On Wed, Jun 24, 2009 at 6:15 AM, Toph <clo...@gmail.com> wrote:

>
> Thanks for the reply Kenton.
>
> Yes I discovered UnknownFieldSet, although it (and thus its toString
> () ) isn't able to recurse down a tree of embedded messages stored in
> length-delimited values (as far as I can see), so I've written a
> recursive method to do just that (which has to try to parse such a
> value in order to determine if it is an embedded message, or just a
> bunch of bytes/text).


Right, there is no way to distinguish between embedded messages and byte
blobs without having the proto definition.

I believe the C++ TextFormat code heuristically detects embedded messages
when printing unknown fields, the same way you do.  I don't think that's
been ported to Java, though.


> Is UnknownFieldSet able to handle packed repeated fields correctly and
> parse them out of the length delimited value into one of the
> UnknownFieldSet.Field.get*List() Lists, as opposed to just leaving
> them packed in the value (as it does with embedded messages) ?  I
> assume so, but haven't tried it.


No.  Again, this requires knowing the proto definition.  There's no way to
distinguish between packed arrays and byte blobs given only the encoded
message.


> I'm ok with the interface changing in a future version as long as it
> supports extracting all of the data that it does today.


Yes, it will contain all the same data, but it will no longer group the data
by field number.  Instead it will just have an array of number/value pairs
in arbitrary order (with groups still represented as embedded
UnknownFieldSets).


>
>
> On Jun 24, 2:12 am, Kenton Varda <ken...@google.com> wrote:
> > You can use UnknownFieldSet, but be warned that the interface for that
> class
> > is likely to change in a future version (because the current design is
> > somewhat inefficient).  If you just want to print the contents, you
> should
> > be fine -- just parse into an UnknownFieldSet and then call its
> toString()
> > method.  Those parts won't change.
> >
> >
> >
> > On Tue, Jun 23, 2009 at 7:46 AM, Toph <clo...@gmail.com> wrote:
> >
> > > Hi folks,
> >
> > > I understand that protocol buffers messages are not fully self-
> > > describing.
> > > However, the message contains the field number, wire type, and value,
> > > right?
> >
> > > In Java, how can I take a byte[] (array of bytes) that represents a
> > > message and deserialize it into a list of tuples that contain the
> > > field number, wire type, and value?  I really just want to print out
> > > these tuples, even if the value is binary.
> >
> > > Do any of the classes i the Java API provide a mechanism to do this?
> > > I know I could just take the documentation of the encoding and write
> > > code myself, but I am hoping that one of the API classes exists in a
> > > usable or near-usable form to do this for me.  Will CodedInputStream
> > > do it?  Can I use any of the parseFrom() or mergeFrom() methods?
> >
> > > Note that I do not have the corresponding .proto file in source form,
> > > compiled form, or available to transmit along with any messages
> >
> > > Thanks
> >
>

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