[Rprotobuf-yada] grab the descriptor from the Descriptor pool

[Romain François]

Hi,

Now grabbing the Descriptor [1] pointer for a given message type and 
bring it into the R side as an external pointer.

# person.proto is in the current working directory
 > RProtoBuf:::readProtoFiles()
<readProtoFiles>
[1] "/tmp/person.proto"
    importer.Import( '/tmp/person.proto' )
   name    = /tmp/person.proto
   package = tutorial
   number of top level message types = 2
        0  : tutorial.Person
        1  : tutorial.AddressBook
   number of top level enum types = 0
   Retrieve the 'tutorial.Person' descriptor from the pool
   4 fields
        [0] : name (tag number=1, type=9)
        [1] : id (tag number=2, type=5)
        [2] : email (tag number=3, type=9)
        [3] : phone (tag number=4, type=11)
</readProtoFiles>

# all the messages above will disappear, it is just debug info/learning 
stuff

# now that the descriptor pool knows about the Person message type,
# we can grab the descriptor

 > RProtoBuf:::getProtobufDescriptor( "tutorial.Person" )
<getProtobufDescriptor>
       type = [1] "tutorial.Person"
</getProtobufDescriptor>
<pointer: 0x8771140>

# we don't know this message type, so we get NULL

 > RProtoBuf:::getProtobufDescriptor( "bla.bla.Yada" )
<getProtobufDescriptor>
       type = [1] "bla.bla.Yada"
NULL

Romain


[1] 
http://code.google.com/apis/protocolbuffers/docs/reference/cpp/google.protobuf.descriptor.html#Descriptor

-- 
Romain Francois
Professional R Enthusiast
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr
|- http://tr.im/BcPw : celebrating R commit #50000
|- http://tr.im/ztCu : RGG #158:161: examples of package IDPmisc
`- http://tr.im/yw8E : New R package : sos