protobuf: Support encoding Enums

Encode enum values using their ordinal as a varint, similar to
what the proto compiler from Google would do.  This requires that
application developers carefully assign their enum orders in order
to maintain values already encoded in protobufs.

Change-Id: I1f40170c583125f425f4ff4a3aa7045ee0a820ca
Signed-off-by: Shawn O. Pearce <sop@google.com>

3 files changed, 52 insertions, 1 deletions

diff --git a/src/main/java/com/google/gwtorm/protobuf/CodecGen.java b/src/main/java/com/google/gwtorm/protobuf/CodecGen.java
index a7ab7ef..5a5342b 100644
--- a/src/main/java/com/google/gwtorm/protobuf/CodecGen.java
+++ b/src/main/java/com/google/gwtorm/protobuf/CodecGen.java
@@ -51,6 +51,7 @@ class CodecGen<T> implements Opcodes {
       Type.getType(java.util.Collection.class);
   private static final Type iterator = Type.getType(java.util.Iterator.class);
   private static final Type string = Type.getType(String.class);
+  private static final Type enumType = Type.getType(Enum.class);
   private static final Type byteString = Type.getType(ByteString.class);
   private static final Type object = Type.getType(Object.class);
   private static final Type codedOutputStream =
@@ -495,6 +496,15 @@ class CodecGen<T> implements Opcodes {
               .getMethodDescriptor(Type.LONG_TYPE, new Type[] {}));
           cgs.doinc("computeFixed64Size", Type.INT_TYPE, Type.LONG_TYPE);
 
+        } else if (f.getPrimitiveType().isEnum()) {
+          cgs.preinc();
+          cgs.push(f.getColumnID());
+          cgs.pushFieldValue();
+          mv.visitMethodInsn(INVOKEVIRTUAL, enumType.getInternalName(),
+              "ordinal", //
+              Type.getMethodDescriptor(Type.INT_TYPE, new Type[] {}));
+          cgs.doinc("computeEnumSize", Type.INT_TYPE, Type.INT_TYPE);
+
         } else {
           throw new OrmException("Type " + f.getPrimitiveType()
               + " not supported for field " + f.getPathToFieldName());
@@ -764,6 +774,12 @@ class CodecGen<T> implements Opcodes {
                 .getMethodDescriptor(Type.LONG_TYPE, new Type[] {}));
             cgs.write("writeFixed64", Type.LONG_TYPE);
 
+          } else if (f.getPrimitiveType().isEnum()) {
+            mv.visitMethodInsn(INVOKEVIRTUAL, enumType.getInternalName(),
+                "ordinal", //
+                Type.getMethodDescriptor(Type.INT_TYPE, new Type[] {}));
+            cgs.write("writeEnum", Type.INT_TYPE);
+
           } else {
             throw new OrmException("Type " + f.getPrimitiveType()
                 + " not supported for field " + f.getPathToFieldName());
@@ -1128,6 +1144,14 @@ class CodecGen<T> implements Opcodes {
               Type.getMethodDescriptor(Type.VOID_TYPE,
                   new Type[] {Type.LONG_TYPE}));
 
+        } else if (f.getPrimitiveType().isEnum()) {
+          Type et = Type.getType(f.getPrimitiveType());
+          mv.visitMethodInsn(INVOKESTATIC, et.getInternalName(), "values", Type
+              .getMethodDescriptor(Type.getType("[" + et.getDescriptor()),
+                  new Type[] {}));
+          cgs.call("readEnum", Type.INT_TYPE);
+          mv.visitInsn(AALOAD);
+
         } else {
           throw new OrmException("Type " + f.getPrimitiveType()
               + " not supported for field " + f.getPathToFieldName());
diff --git a/src/main/java/com/google/gwtorm/schema/Util.java b/src/main/java/com/google/gwtorm/schema/Util.java
index ff34f0a..1ca5e5d 100644
--- a/src/main/java/com/google/gwtorm/schema/Util.java
+++ b/src/main/java/com/google/gwtorm/schema/Util.java
@@ -67,7 +67,7 @@ public class Util {
     if (type == null || type == Void.TYPE) {
       return false;
     }
-    if (type.isPrimitive()) {
+    if (type.isPrimitive() || type.isEnum()) {
       return true;
     }
     if (type == String.class) {
diff --git a/src/test/java/com/google/gwtorm/protobuf/ProtobufEncoderTest.java b/src/test/java/com/google/gwtorm/protobuf/ProtobufEncoderTest.java
index 14544c0..21007f6 100644
--- a/src/test/java/com/google/gwtorm/protobuf/ProtobufEncoderTest.java
+++ b/src/test/java/com/google/gwtorm/protobuf/ProtobufEncoderTest.java
@@ -197,6 +197,24 @@ public class ProtobufEncoderTest extends TestCase {
     assertEquals(2, other.list.size());
   }
 
+  public void testEnumEncoder() throws UnsupportedEncodingException {
+    assertEquals(1, ThingWithEnum.Type.B.ordinal());
+    assertSame(ThingWithEnum.Type.B, ThingWithEnum.Type.values()[1]);
+
+    ProtobufCodec<ThingWithEnum> e = CodecFactory.encoder(ThingWithEnum.class);
+
+    ThingWithEnum thing = new ThingWithEnum();
+    thing.type = ThingWithEnum.Type.B;
+
+    ThingWithEnum other = e.decode(e.encodeToByteArray(thing));
+    assertNotNull(other.type);
+    assertSame(thing.type, other.type);
+
+    byte[] act = e.encodeToByteArray(thing);
+    byte[] exp = {0x08, 0x01};
+    assertEquals(asString(exp), asString(act));
+  }
+
   private static String asString(byte[] bin)
       throws UnsupportedEncodingException {
     return new String(bin, "ISO-8859-1");
@@ -247,4 +265,13 @@ public class ProtobufEncoderTest extends TestCase {
     @CustomCodec(ItemCodec.class)
     List<Item> list;
   }
+
+  static class ThingWithEnum {
+    static enum Type {
+      A, B;
+    }
+
+    @Column(id = 1)
+    Type type;
+  }
 }