mono/utils/refcount.h

   1 /**
   2  * \file
   3  */
   4
   5 #ifndef __MONO_UTILS_REFCOUNT_H__
   6 #define __MONO_UTILS_REFCOUNT_H__
   7
   8 #include <glib.h>
   9 #include <config.h>
  10
  11 #include "atomic.h"
  12
  13 /*
  14  * Mechanism for ref-counting which tries to be as user-friendly as possible. Instead of being a wrapper around
  15  * user-provided data, it is embedded into the user data.
  16  *
  17  * This introduces some constraints on the MonoRefCount field:
  18  *  - it needs to be called "ref"
  19  *  - it cannot be a pointer
  20  */
  21
  22 typedef struct {
  23         guint32 ref;
  24         void (*destructor) (gpointer data);
  25 } MonoRefCount;
  26
  27 #define mono_refcount_init(v,destructor) do { mono_refcount_initialize (&(v)->ref, (destructor)); } while (0)
  28 #define mono_refcount_inc(v) (mono_refcount_increment (&(v)->ref),(v))
  29 #define mono_refcount_tryinc(v) (mono_refcount_tryincrement (&(v)->ref))
  30 #define mono_refcount_dec(v) (mono_refcount_decrement (&(v)->ref))
  31
  32 static inline void
  33 mono_refcount_initialize (MonoRefCount *refcount, void (*destructor) (gpointer data))
  34 {
  35         refcount->ref = 1;
  36         refcount->destructor = destructor;
  37 }
  38
  39 static inline gboolean
  40 mono_refcount_tryincrement (MonoRefCount *refcount)
  41 {
  42         guint32 oldref, newref;
  43
  44         g_assert (refcount);
  45
  46         do {
  47                 oldref = refcount->ref;
  48                 if (oldref == 0)
  49                         return FALSE;
  50
  51                 newref = oldref + 1;
  52         } while (mono_atomic_cas_i32 ((gint32*) &refcount->ref, (gint32)newref, (gint32)oldref) != (gint32)oldref);
  53
  54         return TRUE;
  55 }
  56
  57 static inline void
  58 mono_refcount_increment (MonoRefCount *refcount)
  59 {
  60         if (!mono_refcount_tryincrement (refcount))
  61                 g_error ("%s: cannot increment a ref with value 0", __func__);
  62 }
  63
  64 static inline guint32
  65 mono_refcount_decrement (MonoRefCount *refcount)
  66 {
  67         guint32 oldref, newref;
  68
  69         g_assert (refcount);
  70
  71         do {
  72                 oldref = refcount->ref;
  73                 if (oldref == 0)
  74                         g_error ("%s: cannot decrement a ref with value 0", __func__);
  75
  76                 newref = oldref - 1;
  77         } while (mono_atomic_cas_i32 ((gint32*) &refcount->ref, (gint32)newref, (gint32)oldref) != (gint32)oldref);
  78
  79         if (newref == 0 && refcount->destructor)
  80                 refcount->destructor ((gpointer) refcount);
  81
  82         return newref;
  83 }
  84
  85 #endif /* __MONO_UTILS_REFCOUNT_H__ */