plugin

Simple portable plugin library.

Plugins accessed with this library, are dynamic shared libraries exposing a single function with prototype

const PluginAPI *symbol(void *state, int *iter);

This function should return a pointer to a struct with function pointers to all functions provided by the plugin (data member are also allowed). Below we refer to this struct as the plugin API. The first element in the API must be a pointer to a string containg the name of the plugin. Plugin names should be unique.

The state argument is used to pass a pointer to the global state of the caller to the plugin. You may use the session.h module for that.

The iter argument is normally ignored. It is provided to support plugins exposing several APIs. *iter will be zero at the first time the function is called. If the plugin has more APIs to expose, it should increase *iter by one to indicate that it should be called again to return the next API. When returning the last API, it should leave *iter unchanged.

A new plugin kind, with its own API, can be created with plugin_info_create().

See also

http://gernotklingler.com/blog/creating-using-shared-libraries-different-compilers-different-operating-systems/

Defines

PluginAPI_HEAD

Initial fields in all plugin APIs.

Typedefs

typedef struct _PluginAPI PluginAPI

Base declaration of a plugin API that all plugin APIs can be cast into.

typedef const PluginAPI *(*PluginFunc)(void *state, int *iter)

Prototype for function that is looked up in shared library. See above for more info.

typedef struct _Plugin Plugin

Opaque struct for list of loaded plugins (shared libraries)

typedef struct _PluginInfo PluginInfo

Info about a plugin kind

typedef struct _PluginIter PluginIter

Struct for iterating over registered plugins

Enums

enum PluginErrCodes

Values:

enumerator pluginMemoryError

Out of memory

Functions

PluginInfo *plugin_info_create(const char *kind, const char *symbol, const char *envvar, void *state)

Creates a new plugin kind and returns a pointer to information about it.

kind is the name of the new plugin kind. symbol is the name of the function that plugins should define. envvar is the name of environment variable with plugin search path. state pointer to global state passed to the plugin function.

Returns NULL on error.

void plugin_info_free(PluginInfo *info)

Free’s plugin info.

int plugin_register_api(PluginInfo *info, const PluginAPI *api)

Register a plugin api not associated to a dynamic loadable library.

This function may e.g. be useful for registering plugins written in dynamic interpreted languages, like Python.

int plugin_has_api(PluginInfo *info, const char *name)

Returns non-zero if plugin api name is already registered.

const PluginAPI *plugin_get_api(PluginInfo *info, const char *name, int errcode)

Returns pointer to plugin api.

If a plugin with the given name is already registered, it is returned.

Otherwise the plugin search path is checked for shared libraries matching name.EXT where EXT is the extension for shared library on the current platform (“dll” on Windows and “so” on Unix/Linux). If a plugin with the provided name is fount, it is loaded, registered and returned.

Otherwise the plugin search path is checked again, but this time for any shared library. If a plugin with the provided name is found, it is loaded, registered and returned.

If the plugin is not found, err() is called with eval set to errcode.

Otherwise NULL is returned.

void plugin_load_all(PluginInfo *info)

Load all plugins that can be found in the plugin search path. Returns non-zero on error.

void plugin_api_iter_init(PluginIter *iter, const PluginInfo *info)

Initiates a plugin iterator.

const PluginAPI *plugin_api_iter_next(PluginIter *iter)

Returns pointer to the next registered API or NULL if all APIs have been visited.

Used for iterating over plugins. Plugins should not be registered or removed while iterating.

int plugin_unload(PluginInfo *info, const char *name)

Unloads and unregisters plugin with the given name. Returns non-zero on error.

char **plugin_names(const PluginInfo *info)

Returns a NULL-terminated array of pointers to api names. Returns NULL on error.

const char **plugin_path_get(PluginInfo *info)

Returns a NULL-terminated array of pointers to search paths or NULL if no search path is defined.

int plugin_path_insert(PluginInfo *info, const char *path, int n)

Inserts path into the current search path at index n. If n is negative, it counts from the end of the search path (like Python).

If n is out of range, it is clipped.

Returns the index of the newly inserted path or -1 on error.

int plugin_path_append(PluginInfo *info, const char *path)

Appends path into the current search path.

Returns the index of the newly appended path or -1 on error.

int plugin_path_appendn(PluginInfo *info, const char *path, size_t n)

Like plugin_path_append(), but appends at most the n first bytes of path to the current search path.

Returns the index of the newly appended path or -1 on error.

int plugin_path_extend(PluginInfo *info, const char *s, const char *pathsep)

Extends current search path by appending all pathsep-separated paths in s to it.

Returns the index of the last appended path or zero if nothing is appended. On error, -1 is returned.

int plugin_path_extend_prefix(PluginInfo *info, const char *prefix, const char *s, const char *pathsep)

Like plugin_paths_extend(), but prefix all relative paths in s with prefix before appending them to paths.

Returns the index of the last appended paths or zero if nothing is appended. On error, -1 is returned.

int plugin_path_remove_index(PluginInfo *info, int index)

Removes path index n from current search path. If n is negative, it counts from the end (like Python).

Returns non-zero on error.

int plugin_path_remove(PluginInfo *info, const char *path)

Removes path path. Returns non-zero if there is no such path.

int plugin_path_index(PluginInfo *info, const char *path)

Returns index of plugin path path or -1 on error.

struct _PluginAPI

#include <plugin.h>

Base declaration of a plugin API that all plugin APIs can be cast into.

struct map_plg_t

#include <plugin.h>

New map types for plugins and plugin apis

Public Members

map_base_t base

Plugin **ref

Plugin *tmp

struct map_api_t

Public Members

map_base_t base

PluginAPI **ref

PluginAPI *tmp

struct _PluginInfo

#include <plugin.h>

Info about a plugin kind

Public Members

const char *kind

Name of this plugin kind

const char *symbol

Name of function in plugin returning the api

const char *envvar

Name of environment variable initialising the plugin search path

void *state

Pointer to global state passed to PluginFunc

FUPaths paths

Current plugin search paths

map_plg_t plugins

Maps plugin paths to loaded plugins

map_str_t pluginpaths

Maps api names to plugin path names

map_api_t apis

Maps api names to plugin apis

struct _PluginIter

#include <plugin.h>

Struct for iterating over registered plugins

Public Members

const PluginInfo *info

map_iter_t miter