text: 
  #if !defined(MEDUSA_MONITOR_PRIVATE_H)
  #define MEDUSA_MONITOR_PRIVATE_H
  
  struct medusa_subject;
  struct medusa_monitor;
  
  int medusa_monitor_lock (struct medusa_monitor *monitor);
  int medusa_monitor_unlock (struct medusa_monitor *monitor);
  
  int medusa_monitor_add (struct medusa_monitor *monitor, struct medusa_subject *subject);
  int medusa_monitor_mod (struct medusa_subject *subject);
  int medusa_monitor_del (struct medusa_subject *subject);
  
  int medusa_monitor_add_unlocked (struct medusa_monitor *monitor, struct medusa_subject *subject);
  int medusa_monitor_mod_unlocked (struct medusa_subject *subject);
  int medusa_monitor_del_unlocked (struct medusa_subject *subject);
  
  #endif
  