vcap_writer.h File Reference

Recorder that serialises VLink traffic into the MCAP container (.vcap / .vcapx). More...

#include <memory>
#include <string>
#include "./bag_writer.h"

Include dependency graph for vcap_writer.h:

Go to the source code of this file.

Classes
class	vlink::VCAPWriter
	Concrete MCAP-format BagWriter implementation with optional Zstd compression. More...

Namespaces
	vlink

Detailed Description

Recorder that serialises VLink traffic into the MCAP container (.vcap / .vcapx).

VCAPWriter materialises a BagWriter that emits Foxglove-compatible MCAP files. It inherits the cross-format split-recording machinery from BagWriter and produces files that any MCAP-aware tool can replay. Compression flips between no-compression and Zstd when the build links libzstd; other selectors degrade to plain chunks.

File-format diagram

push_schema()  -->  schema record
push(frame)    -->  channel record (once per URL)
               -->  message chunk (Zstd optional)
on_end()       -->  attachments + summary section + footer (index of summary)

Writer states

+----------+   on_begin()  +---------+   push()/push_schema()   +-----------+
|  closed  | ------------> | opening | -----------------------> | recording |
+----------+               +---------+                          +-----------+
     ^                                                                 |
     |                                                                 v split triggered
     |                                                          +-------------+
     |                                                          | rotating    |
     |                                                          | (new .vcap) |
     |                                                          +-------------+
     |                                                                 |
     +-------------------- on_end() / dtor --------------------- finalising
                                                                       |
                                                                       v
                                                                    sealed

Example

auto writer = vlink::BagWriter::create("/data/recording.vcap");
 
writer->async_run();
writer->push_schema(my_schema);
 
vlink::Frame frame;
frame.timestamp   = -1;  // < 0 => writer auto-assigns from its clock (0 is recorded verbatim)
frame.url         = "dds://lidar/front";
frame.ser_type    = "demo.proto.PointCloud";
frame.schema_type = vlink::SchemaType::kProtobuf;
frame.action_type = vlink::ActionType::kPublish;
frame.data        = serialized_bytes;
writer->push(frame);

See also

BagWriter, VDBWriter