Re: [infinispan-dev] Avoid Collections.emptySet() / emptyMap() / emptyList
On Oct 22, 2012, at 3:40 PM, David M. Lloyd <david.lloyd(a)redhat.com> wrote:
On 10/22/2012 01:41 AM, Galder Zamarreño wrote:
>
> On Oct 19, 2012, at 7:20 PM, David M. Lloyd <david.lloyd(a)redhat.com> wrote:
>
>> Also be aware that JBMAR has specific optimizations for the JDK empty
>> collections - they are represented by a single byte in the stream.
>
> Well, it's actually 3 bytes that you use to represent empty collections (at least
in 1.3.15ga):
>
> write(ID_NEW_OBJECT);
> write(ID_CLASS_CLASS);
> write(classByte);
>
> Whereas with our externalizers, these get resolved via object writer (which gets
called before your code to detect empty collections) and it only writes 1 byte:
>
> write(externalizerId);
No, that's inaccurate; they are singletons and do not use ID_NEW_OBJECT.
Really?
https://github.com/dmlloyd/jboss-marshalling/blob/1.3.15.GA/river/src/mai...
They're done as instances so it is one of:
public static final int ID_EMPTY_LIST_OBJECT = 0x5d;
public static final int ID_EMPTY_SET_OBJECT = 0x62;
public static final int ID_EMPTY_MAP_OBJECT = 0x69;
Your externalizers on the other hand take multiple bytes even in the
simplest case. If it is that important, you could use an ObjectResolver
to swap in the JDK instance instead of using yet another externalizer
(which has several bytes of overhead of its own).
Well, to be completely precise, our version will write two bytes:
1st byte:
https://github.com/dmlloyd/jboss-marshalling/blob/1.3.15.GA/river/src/mai...
2nd byte:
https://github.com/galderz/infinispan/blob/t_memory/core/src/main/java/or...
I still see 3 bytes written in your case:
1st byte:
https://github.com/dmlloyd/jboss-marshalling/blob/1.3.15.GA/river/src/mai...
2nd byte:
https://github.com/dmlloyd/jboss-marshalling/blob/1.3.15.GA/river/src/mai...
3rd byte: class byte, as indicated in
https://github.com/dmlloyd/jboss-marshalling/blob/1.3.15.GA/river/src/mai...
Not sure if you remember but we have ObjectTable.Writer in what we call ExternalizerTable,
which given a type, it resolves into an Infinispan Externalizer.
Now, given Collections.Empty<Set>, it will resolve to an adapter that writes the ID
of the externalizer (in this case InfinsipanCollections.EmptySet.Externalizer), and then
will delegate to its writeObject, which does nothing.
--
- DML
_______________________________________________
infinispan-dev mailing list
infinispan-dev(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/infinispan-dev
--
Galder Zamarreño
galder(a)redhat.com
twitter.com/galderz
Project Lead, Escalante
http://escalante.io
Engineer, Infinispan
http://infinispan.org