Swap nano from Parser to message factory

This reduces the amount of logic built into the generated code. If we
swap to an alternative form of decoding we should have greater ability
to adapt the existing API to make use of the new one. Previously most
changes would require duplicating all the nano marshalling code.

2 files changed, 8 insertions, 8 deletions

diff --git a/protobuf-nano/src/main/java/io/grpc/protobuf/nano/Parser.java b/protobuf-nano/src/main/java/io/grpc/protobuf/nano/MessageNanoFactory.java
index a82e59f5c..76892c944 100644
--- a/protobuf-nano/src/main/java/io/grpc/protobuf/nano/Parser.java
+++ b/protobuf-nano/src/main/java/io/grpc/protobuf/nano/MessageNanoFactory.java
@@ -31,16 +31,13 @@
 
 package io.grpc.protobuf.nano;
 
-import com.google.protobuf.nano.CodedInputByteBufferNano;
 import com.google.protobuf.nano.MessageNano;
 
-import java.io.IOException;
-
 /**
- * Parser for parsing nano proto messages.
+ * Produce new message instances. Used by a marshaller to deserialize incoming messages.
  *
  * <p>Should be implemented by generated code.
  */
-public interface Parser<T extends MessageNano> {
-  T parse(CodedInputByteBufferNano input) throws IOException;
+public interface MessageNanoFactory<T extends MessageNano> {
+  T newInstance();
 }
diff --git a/protobuf-nano/src/main/java/io/grpc/protobuf/nano/NanoUtils.java b/protobuf-nano/src/main/java/io/grpc/protobuf/nano/NanoUtils.java
index 9375fc8df..43c4b1079 100644
--- a/protobuf-nano/src/main/java/io/grpc/protobuf/nano/NanoUtils.java
+++ b/protobuf-nano/src/main/java/io/grpc/protobuf/nano/NanoUtils.java
@@ -49,7 +49,8 @@ public class NanoUtils {
   private NanoUtils() {}
 
   /** Adapt {@code parser} to a {@code Marshaller}. */
-  public static <T extends MessageNano> Marshaller<T> marshaller(final Parser<T> parser) {
+  public static <T extends MessageNano> Marshaller<T> marshaller(
+      final MessageNanoFactory<T> factory) {
     return new Marshaller<T>() {
       @Override
       public InputStream stream(T value) {
@@ -63,7 +64,9 @@ public class NanoUtils {
           CodedInputByteBufferNano input =
               CodedInputByteBufferNano.newInstance(ByteStreams.toByteArray(stream));
           input.setSizeLimit(Integer.MAX_VALUE);
-          return parser.parse(input);
+          T message = factory.newInstance();
+          message.mergeFrom(input);
+          return message;
         } catch (IOException ipbe) {
           throw Status.INTERNAL.withDescription("Failed parsing nano proto message").withCause(ipbe)
               .asRuntimeException();