Refactoring Java parsing (21.x) (#10665)

* Porting java cleanup

* Update changelog

* Fix absl usage

* Extension patch

* Remove extra allocations

Author: mkruskal-google

CHANGES.txt

@@ -1,3 +1,14 @@
+2022-09-27 version 21.7 (C++/Java/Python/PHP/Objective-C/C#/Ruby)
+  Java
+  * Refactoring java full runtime to reuse sub-message builders and prepare to
+    migrate parsing logic from parse constructor to builder.
+  * Move proto wireformat parsing functionality from the private "parsing
+    constructor" to the Builder class.
+  * Change the Lite runtime to prefer merging from the wireformat into mutable
+    messages rather than building up a new immutable object before merging. This
+    way results in fewer allocations and copy operations.
+  * Make message-type extensions merge from wire-format instead of building up instances and merging afterwards. This has much better performance.
+
 2022-09-13 version 21.6 (C++/Java/Python/PHP/Objective-C/C#/Ruby)
 
 C++

java/core/src/main/java/com/google/protobuf/AbstractMessage.java

@@ -424,27 +424,22 @@ public BuilderType mergeFrom(
         throws IOException {
       boolean discardUnknown = input.shouldDiscardUnknownFields();
       final UnknownFieldSet.Builder unknownFields =
-          discardUnknown ? null : UnknownFieldSet.newBuilder(getUnknownFields());
-      while (true) {
-        final int tag = input.readTag();
-        if (tag == 0) {
-          break;
-        }
-
-        MessageReflection.BuilderAdapter builderAdapter =
-            new MessageReflection.BuilderAdapter(this);
-        if (!MessageReflection.mergeFieldFrom(
-            input, unknownFields, extensionRegistry, getDescriptorForType(), builderAdapter, tag)) {
-          // end group tag
-          break;
-        }
-      }
+          discardUnknown ? null : getUnknownFieldSetBuilder();
+      MessageReflection.mergeMessageFrom(this, unknownFields, input, extensionRegistry);
       if (unknownFields != null) {
-        setUnknownFields(unknownFields.build());
+        setUnknownFieldSetBuilder(unknownFields);
       }
       return (BuilderType) this;
     }
 
+    protected UnknownFieldSet.Builder getUnknownFieldSetBuilder() {
+      return UnknownFieldSet.newBuilder(getUnknownFields());
+    }
+
+    protected void setUnknownFieldSetBuilder(final UnknownFieldSet.Builder builder) {
+      setUnknownFields(builder.build());
+    }
+
     @Override
     public BuilderType mergeUnknownFields(final UnknownFieldSet unknownFields) {
       setUnknownFields(

java/core/src/main/java/com/google/protobuf/ArrayDecoders.java

@@ -237,6 +237,29 @@ static int decodeBytes(byte[] data, int position, Registers registers)
   @SuppressWarnings({"unchecked", "rawtypes"})
   static int decodeMessageField(
       Schema schema, byte[] data, int position, int limit, Registers registers) throws IOException {
+    Object msg = schema.newInstance();
+    int offset = mergeMessageField(msg, schema, data, position, limit, registers);
+    schema.makeImmutable(msg);
+    registers.object1 = msg;
+    return offset;
+  }
+
+  /** Decodes a group value. */
+  @SuppressWarnings({"unchecked", "rawtypes"})
+  static int decodeGroupField(
+      Schema schema, byte[] data, int position, int limit, int endGroup, Registers registers)
+      throws IOException {
+    Object msg = schema.newInstance();
+    int offset = mergeGroupField(msg, schema, data, position, limit, endGroup, registers);
+    schema.makeImmutable(msg);
+    registers.object1 = msg;
+    return offset;
+  }
+
+  @SuppressWarnings({"unchecked", "rawtypes"})
+  static int mergeMessageField(
+      Object msg, Schema schema, byte[] data, int position, int limit, Registers registers)
+      throws IOException {
     int length = data[position++];
     if (length < 0) {
       position = decodeVarint32(length, data, position, registers);
@@ -245,27 +268,28 @@ static int decodeMessageField(
     if (length < 0 || length > limit - position) {
       throw InvalidProtocolBufferException.truncatedMessage();
     }
-    Object result = schema.newInstance();
-    schema.mergeFrom(result, data, position, position + length, registers);
-    schema.makeImmutable(result);
-    registers.object1 = result;
+    schema.mergeFrom(msg, data, position, position + length, registers);
+    registers.object1 = msg;
     return position + length;
   }
 
