src/plugin.h

   1 /* plugin.h -- header file for the generic plugin routines for vlock,
   2  *             the VT locking program for linux
   3  *
   4  * This program is copyright (C) 2007 Frank Benkstein, and is free
   5  * software which is freely distributable under the terms of the
   6  * GNU General Public License version 2, included as the file COPYING in this
   7  * distribution.  It is NOT public domain software, and any
   8  * redistribution not permitted by the GNU General Public License is
   9  * expressly forbidden without prior written permission from
  10  * the author.
  11  *
  12  */
  13
  14 #include <stdbool.h>
  15
  16 /* Names of dependencies plugins may specify. */
  17 #define nr_dependencies 6
  18 extern const char *dependency_names[nr_dependencies];
  19
  20 /* A plugin hook consists of a name and a handler function. */
  21 struct hook
  22 {
  23   const char *name;
  24   void (*handler)(const char *);
  25 };
  26
  27 /* Hooks that a plugin may define. */
  28 #define nr_hooks 4
  29 extern const struct hook hooks[nr_hooks];
  30
  31 struct plugin_type;
  32
  33 /* Struct representing a plugin instance. */
  34 struct plugin
  35 {
  36   /* The name of the plugin. */
  37   char *name;
  38
  39   /* Array of dependencies.  Each dependency is a (possibly empty) list of
  40    * strings.  The dependencies must be stored in the same order as the
  41    * dependency names above.  The strings a freed when the plugin is destroyed
  42    * thus must be stored as copies. */
  43   struct list *dependencies[nr_dependencies];
  44
  45   /* Did one of the save hooks fail? */
  46   bool save_disabled;
  47
  48   /* The type of the plugin. */
  49   struct plugin_type *type;
  50
  51   /* The call_hook and close functions may use this pointer. */
  52   void *context;
  53 };
  54
  55
  56 /* Struct representing the type of a plugin. */
  57 struct plugin_type
  58 {
  59   /* Method that is called on plugin initialization. */
  60   bool (*init)(struct plugin *p);
  61   /* Method that is called on plugin destruction.  */
  62   void (*destroy)(struct plugin *p);
  63   /* Method that is called when a hook should be executed.  */
  64   bool (*call_hook)(struct plugin *p, const char *name);
  65 };
  66
  67 /* Modules. */
  68 extern struct plugin_type *module;
  69 /* Scripts. */
  70 extern struct plugin_type *script;
  71
  72 /* Open a new plugin struct of the given type.  On error errno is set and NULL
  73  * is returned. */
  74 struct plugin *new_plugin(const char *name, struct plugin_type *type);
  75
  76 /* Destroy the given plugin.  This is the opposite of of __allocate_plugin.
  77  * This function should not be called directly. */
  78 void destroy_plugin(struct plugin *p);
  79
  80 /* Call the hook of a plugin. */
  81 bool call_hook(struct plugin *p, const char *hook_name);