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Module Loading

Module Loading — Handling of dynamic shared objects (DSOs)

Synopsis


#include <monitor/monitor.h>


            mon_module;
enum        mon_api_category;
#define     MON_MODSYM                      (a)
            mon_symbol_info;
int         mon_module_load                 (const char *filename,
                                             const mon_symbol_info symbols[],
                                             mon_cfg_node *config,
                                             GList **modules);
int         mon_module_scan                 (mon_cfg_node *cfgroot,
                                             const mon_symbol_info symbols[],
                                             int def_autoload,
                                             GList **modules);
int         mon_module_init                 (mon_module *module);
void        mon_module_ref                  (mon_module *module);
void        mon_module_done                 (mon_module *module);
mon_cfg_node* mon_module_config             (mon_module *module);
char**      mon_module_list                 (void);
#define     mon_modlog                      (level, fmt, ...)

            mon_static_file;
            mon_static_symtab;
void        mon_module_register_static      (const mon_static_file *filetab);

Description

Details

mon_module

typedef struct {
	/* These should be the first field */
	mon_api_category	api_category : 16;
	int			api_version : 16;

	const char		*name;
	int			ver_major;
	int			ver_minor;
	unsigned int		flags;
	int			(*module_init)(mon_module *module,
					mon_cfg_node *cfg);
	void			(*module_done)(mon_module *module);

	const mon_cfg_desc	*parameters;

	int			refcnt;
} mon_module;

Information about aloadable module.

mon_api_category api_category : 16;the mon_api_category the module uses.
int api_version : 16;the API version the module implements.
const char *name;the name of the module.
int ver_major;the module's major version number.
int ver_minor;the module's minor version number.
unsigned int flags;module flags.
module_init ()the module's initialization function.
module_done ()the module's finalization function.
const mon_cfg_desc *parameters;list of module parameter descriptors.
int refcnt;reference count.

enum mon_api_category

typedef enum {
	MON_API_REGISTRY,
	MON_API_AUTH_CLIENT,
	MON_API_AUTH_SERVER,
	MON_API_PROTO_CONSUMER,
	MON_API_PROTO_PRODUCER,
	MON_API_SENSOR,
	MON_API_ACTUATOR,
	MON_API_REGISTRY_PRODUCER
} mon_api_category;

API categories used in the monitoring system.

MON_API_REGISTRYthe registry API.
MON_API_AUTH_CLIENTthe client-side authentication API.
MON_API_AUTH_SERVERthe server-side authentication API.
MON_API_PROTO_CONSUMERthe consumer-side protocol API.
MON_API_PROTO_PRODUCERthe producer-side protocol API.
MON_API_SENSORthe sensor API.
MON_API_ACTUATORthe actuator API.
MON_API_REGISTRY_PRODUCERthe async registry API.

MON_MODSYM()

#define     MON_MODSYM(a)

This macro helps static linking. If a module is linked statically, the name of the module is appended to the symbol to make it unique.

a :a symbol name that is exported by a module.

mon_symbol_info

typedef struct {
	const char		*description;
	const char		*symbol;
	int			init_order;
	int			(*mod_register)(mon_module *module);
	void			(*mod_unregister)(mon_module *module);
} mon_symbol_info;

Describes a symbol that is exported by a module.

const char *description;description of this symbol.
const char *symbol;the name of the symbol.
int init_order;number defining the initialization order.
mod_register ()function to call when this symbol is found in a module.
mod_unregister ()function to call when the module is about to be unloaded.

mon_module_load ()

int         mon_module_load                 (const char *filename,
                                             const mon_symbol_info symbols[],
                                             mon_cfg_node *config,
                                             GList **modules);

Loads a module.

filename :name of the DSO to load.
symbols :description of the symbols to look for.
config :configuration information for this DSO.
modules :list to append all modules that has been found.
Returns :0 if successful or an error code.

mon_module_scan ()

int         mon_module_scan                 (mon_cfg_node *cfgroot,
                                             const mon_symbol_info symbols[],
                                             int def_autoload,
                                             GList **modules);

Scans a directory for modules to load.

This function examines every shared object in the mod_path directory and looks for the symbols named sym_names. If all the requested symbols were found in the module, their values along are passed to the cb function along with the file name and the supplied cb_arg pointer. If the callback function returns 0, the module is registered as loaded; otherwise, the module is unloaded.

cfgroot :root of the configuration tree that contains the configuration of modules.
symbols :desrcription of the symbols to look for.
def_autoload :default value for autoload.
modules :pointer to store the list of loaded mon_module descriptors if successful.
Returns :0 if successful or an error code.

mon_module_init ()

int         mon_module_init                 (mon_module *module);

Initializes a loaded module.

module :a mon_module.
Returns :0 if successful or an error code.

mon_module_ref ()

void        mon_module_ref                  (mon_module *module);

Increments the reference count of a mon_module.

module :a mon_module

mon_module_done ()

void        mon_module_done                 (mon_module *module);

Decrements the reference count of a mon_module. If the reference count reaches zero, the module is unloaded.

module :a mon_module.

mon_module_config ()

mon_cfg_node* mon_module_config             (mon_module *module);

Returns the configuration node for the module that was specified in the symbols argument of mon_module_scan().

module :a mon_module.
Returns :a mon_cfg_node or NULL if the module was not loaded by mon_module_scan().

mon_module_list ()

char**      mon_module_list                 (void);

Returns the list of currently loaded modules.

Returns :a NULL-terminated list of modules.

mon_modlog()

#define     mon_modlog(level, fmt, ...)

Convinience function for modules. It calls mon_log() with the given arguments but precedes every message with the module name.

level :the severity of the message.
fmt :the format string.
... :variadic parameters matching the format string.

mon_static_file

typedef struct {
	const char		*const name;
	const mon_static_symtab	*const symtab;
} mon_static_file;

Describes a statically linked module.

const char *const  name;the virtual filename of the module.
const mon_static_symtab *const  symtab;the list of symbols this module exports.

mon_static_symtab

typedef struct {
	const char		*const name;
	const void		*value;
} mon_static_symtab;

Describes a symbol for a statically linked module.

const char *const  name;the name of the symbol.
const void *value;the value of the symbol.

mon_module_register_static ()

void        mon_module_register_static      (const mon_static_file *filetab);

Registers a statically linked module.

filetab :list of mon_static_file entries to register. The list must be terminated by an entry that has its name field set to NULL.
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