-  /** Decodes a group value. */
   @SuppressWarnings({"unchecked", "rawtypes"})
-  static int decodeGroupField(
-      Schema schema, byte[] data, int position, int limit, int endGroup, Registers registers)
+  static int mergeGroupField(
+      Object msg,
+      Schema schema,
+      byte[] data,
+      int position,
+      int limit,
+      int endGroup,
+      Registers registers)
       throws IOException {
     // A group field must has a MessageSchema (the only other subclass of Schema is MessageSetSchema
     // and it can't be used in group fields).
     final MessageSchema messageSchema = (MessageSchema) schema;
-    Object result = messageSchema.newInstance();
     // It's OK to directly use parseProto2Message since proto3 doesn't have group.
     final int endPosition =
-        messageSchema.parseProto2Message(result, data, position, limit, endGroup, registers);
-    messageSchema.makeImmutable(result);
-    registers.object1 = result;
+        messageSchema.parseProto2Message(msg, data, position, limit, endGroup, registers);
+    registers.object1 = msg;
     return endPosition;
   }
 
@@ -851,26 +875,19 @@ static int decodeExtension(
           break;
         }
         case ENUM:
-        {
-          IntArrayList list = new IntArrayList();
-          position = decodePackedVarint32List(data, position, list, registers);
-          UnknownFieldSetLite unknownFields = message.unknownFields;
-          if (unknownFields == UnknownFieldSetLite.getDefaultInstance()) {
-            unknownFields = null;
-          }
-          unknownFields =
-              SchemaUtil.filterUnknownEnumList(
-                  fieldNumber,
-                  list,
-                  extension.descriptor.getEnumType(),
-                  unknownFields,
-                  unknownFieldSchema);
-          if (unknownFields != null) {
-            message.unknownFields = unknownFields;
+          {
+            IntArrayList list = new IntArrayList();
+            position = decodePackedVarint32List(data, position, list, registers);
+            SchemaUtil.filterUnknownEnumList(
+                message,
+                fieldNumber,
+                list,
+                extension.descriptor.getEnumType(),
+                null,
+                unknownFieldSchema);
+            extensions.setField(extension.descriptor, list);
+            break;
           }
-          extensions.setField(extension.descriptor, list);
-          break;
-        }
         default:
           throw new IllegalStateException(
               "Type cannot be packed: " + extension.descriptor.getLiteType());
@@ -882,13 +899,8 @@ static int decodeExtension(
         position = decodeVarint32(data, position, registers);
         Object enumValue = extension.descriptor.getEnumType().findValueByNumber(registers.int1);
         if (enumValue == null) {
-          UnknownFieldSetLite unknownFields = ((GeneratedMessageLite) message).unknownFields;
-          if (unknownFields == UnknownFieldSetLite.getDefaultInstance()) {
-            unknownFields = UnknownFieldSetLite.newInstance();
-            ((GeneratedMessageLite) message).unknownFields = unknownFields;
-          }
           SchemaUtil.storeUnknownEnum(
-              fieldNumber, registers.int1, unknownFields, unknownFieldSchema);
+              message, fieldNumber, registers.int1, null, unknownFieldSchema);
           return position;
         }
         // Note, we store the integer value instead of the actual enum object in FieldSet.
@@ -945,38 +957,52 @@ static int decodeExtension(
             value = registers.object1;
             break;
           case GROUP:
-            final int endTag = (fieldNumber << 3) | WireFormat.WIRETYPE_END_GROUP;
-            position = decodeGroupField(
-                Protobuf.getInstance().schemaFor(extension.getMessageDefaultInstance().getClass()),
-                data, position, limit, endTag, registers);
-            value = registers.object1;
-            break;
-
+            {
+              final int endTag = (fieldNumber << 3) | WireFormat.WIRETYPE_END_GROUP;
+              final Schema fieldSchema =
+                  Protobuf.getInstance()
+                      .schemaFor(extension.getMessageDefaultInstance().getClass());
+              if (extension.isRepeated()) {
+                position = decodeGroupField(fieldSchema, data, position, limit, endTag, registers);
+                extensions.addRepeatedField(extension.descriptor, registers.object1);
+              } else {
+                Object oldValue = extensions.getField(extension.descriptor);
+                if (oldValue == null) {
+                  oldValue = fieldSchema.newInstance();
+                  extensions.setField(extension.descriptor, oldValue);
+                }
+                position =
+                    mergeGroupField(
+                        oldValue, fieldSchema, data, position, limit, endTag, registers);
+              }
+              return position;
+            }
           case MESSAGE:
-            position = decodeMessageField(
-                Protobuf.getInstance().schemaFor(extension.getMessageDefaultInstance().getClass()),
-                data, position, limit, registers);
-            value = registers.object1;
-            break;
-
+            {
+              final Schema fieldSchema =
+                  Protobuf.getInstance()
+                      .schemaFor(extension.getMessageDefaultInstance().getClass());
+              if (extension.isRepeated()) {
+                position = decodeMessageField(fieldSchema, data, position, limit, registers);
+                extensions.addRepeatedField(extension.descriptor, registers.object1);
+              } else {
+                Object oldValue = extensions.getField(extension.descriptor);
+                if (oldValue == null) {
+                  oldValue = fieldSchema.newInstance();
+                  extensions.setField(extension.descriptor, oldValue);
+                }
+                position =
+                    mergeMessageField(oldValue, fieldSchema, data, position, limit, registers);
+              }
+              return position;
+            }
           case ENUM:
             throw new IllegalStateException("Shouldn't reach here.");
         }
       }
       if (extension.isRepeated()) {
         extensions.addRepeatedField(extension.descriptor, value);
       } else {
-        switch (extension.getLiteType()) {
-          case MESSAGE:
-          case GROUP:
-            Object oldValue = extensions.getField(extension.descriptor);
-            if (oldValue != null) {
-              value = Internal.mergeMessage(oldValue, value);
-            }
-            break;
-          default:
-            break;
-        }
         extensions.setField(extension.descriptor, value);
       }
     }

