1 files changed, 114 insertions, 12 deletions

diff --git a/src/csharp/Grpc.Core/Marshaller.cs b/src/csharp/Grpc.Core/Marshaller.cs
index 1d758ca935..0af9aa586b 100644
--- a/src/csharp/Grpc.Core/Marshaller.cs
+++ b/src/csharp/Grpc.Core/Marshaller.cs
@@ -29,36 +29,129 @@ namespace Grpc.Core
         readonly Func<T, byte[]> serializer;
         readonly Func<byte[], T> deserializer;
 
+        readonly Action<T, SerializationContext> contextualSerializer;
+        readonly Func<DeserializationContext, T> contextualDeserializer;
+
         /// <summary>
-        /// Initializes a new marshaller.
+        /// Initializes a new marshaller from simple serialize/deserialize functions.
         /// </summary>
         /// <param name="serializer">Function that will be used to serialize messages.</param>
         /// <param name="deserializer">Function that will be used to deserialize messages.</param>
         public Marshaller(Func<T, byte[]> serializer, Func<byte[], T> deserializer)
         {
-            this.serializer = GrpcPreconditions.CheckNotNull(serializer, "serializer");
-            this.deserializer = GrpcPreconditions.CheckNotNull(deserializer, "deserializer");
+            this.serializer = GrpcPreconditions.CheckNotNull(serializer, nameof(serializer));
+            this.deserializer = GrpcPreconditions.CheckNotNull(deserializer, nameof(deserializer));
+            this.contextualSerializer = EmulateContextualSerializer;
+            this.contextualDeserializer = EmulateContextualDeserializer;
         }
 
         /// <summary>
-        /// Gets the serializer function.
+        /// Initializes a new marshaller from serialize/deserialize fuctions that can access serialization and deserialization
+        /// context. Compared to the simple serializer/deserializer functions, using the contextual version provides more
+        /// flexibility and can lead to increased efficiency (and better performance).
+        /// Note: This constructor is part of an experimental API that can change or be removed without any prior notice.
         /// </summary>
-        public Func<T, byte[]> Serializer
+        /// <param name="serializer">Function that will be used to serialize messages.</param>
+        /// <param name="deserializer">Function that will be used to deserialize messages.</param>
+        public Marshaller(Action<T, SerializationContext> serializer, Func<DeserializationContext, T> deserializer)
         {
-            get
-            {
-                return this.serializer;
-            }
+            this.contextualSerializer = GrpcPreconditions.CheckNotNull(serializer, nameof(serializer));
+            this.contextualDeserializer = GrpcPreconditions.CheckNotNull(deserializer, nameof(deserializer));
+            // TODO(jtattermusch): once gRPC C# library switches to using contextual (de)serializer,
+            // emulating the simple (de)serializer will become unnecessary.
+            this.serializer = EmulateSimpleSerializer;
+            this.deserializer = EmulateSimpleDeserializer;
         }
 
         /// <summary>
+        /// Gets the serializer function.
+        /// </summary>
+        public Func<T, byte[]> Serializer => this.serializer;
+
+        /// <summary>
         /// Gets the deserializer function.
         /// </summary>
-        public Func<byte[], T> Deserializer
+        public Func<byte[], T> Deserializer => this.deserializer;
+
+        /// <summary>
+        /// Gets the serializer function.
+        /// Note: experimental API that can change or be removed without any prior notice.
+        /// </summary>
+        public Action<T, SerializationContext> ContextualSerializer => this.contextualSerializer;
+
+        /// <summary>
+        /// Gets the serializer function.
+        /// Note: experimental API that can change or be removed without any prior notice.
+        /// </summary>
+        public Func<DeserializationContext, T> ContextualDeserializer => this.contextualDeserializer;
+
+        // for backward compatibility, emulate the simple serializer using the contextual one
+        private byte[] EmulateSimpleSerializer(T msg)
         {
-            get
+            // TODO(jtattermusch): avoid the allocation by passing a thread-local instance
+            // This code will become unnecessary once gRPC C# library switches to using contextual (de)serializer.
+            var context = new EmulatedSerializationContext();
+            this.contextualSerializer(msg, context);
+            return context.GetPayload();
+        }
+
+        // for backward compatibility, emulate the simple deserializer using the contextual one
+        private T EmulateSimpleDeserializer(byte[] payload)
+        {
+            // TODO(jtattermusch): avoid the allocation by passing a thread-local instance
+            // This code will become unnecessary once gRPC C# library switches to using contextual (de)serializer.
+            var context = new EmulatedDeserializationContext(payload);
+            return this.contextualDeserializer(context);
+        }
+
+        // for backward compatibility, emulate the contextual serializer using the simple one
+        private void EmulateContextualSerializer(T message, SerializationContext context)
+        {
+            var payload = this.serializer(message);
+            context.Complete(payload);
+        }
+
+        // for backward compatibility, emulate the contextual deserializer using the simple one
+        private T EmulateContextualDeserializer(DeserializationContext context)
+        {
+            return this.deserializer(context.PayloadAsNewBuffer());
+        }
+
+        internal class EmulatedSerializationContext : SerializationContext
+        {
+            bool isComplete;
+            byte[] payload;
+
+            public override void Complete(byte[] payload)
+            {
+                GrpcPreconditions.CheckState(!isComplete);
+                this.isComplete = true;
+                this.payload = payload;
+            }
+
+            internal byte[] GetPayload()
+            {
+                return this.payload;
+            }
+        }
+
+        internal class EmulatedDeserializationContext : DeserializationContext
+        {
+            readonly byte[] payload;
+            bool alreadyCalledPayloadAsNewBuffer;
+
+            public EmulatedDeserializationContext(byte[] payload)
+            {
+                this.payload = GrpcPreconditions.CheckNotNull(payload);
+            }
+
+            public override int PayloadLength => payload.Length;
+
+            public override byte[] PayloadAsNewBuffer()
             {
-                return this.deserializer;
+                GrpcPreconditions.CheckState(!alreadyCalledPayloadAsNewBuffer);
+                alreadyCalledPayloadAsNewBuffer = true;
+                return payload;
             }
         }
     }
@@ -77,6 +170,15 @@ namespace Grpc.Core
         }
 
         /// <summary>
+        /// Creates a marshaller from specified contextual serializer and deserializer.
+        /// Note: This method is part of an experimental API that can change or be removed without any prior notice.
+        /// </summary>
+        public static Marshaller<T> Create<T>(Action<T, SerializationContext> serializer, Func<DeserializationContext, T> deserializer)
+        {
+            return new Marshaller<T>(serializer, deserializer);
+        }
+
+        /// <summary>
         /// Returns a marshaller for <c>string</c> type. This is useful for testing.
         /// </summary>
         public static Marshaller<string> StringMarshaller