Add free-function retire

[folly.git] / folly / experimental / hazptr / hazptr.h

diff --git a/folly/experimental/hazptr/hazptr.h b/folly/experimental/hazptr/hazptr.h
index f1776e4b8e4c8fd4e9abf4a8edcc1a32d9360b94..48e8392ae48676fccd311e667e41e0f986ca2117 100644 (file)
--- a/folly/experimental/hazptr/hazptr.h
+++ b/folly/experimental/hazptr/hazptr.h
@@ -34,6 +34,12 @@ class hazptr_obj;
 template <typename T, typename Deleter>
 class hazptr_obj_base;
 
+/** hazptr_obj_base_refcounted:
+ *  Base template for reference counted objects protected by hazard pointers.
+ */
+template <typename T, typename Deleter>
+class hazptr_obj_base_refcounted;
+
 /** hazptr_local: Optimized template for bulk construction and destruction of
  *  hazard pointers */
 template <size_t M>
@@ -56,10 +62,16 @@ class hazptr_domain {
   hazptr_domain& operator=(const hazptr_domain&) = delete;
   hazptr_domain& operator=(hazptr_domain&&) = delete;
 
+  /** Free-function retire.  May allocate memory */
+  template <typename T, typename D = std::default_delete<T>>
+  void retire(T* obj, D reclaim = {});
+
  private:
   friend class hazptr_holder;
   template <typename, typename>
   friend class hazptr_obj_base;
+  template <typename, typename>
+  friend class hazptr_obj_base_refcounted;
   friend struct hazptr_priv;
 
   memory_resource* mr_;
@@ -82,15 +94,22 @@ hazptr_domain& default_hazptr_domain();
 
 extern hazptr_domain default_domain_;
 
+/** Free-function retire, that operates on the default domain */
+template <typename T, typename D = std::default_delete<T>>
+void hazptr_retire(T* obj, D reclaim = {});
+
 /** Definition of hazptr_obj */
 class hazptr_obj {
   friend class hazptr_domain;
   template <typename, typename>
   friend class hazptr_obj_base;
+  template <typename, typename>
+  friend class hazptr_obj_base_refcounted;
   friend struct hazptr_priv;
 
   void (*reclaim_)(hazptr_obj*);
   hazptr_obj* next_;
+
   const void* getObjPtr() const;
 };
 
@@ -106,6 +125,33 @@ class hazptr_obj_base : public hazptr_obj {
   D deleter_;
 };
 
+/** Definition of hazptr_recounted_obj_base */
+template <typename T, typename D = std::default_delete<T>>
+class hazptr_obj_base_refcounted : public hazptr_obj {
+ public:
+  /* Retire a removed object and pass the responsibility for
+   * reclaiming it to the hazptr library */
+  void retire(hazptr_domain& domain = default_hazptr_domain(), D reclaim = {});
+
+  /* aquire_ref() increments the reference count
+   *
+   * acquire_ref_safe() is the same as acquire_ref() except that in
+   * addition the caller guarantees that the call is made in a
+   * thread-safe context, e.g., the object is not yet shared. This is
+   * just an optimization to save an atomic operation.
+   *
+   * release_ref() decrements the reference count and returns true if
+   * the object is safe to reclaim.
+   */
+  void acquire_ref();
+  void acquire_ref_safe();
+  bool release_ref();
+
+ private:
+  std::atomic<uint32_t> refcount_{0};
+  D deleter_;
+};
+
 /** hazptr_holder: Class for automatic acquisition and release of
  *  hazard pointers, and interface for hazard pointer operations. */
 class hazptr_holder {