chdir-notify.h

   1 #ifndef CHDIR_NOTIFY_H
   2 #define CHDIR_NOTIFY_H
   3
   4 /*
   5  * An API to let code "subscribe" to changes to the current working directory.
   6  * The general idea is that some code asks to be notified when the working
   7  * directory changes, and other code that calls chdir uses a special wrapper
   8  * that notifies everyone.
   9  */
  10
  11 /*
  12  * Callers who need to know about changes can do:
  13  *
  14  *   void foo(const char *old_path, const char *new_path, void *data)
  15  *   {
  16  *      warning("switched from %s to %s!", old_path, new_path);
  17  *   }
  18  *   ...
  19  *   chdir_notify_register("description", foo, data);
  20  *
  21  * In practice most callers will want to move a relative path to the new root;
  22  * they can use the reparent_relative_path() helper for that. If that's all
  23  * you're doing, you can also use the convenience function:
  24  *
  25  *   chdir_notify_reparent("description", &my_path);
  26  *
  27  * Whenever a chdir event occurs, that will update my_path (if it's relative)
  28  * to adjust for the new cwd by freeing any existing string and allocating a
  29  * new one.
  30  *
  31  * Registered functions are called in the order in which they were added. Note
  32  * that there's currently no way to remove a function, so make sure that the
  33  * data parameter remains valid for the rest of the program.
  34  *
  35  * The "name" argument is used only for printing trace output from
  36  * $GIT_TRACE_SETUP. It may be NULL, but if non-NULL should point to
  37  * storage which lasts as long as the registration is active.
  38  */
  39 typedef void (*chdir_notify_callback)(const char *name,
  40                                       const char *old_cwd,
  41                                       const char *new_cwd,
  42                                       void *data);
  43 void chdir_notify_register(const char *name, chdir_notify_callback cb, void *data);
  44 void chdir_notify_reparent(const char *name, char **path);
  45
  46 /*
  47  *
  48  * Callers that want to chdir:
  49  *
  50  *   chdir_notify(new_path);
  51  *
  52  * to switch to the new path and notify any callbacks.
  53  *
  54  * Note that you don't need to chdir_notify() if you're just temporarily moving
  55  * to a directory and back, as long as you don't call any subscribed code in
  56  * between (but it should be safe to do so if you're unsure).
  57  */
  58 int chdir_notify(const char *new_cwd);
  59
  60 /*
  61  * Reparent a relative path from old_root to new_root. For example:
  62  *
  63  *   reparent_relative_path("/a", "/a/b", "b/rel");
  64  *
  65  * would return the (newly allocated) string "rel". Note that we may return an
  66  * absolute path in some cases (e.g., if the resulting path is not inside
  67  * new_cwd).
  68  */
  69 char *reparent_relative_path(const char *old_cwd,
  70                              const char *new_cwd,
  71                              const char *path);
  72
  73 #endif /* CHDIR_NOTIFY_H */