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#ifndef _PLUGIN_H_
#define _PLUGIN_H_
#include <dlfcn.h>
#include <stdint.h>
#include <pthread.h>
#define PRIVATE(a) a
typedef void* dlhandle_t;
/* Opaque state for a plugin. Not to be touched by the harness (not that it
* really can be.) */
typedef void* opqst_t;
/*
* Structure for the plugin.
*/
typedef struct PLUGIN {
/* Opaque state of this plugin. The state is usually some kind of pointer to
* the plugin state, but all the harness knows is the opaque state is a
* pointer-sized piece of data.
*
* This opaque state is used in a linear pattern where the handlers take the
* opaque state, maybe operate on it, and return a new opaque state, which is
* then passed to the next handler, etc. It is on the plugin to properly
* manager the memory for this state and to destroy it upon teardown.
*
* It's guaranteed that this state is used linearly, meaning the harness gives
* up all ownership to it once passed into a handler. */
PRIVATE(opqst_t state);
/* This plugin's lock. This avoids potential issues with multiple threads
* trying to change the opaque state at once which can lead to undesireable
* outcomes. */
PRIVATE(pthread_mutex_t lock);
/* The handle to the shared library. */
PRIVATE(dlhandle_t library_handle);
/* Pointer to the plugin name. This is in the shared library and a
* null-terminated string. If the library does not have a plugin name, this
* will be NULL. */
PRIVATE(const char* plugin_name);
/** Intializes the plugin with the given argc/argv. This is the first thing
* called on the plugin and is called immediately after the library is loaded.
*/
void (*plugin_load)(int argc, char** argv);
/* Start the plugin with the marshalled state from the previous plugin.
*
* This should return the opaque state from the mashalled_state.
*
* This function should not fail if the state cannot be demarshalled, rather a
* default state should be returned. This is because changing the plugin and
* hot-reloading can produce incompatibilities between the old state and the
* new state, and this should not cause a failure.
*/
opqst_t (*plugin_hot_start)(uint8_t* mashalled_state, uint32_t n);
/*
* Starts the plugin without a marshalled state. Happens during the first boot
* when there is not state.
*/
opqst_t (*plugin_cold_start)();
/*
* Marshals the state to a bytestring. The returned pointer should be malloc'd
* on the heap. The harness takes ownership of the malloc'd pointer.
*
* This is usually called in preparation for a teardown followed by a
* hot-start.
*/
uint8_t* (*plugin_marshal_state)(opqst_t st, uint32_t* szout);
/*
* Teardown the plugin in preperation for the library's imminent unloading.
*/
void (*plugin_teardown)(opqst_t);
/* This anonymous structure contains event handlers. It is wrapped in this
* structure to make it distinct from the management functions above.
*
* The handlers are all optional and if any of them are NULL, the opaque state
* remains untouched.
*/
struct {
/* Right now, empty */
} handlers;
} plugin_t;
/** Loads a plugin from the dynamic library handle. Returns a non-zero error
* code on error. */
int load_plugin_from_dlhandle(plugin_t* out, dlhandle_t library);
/* Like the above, but load the library from the given file. */
int load_plugin_from_file(plugin_t* out, const char* dlfilename);
#endif /* _PLUGIN_H_ */
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