dynamic_data.h File Reference

Self-describing serialised payload tagged with an inline type name. More...

#include <memory>
#include <string_view>
#include <utility>
#include "../serializer.h"

Include dependency graph for dynamic_data.h:

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Classes
class	vlink::DynamicData
	Type-erased wrapper that pairs an inline type name with a serialised payload. More...

Namespaces
	vlink

Detailed Description

Self-describing serialised payload tagged with an inline type name.

DynamicData carries a serialised VLink-compatible message together with a short type-name tag inside a single Bytes buffer. The first kOffset = 20 bytes of the buffer hold the type name (NUL-padded), and the remainder holds the payload as produced by Serializer. This layout lets transports route, log and inspect a payload without knowing its concrete C++ type at compile time – the recipient picks the matching deserialiser at run time using the embedded tag.

Supported dynamic categories (chosen automatically by Serializer):

Category	Examples	Notes
Protobuf	MyProto, std::shared_ptr<P>	Encoded with the message's wire format
FlatBuffer	MyTable, FlatPtr<T>	Encoded via FlatBuilder
POD/Std	int, struct Foo (trivial)	Standard layout copy
Bytes	vlink::Bytes	Stored verbatim
String	std::string	Length-prefixed
Chars	char[N], const char*	NUL-terminated
Custom	Types with explicit Serializer	User-provided serialise/deserialise hooks

Two categories are forbidden and rejected by static_assert: nested DynamicData (avoids recursive type-name layout) and CDR types (their wire format does not allow the in-place prefix used here). The type-name literal (including its trailing NUL) must fit in fewer than kOffset bytes.

Buffer layout:

*   +----------------------------+-----------------------------------------+
*   |  type name (20 bytes max)  |  serialised payload                     |
*   +----------------------------+-----------------------------------------+
*   ^                            ^
*   data_.real_data()            data_.real_data() + kOffset
* 

Example

vlink::DynamicData dd;
MyProtoMsg msg;
msg.set_value(42);
dd.load("MyProtoMsg", msg);                     // serialise + tag
 
// Send over any transport that handles vlink::Bytes:
vlink::Bytes wire;
dd >> wire;
 
vlink::DynamicData received;
received << wire;                               // recover the tagged blob
if (received.get_type() == "MyProtoMsg") {
  MyProtoMsg out = received.as<MyProtoMsg>();   // deserialise
  (void)out;
}