java/core/src/main/java/com/google/protobuf/BinaryReader.java

@@ -248,6 +248,15 @@ public <T> T readMessageBySchemaWithCheck(
 
     private <T> T readMessage(Schema<T> schema, ExtensionRegistryLite extensionRegistry)
         throws IOException {
+      T newInstance = schema.newInstance();
+      mergeMessageField(newInstance, schema, extensionRegistry);
+      schema.makeImmutable(newInstance);
+      return newInstance;
+    }
+
+    @Override
+    public <T> void mergeMessageField(
+        T target, Schema<T> schema, ExtensionRegistryLite extensionRegistry) throws IOException {
       int size = readVarint32();
       requireBytes(size);
 
@@ -257,15 +266,10 @@ private <T> T readMessage(Schema<T> schema, ExtensionRegistryLite extensionRegis
       limit = newLimit;
 
       try {
-        // Allocate and read the message.
-        T message = schema.newInstance();
-        schema.mergeFrom(message, this, extensionRegistry);
-        schema.makeImmutable(message);
-
+        schema.mergeFrom(target, this, extensionRegistry);
         if (pos != newLimit) {
           throw InvalidProtocolBufferException.parseFailure();
         }
-        return message;
       } finally {
         // Restore the limit.
         limit = prevLimit;
@@ -290,19 +294,23 @@ public <T> T readGroupBySchemaWithCheck(
 
     private <T> T readGroup(Schema<T> schema, ExtensionRegistryLite extensionRegistry)
         throws IOException {
+      T newInstance = schema.newInstance();
+      mergeGroupField(newInstance, schema, extensionRegistry);
+      schema.makeImmutable(newInstance);
+      return newInstance;
+    }
+
+    @Override
+    public <T> void mergeGroupField(
+        T target, Schema<T> schema, ExtensionRegistryLite extensionRegistry) throws IOException {
       int prevEndGroupTag = endGroupTag;
       endGroupTag = WireFormat.makeTag(WireFormat.getTagFieldNumber(tag), WIRETYPE_END_GROUP);
 
       try {
-        // Allocate and read the message.
-        T message = schema.newInstance();
-        schema.mergeFrom(message, this, extensionRegistry);
-        schema.makeImmutable(message);
-
+        schema.mergeFrom(target, this, extensionRegistry);
         if (tag != endGroupTag) {
           throw InvalidProtocolBufferException.parseFailure();
         }
-        return message;
       } finally {
         // Restore the old end group tag.
         endGroupTag = prevEndGroupTag;