jfrEpochQueue.hpp

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#ifndef SHARE_JFR_UTILITIES_JFREPOCHQUEUE_HPP
#define SHARE_JFR_UTILITIES_JFREPOCHQUEUE_HPP

#include "jfr/recorder/storage/jfrEpochStorage.hpp"

/*
 * An ElmentPolicy template template argument provides the implementation for how elements
 * associated with the queue is encoded and managed by exposing the following members:
 *
 *  ElmentPolicy::Type                             the type of the element to be stored in the queue.
 *  size_t element_size(Type* t);                  per element storage size requirement.
 *  void store_element(Type* t, Buffer* buffer);   encode and store element of Type into storage of type Buffer.
 *  Buffer* thread_local_storage(Thread* thread);  quick access to thread local storage.
 *  void set_thread_lcoal_storage(Buffer* buffer, Thread* thread); store back capability for newly acquired storage.
 *
 * The ElementPolicy is also the callback when iterating elements of the queue.
 * The iteration callback signature to be provided by the policy class:
 *
 *  size_t operator()(const u1* next_element, Callback& callback, bool previous_epoch = false);
 */
template <template <typename> class ElementPolicy>
class JfrEpochQueue : public JfrCHeapObj {
 public:
  typedef JfrEpochStorage::Buffer Buffer;
  typedef JfrEpochStorage::BufferPtr BufferPtr;
  typedef typename ElementPolicy<Buffer>::Type Type;
  typedef const Type* TypePtr;
  JfrEpochQueue();
  ~JfrEpochQueue();
  bool initialize(size_t min_buffer_size, size_t free_list_cache_count_limit, size_t cache_prealloc_count);
  void enqueue(TypePtr t);
  template <typename Callback>
  void iterate(Callback& callback, bool previous_epoch = false);
 private:
  typedef ElementPolicy<Buffer> Policy;
  Policy _policy;
  JfrEpochStorage* _storage;
  BufferPtr storage_for_element(TypePtr t, size_t element_size);

  template <typename Callback>
  class ElementDispatch {
   private:
    Callback& _callback;
    Policy& _policy;
   public:
    typedef Buffer Type;
    ElementDispatch(Callback& callback, Policy& policy);
    size_t operator()(const u1* element, bool previous_epoch);
  };
};

#endif // SHARE_JFR_UTILITIES_JFREPOCHQUEUE_HPP