THRIFT-5133: Use ArrayPool when reading and writing strings to improve performance
Client: netstd
Patch: Mikel Blanchard

This closes #2057
diff --git a/lib/netstd/Thrift/Protocol/TCompactProtocol.cs b/lib/netstd/Thrift/Protocol/TCompactProtocol.cs
index a8a46f2..bb531f4 100644
--- a/lib/netstd/Thrift/Protocol/TCompactProtocol.cs
+++ b/lib/netstd/Thrift/Protocol/TCompactProtocol.cs
@@ -16,6 +16,7 @@
 // under the License.
 
 using System;
+using System.Buffers;
 using System.Buffers.Binary;
 using System.Collections.Generic;
 using System.Diagnostics;
@@ -66,7 +67,7 @@
 
         // minimize memory allocations by means of an preallocated bytes buffer
         // The value of 128 is arbitrarily chosen, the required minimum size must be sizeof(long)
-        private byte[] PreAllocatedBuffer = new byte[128]; 
+        private readonly byte[] PreAllocatedBuffer = new byte[128]; 
 
         private struct VarInt
         {
@@ -411,11 +412,19 @@
                 return;
             }
 
-            var bytes = Encoding.UTF8.GetBytes(str);
+            var buf = ArrayPool<byte>.Shared.Rent(Encoding.UTF8.GetByteCount(str));
+            try
+            {
+                var numberOfBytes = Encoding.UTF8.GetBytes(str, 0, str.Length, buf, 0);
 
-            Int32ToVarInt((uint) bytes.Length, ref PreAllocatedVarInt);
-            await Trans.WriteAsync(PreAllocatedVarInt.bytes, 0, PreAllocatedVarInt.count, cancellationToken);
-            await Trans.WriteAsync(bytes, 0, bytes.Length, cancellationToken);
+                Int32ToVarInt((uint)numberOfBytes, ref PreAllocatedVarInt);
+                await Trans.WriteAsync(PreAllocatedVarInt.bytes, 0, PreAllocatedVarInt.count, cancellationToken);
+                await Trans.WriteAsync(buf, 0, numberOfBytes, cancellationToken);
+            }
+            finally
+            {
+                ArrayPool<byte>.Shared.Return(buf);
+            }
         }
 
         public override async Task WriteBinaryAsync(byte[] bytes, CancellationToken cancellationToken)
@@ -706,9 +715,17 @@
             }
 
             Transport.CheckReadBytesAvailable(length);
-            var buf = new byte[length];
-            await Trans.ReadAllAsync(buf, 0, length, cancellationToken);
-            return Encoding.UTF8.GetString(buf, 0, length);
+
+            var buf = ArrayPool<byte>.Shared.Rent(length);
+            try
+            {
+                await Trans.ReadAllAsync(buf, 0, length, cancellationToken);
+                return Encoding.UTF8.GetString(buf, 0, length);
+            }
+            finally
+            {
+                ArrayPool<byte>.Shared.Return(buf);
+            }
         }
 
         public override async ValueTask<byte[]> ReadBinaryAsync(CancellationToken cancellationToken)
@@ -717,7 +734,7 @@
             var length = (int) await ReadVarInt32Async(cancellationToken);
             if (length == 0)
             {
-                return new byte[0];
+                return Array.Empty<byte>();
             }
 
             // read data
diff --git a/lib/netstd/Thrift/Thrift.csproj b/lib/netstd/Thrift/Thrift.csproj
index e40db00..b63a12a 100644
--- a/lib/netstd/Thrift/Thrift.csproj
+++ b/lib/netstd/Thrift/Thrift.csproj
@@ -19,7 +19,7 @@
   -->
 
   <PropertyGroup>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFrameworks>netstandard2.1;netstandard2.0</TargetFrameworks>
     <AssemblyName>Thrift</AssemblyName>
     <PackageId>Thrift</PackageId>
     <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
diff --git a/lib/netstd/Thrift/Transport/Client/THttpTransport.cs b/lib/netstd/Thrift/Transport/Client/THttpTransport.cs
index bbd94fa..0790cc8 100644
--- a/lib/netstd/Thrift/Transport/Client/THttpTransport.cs
+++ b/lib/netstd/Thrift/Transport/Client/THttpTransport.cs
@@ -109,7 +109,11 @@
 
             try
             {
+#if NETSTANDARD2_1
+                var ret = await _inputStream.ReadAsync(new Memory<byte>(buffer, offset, length), cancellationToken);
+#else
                 var ret = await _inputStream.ReadAsync(buffer, offset, length, cancellationToken);
+#endif
                 if (ret == -1)
                 {
                     throw new TTransportException(TTransportException.ExceptionType.EndOfFile, "No more data available");
diff --git a/lib/netstd/Thrift/Transport/Client/TNamedPipeTransport.cs b/lib/netstd/Thrift/Transport/Client/TNamedPipeTransport.cs
index f7f10b7..8dab6a0 100644
--- a/lib/netstd/Thrift/Transport/Client/TNamedPipeTransport.cs
+++ b/lib/netstd/Thrift/Transport/Client/TNamedPipeTransport.cs
@@ -72,7 +72,11 @@
             }
 
             CheckReadBytesAvailable(length);
+#if NETSTANDARD2_1
+            var numRead = await PipeStream.ReadAsync(new Memory<byte>(buffer, offset, length), cancellationToken);
+#else
             var numRead = await PipeStream.ReadAsync(buffer, offset, length, cancellationToken);
+#endif
             CountConsumedMessageBytes(numRead);
             return numRead;
         }
diff --git a/lib/netstd/Thrift/Transport/Client/TStreamTransport.cs b/lib/netstd/Thrift/Transport/Client/TStreamTransport.cs
index e04b3b3..ccadad0 100644
--- a/lib/netstd/Thrift/Transport/Client/TStreamTransport.cs
+++ b/lib/netstd/Thrift/Transport/Client/TStreamTransport.cs
@@ -14,7 +14,7 @@
 // KIND, either express or implied. See the License for the
 // specific language governing permissions and limitations
 // under the License.
-
+using System;
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
@@ -82,7 +82,11 @@
                     "Cannot read from null inputstream");
             }
 
+#if NETSTANDARD2_1
+            return await InputStream.ReadAsync(new Memory<byte>(buffer, offset, length), cancellationToken);
+#else
             return await InputStream.ReadAsync(buffer, offset, length, cancellationToken);
+#endif
         }
 
         public override async Task WriteAsync(byte[] buffer, int offset, int length, CancellationToken cancellationToken)
diff --git a/lib/netstd/Thrift/Transport/Server/TNamedPipeServerTransport.cs b/lib/netstd/Thrift/Transport/Server/TNamedPipeServerTransport.cs
index a8b64c4..4b82cbd 100644
--- a/lib/netstd/Thrift/Transport/Server/TNamedPipeServerTransport.cs
+++ b/lib/netstd/Thrift/Transport/Server/TNamedPipeServerTransport.cs
@@ -277,7 +277,11 @@
                 }
 
                 CheckReadBytesAvailable(length);
+#if NETSTANDARD2_1
+                var numBytes = await PipeStream.ReadAsync(new Memory<byte>(buffer, offset, length), cancellationToken);
+#else
                 var numBytes = await PipeStream.ReadAsync(buffer, offset, length, cancellationToken);
+#endif
                 CountConsumedMessageBytes(numBytes);
                 return numBytes;
             }