[protobuf] Does proto3 allow recursion?

[Zachary Deretsky]

Is recursion handled, for example:

message Node {
string value = 1;
Node parent = 2;
message Child {
 string key = 1;
 Node child = 2;
}
repeated Child children = 3;
}


or

message Node {
string value = 1;
Node parent = 2;
map children = 3;
}




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Re: [protobuf] Dynamic/run-time decoding

[Mike Trienis]

Hi,

Do you know if it's possible do dynamic decoding at run-time using the 
Python API? 

   - https://developers.google.com/protocol-buffers/docs/reference/python/
   
Indeed there is a descriptor.FileDescriptor, however I'm not sure what the 
other classes correspond to?

Thanks, Mike. 

On Tuesday, August 12, 2014 at 10:36:13 AM UTC-7, Feng Xiao wrote:
>
> Protobuf supports creating message types dynamically at runtime and use 
> them for parsing/serialization/etc.
>
> First you need to build up a DescriptorPool 
> 
>  
> that contains all types that you may want to use. There are two approaches 
> to construct this pool. One is to call DescriptorPool::BuildFile() directly 
> with parsed proto files. For example:
>   // Convert .proto files into parsed FileDescriptorProto
>   bool ParseProtoFile(string filename, FileDescriptorProto* result) {
> FileInputStream stream(filename);
> google::protobuf::io::Tokenizer tokenizer(&stream);
> google::protobuf::compiler::Parser parser;
> return parser.Parse(&tokenizer, result);
>   }
>   // Build the descriptor pool
>   DescriptorPool pool;
>   for (string filename : proto_files) {
> FileDescriptorProto proto;
> ParseProtoFile(filename, &proto);
> pool.BuildFile(proto);
>   }
>
> After you have the pool, you can query for a type by its name. For 
> example, DescriptorPool::FindMessageTypeByName().
>
> Then to actually parse/serialize/use message types in the pool, you need 
> to construct message objects around them. DynamicMessage 
> 
>  
> is used for that:
>   // Suppose you want to parse a message type with a specific type name.
>   Descriptor* descriptor = 
> pool.FindMessageTypeByName(message_type_to_parse);
>   DynamicMessageFactory factory;
>   unique_ptr message = factory.GetPrototype(descriptor)->New();
>   // Use the message object for parsing/etc.
>   message->ParseFromString(input_data);
>   // Access a specific field in the message
>   FieldDescriptor* field = descriptor->FindFieldByName(field_to_read);
>   switch (field->type()) {
> case TYPE_INT32: message->GetReflection()->GetInt32(*message, field); 
> break;
> ...
>   }
>
> On Mon, Aug 11, 2014 at 9:31 PM, Jan Kyjovský  > wrote:
>
>> Hi,
>>
>> I have very specific problem. I have data and proto file available and my 
>> application should take both and based on external configuration determine 
>> how to interpret data (many different types/messages in proto). Yet that 
>> can be determine only during run. My question is if there is any support 
>> for that, I mean that I will be able to parse proto and decode data based 
>> on content of interpret intermediate structures.
>>
>> I have been trying to analyze this possibility directly from codes but 
>> not with much success. I would be glad for any guidance.
>>
>> -- 
>> You received this message because you are subscribed to the Google Groups 
>> "Protocol Buffers" group.
>> To unsubscribe from this group and stop receiving emails from it, send an 
>> email to protobuf+u...@googlegroups.com .
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>> .
>> Visit this group at http://groups.google.com/group/protobuf.
>> For more options, visit https://groups.google.com/d/optout.
>>
>
>

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[protobuf] Re: Dynamic/run-time decoding

[Mike Trienis]

Hello,

I would very much like to know if this is possible with the Python API?

   - https://developers.google.com/protocol-buffers/docs/reference/python/ 
   
In other words, if I have a .proto schema file, do I have to use *protoc* 
to compile a python module in order to decode the protobuf message?

Any help would be appreciated, Mike. 


On Monday, August 11, 2014 at 9:31:23 PM UTC-7, Jan Kyjovský wrote:
>
> Hi,
>
> I have very specific problem. I have data and proto file available and my 
> application should take both and based on external configuration determine 
> how to interpret data (many different types/messages in proto). Yet that 
> can be determine only during run. My question is if there is any support 
> for that, I mean that I will be able to parse proto and decode data based 
> on content of interpret intermediate structures.
>
> I have been trying to analyze this possibility directly from codes but not 
> with much success. I would be glad for any guidance.
>

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