logger_plugin_interface.h File Reference

Abstract contract for shared-library logger backends loaded via the VLink Plugin system. More...

#include <string_view>
#include "./plugin.h"

Include dependency graph for logger_plugin_interface.h:

Go to the source code of this file.

Classes
class	vlink::LoggerPluginInterface
	Pure-virtual interface that every shared-library logger backend implements. More...

Namespaces
	vlink

Detailed Description

Abstract contract for shared-library logger backends loaded via the VLink Plugin system.

A logger plugin is a shared library that exports a factory through VLINK_PLUGIN_DECLARE and embeds VLINK_PLUGIN_REGISTER inside its concrete subclass. At runtime the host application uses vlink::Plugin::load<LoggerPluginInterface> to construct an instance and forwards every log record to its log method.

Plugin contract

Hook	Direction	Contract
VLINK_PLUGIN_REGISTER	inside the class	Injects get_plugin_id() (ID = demangled name)
VLINK_PLUGIN_DECLARE	translation unit	Exposes the factory and the version metadata
init	host -> plugin	Called once after construction with the app name
log	host -> plugin	Called per record after passing level filters
Destructor	host -> plugin	Called when the host releases the plugin handle

Lifecycle

*  host                          plugin
*  ----                          ------
*  Plugin::load<...> ----------> factory creates instance
*  init(app_name)    ---------->  initialise backend
*  log(level, msg)   ---------->  forward to backend     (repeated)
*  Plugin destroy    ---------->  destroy instance
* 

Loading example

vlink::Plugin plugin;
auto backend = plugin.load<vlink::LoggerPluginInterface>("my_logger_plugin", 1, 0);
 
if (backend) {
  backend->init("my_app");
  backend->log(vlink::Logger::kInfo, "Hello from plugin!");
}

Implementation example

class MyLogger : public vlink::LoggerPluginInterface {
 public:
  bool init(std::string_view app_name) override { return true; }
  bool log(int level, std::string_view str)  override { return write_to_backend(level, str); }
};
VLINK_PLUGIN_DECLARE(MyLogger, 1, 0)

Note

level mirrors vlink::Logger::Level values. Both methods must avoid throwing across the plugin boundary; thrown exceptions there cause undefined behaviour.

See also

Plugin, Logger