; i++)
+            {
+                Assert.Equal((int)chArr[i], sr.Read());
+            }
+            ms.Dispose();
+        }
+
+        [Fact]
+        public void WriteLineReadOnlySpanTest()
+        {
+            char[] chArr = setupArray();
+            ReadOnlySpan<char> readSpan = new ReadOnlySpan<char>(chArr);
+
+            Stream ms = CreateStream();
+            StreamWriter sw = new StreamWriter(ms);
+            StreamReader sr;
+
+            sw.Write(readSpan);
+            sw.Flush();
+            ms.Position = 0;
+            sr = new StreamReader(ms);
+
+            string readData = sr.ReadLine();
+            Assert.Equal(new string(chArr), readData);
+
+            ms.Dispose();
+        }
+    }
+}

src/System.IO/tests/System.IO.Tests.csproj

@@ -15,6 +15,7 @@
     <Compile Include="IndentedTextWriter.cs" />
     <Compile Include="BinaryReader\BinaryReaderTests.cs" />
     <Compile Include="MemoryStream\MemoryStream.GetBufferTests.cs" />
+    <Compile Include="StreamWriter\StreamWriter.WriteTests.netcoreapp.cs" Condition="'$(TargetGroup)' == 'netcoreapp'" />
     <Compile Include="Stream\Stream.cs" />
     <Compile Include="StreamReader\StreamReader.cs" />
     <Compile Include="StreamReader\StreamReader.StringCtorTests.cs" />

src/System.Runtime.Extensions/src/System/IO/StreamWriter.cs

@@ -2,9 +2,10 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Buffers;
+using System.Diagnostics;
 using System.Text;
 using System.Threading.Tasks;
-using System.Diagnostics;
 
 namespace System.IO
 {
@@ -446,6 +447,21 @@ public override void Write(char[] buffer, int index, int count)
             }
         }
 
+        public override void Write(ReadOnlySpan<char> source)
+        {
+            char[] buffer = ArrayPool<char>.Shared.Rent(source.Length);
+
+            try
+            {
+                source.CopyTo(new Span<char>(buffer));
+                Write(buffer, 0, source.Length);
+            }
+            finally
+            {
+                ArrayPool<char>.Shared.Return(buffer);
+            }
+        }
+
         public override void Write(string value)
         {
             if (value == null)
@@ -555,6 +571,11 @@ public override void WriteLine(string value)
             }
         }
 
+        public override void WriteLine(ReadOnlySpan<char> source)
+        {
+            WriteLine(new string(source.ToArray()));
+        }
+
         #region Task based Async APIs
         public override Task WriteAsync(char value)
         {