src/include/gpxe/refcnt.h

   1 #ifndef _GPXE_REFCNT_H
   2 #define _GPXE_REFCNT_H
   3
   4 /** @file
   5  *
   6  * Reference counting
   7  *
   8  */
   9
  10 FILE_LICENCE ( GPL2_OR_LATER );
  11
  12 /**
  13  * A reference counter
  14  *
  15  * This data structure is designed to be embedded within a
  16  * reference-counted object.
  17  *
  18  * Reference-counted objects are freed when their reference count
  19  * drops below zero.  This means that a freshly allocated-and-zeroed
  20  * reference-counted object will be freed on the first call to
  21  * ref_put().
  22  */
  23 struct refcnt {
  24         /** Current reference count
  25          *
  26          * When this count is decremented below zero, the free()
  27          * method will be called.
  28          */
  29         int refcnt;
  30         /** Free containing object
  31          *
  32          * This method is called when the reference count is
  33          * decremented below zero.
  34          *
  35          * If this method is left NULL, the standard library free()
  36          * function will be called.  The upshot of this is that you
  37          * may omit the free() method if the @c refcnt object is the
  38          * first element of your reference-counted struct.
  39          */
  40         void ( * free ) ( struct refcnt *refcnt );
  41 };
  42
  43 extern struct refcnt * ref_get ( struct refcnt *refcnt );
  44 extern void ref_put ( struct refcnt *refcnt );
  45
  46 #endif /* _GPXE_REFCNT_H */