subscriber.h File Reference

Type-safe event-model subscriber for VLink topics. More...

#include <functional>
#include <memory>
#include <string>
#include "./impl/subscriber_impl.h"
#include "./node.h"
#include "./internal/subscriber-inl.h"

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Classes
class	vlink::Subscriber< MsgT, SecT >
	Type-safe subscriber for the VLink event communication model. More...
class	vlink::SecuritySubscriber< MsgT >
	Convenience alias for Subscriber with message security enabled. More...

Namespaces
namespace	vlink

Detailed Description

Type-safe event-model subscriber for VLink topics.

Subscriber<MsgT, SecT> is the read side of the VLink event model. It registers a callback that is invoked with each deserialized MsgT message delivered from any matching Publisher on the same URL.

Event Model Data Flow

Publisher<T>              Transport Back-end            Subscriber<T>
    |-- publish(msg) --------> |                             |
    |   serialize(msg)         |-- bytes delivery ---------> |
    |                          |                             |--> callback(msg)
    |                          |                             |    deserialize(bytes)

Supported Message Types

Category	Type	Serializer
Raw bytes	Bytes	kBytesType
Protobuf	MyProto (MessageLite)	kProtoType
Protobuf ptr	MyProto* (Arena-managed)	kProtoPtrType
FlatBuffers	MyTableT (NativeTable)	kFlatTableType
FlatBuffers	MyTable* (Table ptr)	kFlatPtrType
CDR (DDS only)	MyCdrType	kCdrType
Standard layout	POD struct / trivial type	kStandardType
String	std::string	kStringType
Custom	T (has operator>>/<<)	kCustomType

Basic Usage

Subscriber<MyMsg> sub("dds://vehicle/speed");
sub.listen([](const MyMsg& msg) {
    std::cout << "speed: " << msg.value << std::endl;
});

Zero-copy Intra Transport

When MsgT is a shared pointer type whose element_type derives from IntraDataType (generated via VLINK_INTRA_DATA_DECLARE) and the URL uses intra://, the shared pointer is forwarded zero-copy (no serialization):

VLINK_INTRA_DATA_DECLARE(MyProtoMsg, MyIntra)
Subscriber<MyIntra> sub("intra://my_topic");
sub.listen([](const MyIntra& data) { ... });

Latency and Sample-loss Tracking

Subscriber<MyMsg> sub("dds://my_topic");
sub.set_latency_and_lost_enabled(true);
// ... after receiving messages:
int64_t latency_us = sub.get_latency();
SampleLostInfo lost = sub.get_lost();
std::cout << "lost: " << lost.lost << " / " << lost.total << std::endl;

Note

Calling listen() more than once is a fatal error. The subscriber must be initialised before listen() is called.

Template Parameters

MsgT	Message type. Must satisfy Serializer::is_supported().
SecT	Security mode; defaults to SecurityType::kWithoutSecurity.