publisher.h File Reference

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

#include <memory>
#include <string>
#include "./impl/publisher_impl.h"
#include "./node.h"
#include "./internal/publisher-inl.h"

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

Namespaces
namespace	vlink

Detailed Description

Type-safe event-model publisher for VLink topics.

Publisher<MsgT, SecT> is the write side of the VLink event model. It serialises a MsgT object and delivers it to all Subscriber nodes that share the same URL.

Event Model Data Flow

Publisher<T>              Transport Back-end            Subscriber<T>
    |                          |                             |
    |-- publish(msg) --------> |                             |
    |   serialize(msg)         |                             |
    |   [loan if shm://]       |-- 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	MyBuilder (has fbb_+Finish)	kFlatBuilderType
CDR (DDS only)	MyCdrType (serialize/des.)	kCdrType
Standard layout	POD struct / trivial type	kStandardType
String	std::string	kStringType
Custom	T (has operator>>/<<)	kCustomType

Subscriber Detection

Publisher<MyMsg> pub("dds://topic");
pub.detect_subscribers([](bool has) {       // async notification
    if (has) pub.publish(MyMsg{});
});
pub.wait_for_subscribers();                 // blocking until subscriber appears
if (pub.has_subscribers()) { ... }          // non-blocking query

Zero-copy on shm://

Publisher<MyStruct> pub("shm://topic");
if (pub.is_support_loan()) {
    Bytes buf = pub.loan(sizeof(MyStruct));
    new (buf.data()) MyStruct{...};
    pub.publish(buf);                       // no copy; loan returned automatically
}

Note

Pass force = true to publish() to send even when no subscribers are present (e.g. for guaranteed-delivery or field-mode semantics).

Template Parameters

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