#ifndef MODULE_H
#define MODULE_H
/**
* @file
*
* Dynamically loadable modules for use with nexus.
*
* The modules are loaded using dlopen(), and hence should be standard dynamic libraries. Module initialization happens
* using a module_init_func_t named "<name>_init", which should return some kind of context pointer, which can later be
* used to perform other operations on the module.
*/
#include "nexus.h"
#include "error.h"
#include <sys/queue.h>
/**
* Information required to load/identify a module.
*/
struct module_info {
/** Human-readable name */
const char *name;
/** Filesystem path to the .so */
const char *path;
};
/**
* A module's behaviour is defined as a set of function pointers, which is dynamically resolved from the module DSO,
* using the <mod_name>_funcs symbol.
*/
struct module_funcs {
/**
* Initialize the module, returning an opaque context pointer that is stored in the module state, and supplied for
* subsequent calls. The supplied nexus arg can be used to access the global state.
*
* @param nexus a pointer to the nexus struct containing the global state
* @param ctx_ptr the context pointer should be returned via this
* @param err returned error info
*/
err_t (*init) (struct nexus *nexus, void **ctx_ptr, struct error_info *err);
/**
* Set a configuration option with the given name and value, given by the user. Configuration settings are not
* regarded as unique-per-name, but rather, several invocations of 'conf' with the same name and different values
* could set up a multitude of things.
*
* XXX: make value a non-modifyable string
*
* @param ctx the module's context pointer as returned by init
* @param name the name of the configuration setting
* @param value the value of the configuration setting
* @param err returned error info
*/
err_t (*conf) (void *ctx, const char *name, char *value, struct error_info *err);
};
/**
* A loaded module.
*/
struct module {
/** The identifying info for the module */
struct module_info info;
/** The dlopen handle */
void *handle;
/** The resolved function table */
struct module_funcs *funcs;
/** The module context object */
void *ctx;
/** Our entry in the list of modules */
TAILQ_ENTRY(module) modules_list;
};
/**
* A set of loaded modules, and functionality to load more
*/
struct modules {
/** The nexus in use */
struct nexus *nexus;
/** List of loaded modules */
TAILQ_HEAD(module_ctx_modules, module) list;
};
/**
* Possible error codes
*/
enum module_error_code {
_ERR_MODULE_BEGIN = _ERR_MODULE,
ERR_MODULE_OPEN, ///< dlopen() failed
ERR_MODULE_NAME, ///< invalid module_info.name
ERR_MODULE_SYM, ///< invalid symbol
ERR_MODULE_INIT_FUNC, ///< invalid module_init_func_t
ERR_MODULE_CONF, ///< value error in configuration data
};
/**
* Maximum length of a module name
*/
#define MODULE_NAME_MAX 24
/**
* Maximum length of module symbol suffix
*/
#define MODULE_SUFFIX_MAX 16
/**
* Maximum length of symbol name name, including terminating NUL
*/
#define MODULE_SYMBOL_MAX (MODULE_NAME_MAX + 1 + MODULE_SUFFIX_MAX + 1)
/**
* Create a new modules state
*/
err_t modules_create (struct modules **modules_ptr, struct nexus *nexus);
/**
* Load a new module
*/
err_t module_load (struct modules *modules, struct module **module_ptr, const struct module_info *info, struct error_info *err);
/**
* Set a module configuration option
*/
err_t module_conf (struct module *module, const char *name, char *value, struct error_info *err);
/**
* Unload a module
*
* XXX: not implemented
*/
err_t module_unload (struct module *module);
#endif