ProtobufDecoder

The ProtobufDecoder is a sequencer block, that allows to decode input event data from Protocol Buffers message encoding to output events with decoded data.

Protocol Buffers (protobuf) is a method for serializing structured data, developed by Google. It is designed to be a language-agnostic, platform-neutral, and extensible mechanism for serializing structured data. Protocol Buffers is widely used for communication protocols, data storage, and configuration files, among other things.

Protocol Buffers uses an Interface Definition Language (IDL) to define data structures - message types and their fields. Protocol Buffers definitions are usually contained in the files having .proto extension and have to be compiled to the programming language used by the application using protoc compiler. For this block you only need to copy the definitions into the block Proto attribute value instead and the definitions will be runtime-compiled from there.

Events

Arguments

Properties

Example

The following block diagram shows how to cascade two ProtobufDecoder blocks to decode a Protocol Buffers message SensorTempSamples with the definition like this:

syntax = "proto3";
message TempSample {
  uint64 timestamp = 1;
  double temperature = 2;
}
message SensorTempSamples {
  int32 id = 1;
  repeated TempSample measurements = 2;
}

ProtobufDecoder has argument id added, to instruct the block to decode this field out from incoming message and send it out with Decoded event. Also by adding an output event named measurements to the first ProtobufDecoder, a repeated field named measurements will also be decoded from the input message and all its elements will be emitted with the measurements event to the cascaded ProtobufDecoder1. ProtobufDecoder1 has arguments temp and humidity added, to instruct the block to decode these fields out from incoming message and assign their values as argument values emitted together with Decoded event.

Both ProtobufDecoder's Proto attributes were set to the message definition given above. The ProtobufDecoder Message attribute was set to SensorTempSamples and the ProtobufDecoder1 Message attribute was set to TempSample.

To better understand the data flow, some Sequencer.DebugPrinter blocks were also connected to the blocks to print the time and the data received with events into the application output window. Below is an example output of these debugging blocks for decoding sequence of the SensorTempSamples message for sensor id=101 having 2 TempSamples with temperatures 24.5 and 23.4 (note that the binary values of EncodedMessage argument are logged in hexadecimal form):

15:58:30.123 DEBUG: App.EncodedInputDebug: EventIn: EncodedMessage: 00000000  08 65 12 0f 08 fb 85 c4 a9 06 11 00 00 00 00 00  |.e..............|
15:58:30.123 DEBUG: App.EncodedInputDebug: EventIn: EncodedMessage: 00000010  80 38 40 12 0f 08 a7 88 c4 a9 06 11 66 66 66 66  |.8@.........ffff|
15:58:30.123 DEBUG: App.EncodedInputDebug: EventIn: EncodedMessage: 00000020  66 66 37 40                                      |ff7@|
15:58:30.123 DEBUG: App.RepeatedElementDebug: EventIn: EncodedMessage: 00000000  08 fb 85 c4 a9 06 11 00 00 00 00 00 80 38 40     |.............8@|
15:58:30.123 DEBUG: App.RepeatedElementDebug: EventIn: EncodedMessage: 00000000  08 a7 88 c4 a9 06 11 66 66 66 66 66 66 37 40     |.......ffffff7@|
15:58:30.123 DEBUG: App.DecodedMessageDebug: EventIn: Data arguments: id=101
15:58:30.123 DEBUG: App.DecodeMeasurementDebug: EventIn: Data arguments: timestamp=1697710843;temperature=24.5
15:58:30.123 DEBUG: App.DecodeMeasurementDebug: EventIn: Data arguments: timestamp=1697711143;temperature=23.4