fixes #121: java serialization breaks serializedSize

[eiennohito]

Previously -1 was used as a sentinel value.
However, if a generated case class to be serialized using java serialization,
all backing fields would be reset to 0 because java serialization does not call
constructors.

This fix changes serializedSize default (sentinel) value to 0.
Serialized size of 0 is valid value and it will not be cached if the message
is actually empty.
Still, for such messages computing size should be cheap.

[thesamet]

can you get rid of 'read' and use '__serializedSizeCachedValue` directly instead?

[eiennohito]

It's two field accesses vs one.

JDK's toString hashCode and protobuf's ByteString use similar style:
https://github.com/google/protobuf/blob/master/java/core/src/main/java/com/google/protobuf/ByteString.java#L842

But I can make it back if you still want.

[thesamet]

Got it, no need to change. Will merge in.

On Wed, Jun 1, 2016 at 6:32 AM, Arseny Tolmachev notifications@github.com
wrote:

In
compiler-plugin/src/main/scala/com/trueaccord/scalapb/compiler/ProtobufGenerator.scala
#122 (comment):

@@ -382,8 +382,14 @@ class ProtobufGenerator(val params: GeneratorParams) extends DescriptorPimps {
.add("}")
.add("final override def serializedSize: Int = {")
.indent

•  .add("if (__serializedSizeCachedValue == -1) { __serializedSizeCachedValue = __computeSerializedValue() }")
  

•  .add("__serializedSizeCachedValue")
  

•  .add("var read = __serializedSizeCachedValue")
  

It's two field accesses vs one.

JDK's toString hashCode and protobuf's ByteString use similar style:

https://github.com/google/protobuf/blob/master/java/core/src/main/java/com/google/protobuf/ByteString.java#L842

But I can make it back if you still want.

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-Nadav