subscriber.h 文件参考

Read-side primitive of the VLink event communication model. 更多...

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

subscriber.h 的引用(Include)关系图:

此图展示该文件直接或间接的被哪些文件引用了:

浏览源代码.

类
class	vlink::Subscriber< MsgT, SecT >
	Type-safe topic listener for the VLink event communication model. 更多...
class	vlink::SecuritySubscriber< MsgT >
	Convenience alias of Subscriber with per-message decryption enabled. 更多...

命名空间
	vlink

详细描述

Read-side primitive of the VLink event communication model.

Subscriber<MsgT, SecT> attaches a callback to a VLink topic. Each frame delivered by the transport back-end is deserialised into a MsgT instance and forwarded to the user callback registered via listen(). Unlike Getter, the subscriber retains no value history – it simply forwards every event in delivery order.

The class is a thin, header-only template wrapper around SubscriberImpl. Codec dispatch is fully resolved at compile time using the type detected by Serializer::get_type_of<MsgT>().

Event-model Delivery Path

*   Transport Back-end                    Subscriber<MsgT>
*   ------------------                    -----------------
*      | inbound frame                          |
*      |--------------------------------------> |
*      |                                        |  Serializer::deserialize
*      |                                        |  (per-delivery local value)
*      |                                        |
*      |                                        |  optional MessageLoop hop
*      |                                        |
*      |                                        v
*      |                                  user callback(const MsgT&)
* 

Supported Message Types

Category	Example C++ Type	Serializer::Type	Notes
Raw bytes	Bytes	kBytesType	Pass-through to callback.
Protobuf value	MyProto	kProtoType	ParseFromArray path.
Protobuf pointer	MyProto*	kProtoPtrType	Needs bind_proto_arena.
FlatBuffers obj	MyTableT (NativeTable)	kFlatTableType	Object API.
FlatBuffers ptr	MyTable*	kFlatPtrType	Zero-copy view of buffer.
DDS CDR	FastDDS IDL or ROS2 message type	kCdrType	Encapsulated CDR bytes.
POD struct	trivial standard-layout type	kStandardType	sizeof(T) byte copy.
String	std::string	kStringType	Payload-sized byte string.
Custom	type with operator>>/<<	kCustomType	User-supplied codec.

Raw Protobuf pointer receivers allocate a distinct message in the bound Arena for each delivery; that storage remains until the Arena is reset or destroyed.

Basic Listen Example

vlink::Subscriber<MyMsg> sub("dds://vehicle/speed");
sub.listen([](const MyMsg& msg) { handle(msg); });

Callback Dispatch via MessageLoop

vlink::MessageLoop loop;
vlink::Subscriber<MyMsg> sub("dds://vehicle/speed", vlink::InitType::kWithoutInit);
sub.attach(&loop);
sub.init();
sub.listen([](const MyMsg& m) { handle(m); });
loop.run();

Zero-copy Intra Transport

When MsgT is a shared pointer whose element_type derives from IntraDataType (generated via VLINK_INTRA_DATA_DECLARE) and the URL scheme is intra://, the shared pointer is forwarded zero-copy to the callback without serialisation:

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

Latency and Sample-loss Tracking

vlink::Subscriber<MyMsg> sub("dds://my_topic");
sub.set_latency_and_lost_enabled(true);
auto latency_ns = sub.get_latency();
auto stats = sub.get_lost();

警告

For value message types, the deserialised callback argument is a per-delivery local object whose reference is valid only for the callback duration. Pointer-view types may instead refer to an external buffer or arena and follow that storage's lifetime. Copy retained values into explicitly owned storage. Copying Bytes creates owned storage, and copying an IntraData shared pointer extends that object's lifetime.

注解

Calling listen() more than once is a fatal error. The subscriber must be initialised (either by InitType::kWithInit or by explicit init()) before listen() is called.

参见

publisher.h, node.h, serializer.h, base/message_loop.h