ACE/ace/Timer_Heap_T.h

   1 // -*- C++ -*-
   2
   3 //=============================================================================
   4 /**
   5  *  @file    Timer_Heap_T.h
   6  *
   7  *  @author Douglas C. Schmidt <d.schmidt@vanderbilt.edu>
   8  */
   9 //=============================================================================
  10
  11 #ifndef ACE_TIMER_HEAP_T_H
  12 #define ACE_TIMER_HEAP_T_H
  13 #include /**/ "ace/pre.h"
  14
  15 #include "ace/Timer_Queue_T.h"
  16
  17 #if !defined (ACE_LACKS_PRAGMA_ONCE)
  18 # pragma once
  19 #endif /* ACE_LACKS_PRAGMA_ONCE */
  20
  21 #include "ace/Free_List.h"
  22 #include "ace/Unbounded_Set.h"
  23
  24 ACE_BEGIN_VERSIONED_NAMESPACE_DECL
  25
  26 // Forward declaration
  27 template <class TYPE, class FUNCTOR, class ACE_LOCK, typename TIME_POLICY>
  28 class ACE_Timer_Heap_T;
  29
  30 /**
  31  * @class ACE_Timer_Heap_Iterator_T
  32  *
  33  * @brief Iterates over an ACE_Timer_Heap_T.
  34  *
  35  * This is a generic iterator that can be used to visit every
  36  * node of a timer queue.  Be aware that it doesn't transverse
  37  * in the order of timeout values.
  38  */
  39 template <class TYPE, class FUNCTOR, class ACE_LOCK, typename TIME_POLICY = ACE_Default_Time_Policy>
  40 class ACE_Timer_Heap_Iterator_T : public ACE_Timer_Queue_Iterator_T<TYPE>
  41 {
  42 public:
  43   typedef ACE_Timer_Heap_T<TYPE, FUNCTOR, ACE_LOCK, TIME_POLICY> Heap;
  44   /// Constructor.
  45   ACE_Timer_Heap_Iterator_T (Heap &);
  46
  47   /// Destructor.
  48   ~ACE_Timer_Heap_Iterator_T () override = default;
  49
  50   /// Positions the iterator at the earliest node in the Timer Queue
  51   void first () override;
  52
  53   /// Positions the iterator at the next node in the Timer Queue
  54   void next () override;
  55
  56   /// Returns true when there are no more nodes in the sequence
  57   bool isdone () const override;
  58
  59   /// Returns the node at the current position in the sequence
  60   ACE_Timer_Node_T<TYPE> *item () override;
  61
  62   /// Declare the dynamic allocation hooks.
  63   ACE_ALLOC_HOOK_DECLARE;
  64
  65 protected:
  66   /// Pointer to the ACE_Timer_Heap that we are iterating over.
  67   Heap & timer_heap_;
  68
  69   /// Position in the array where the iterator is at
  70   size_t position_;
  71 };
  72
  73 /**
  74  * @class ACE_Timer_Heap_T
  75  *
  76  * @brief Provides a very fast and predictable timer implementation.
  77  *
  78  * This implementation uses a heap-based callout queue of
  79  * absolute times.  Therefore, in the average and worst case,
  80  * scheduling, canceling, and expiring timers is O(log N) (where
  81  * N is the total number of timers).  In addition, we can also
  82  * preallocate as many @c ACE_Timer_Node objects as there are slots
  83  * in the heap.  This allows us to completely remove the need for
  84  * dynamic memory allocation, which is important for real-time
  85  * systems.
  86  */
  87 template <class TYPE, class FUNCTOR, class ACE_LOCK, typename TIME_POLICY = ACE_Default_Time_Policy>
  88 class ACE_Timer_Heap_T : public ACE_Timer_Queue_T<TYPE, FUNCTOR, ACE_LOCK, TIME_POLICY>
  89 {
  90 public:
  91   typedef ACE_Timer_Heap_Iterator_T<TYPE, FUNCTOR, ACE_LOCK, TIME_POLICY> HEAP_ITERATOR;
  92   friend class ACE_Timer_Heap_Iterator_T<TYPE, FUNCTOR, ACE_LOCK, TIME_POLICY>;
  93
  94   typedef ACE_Timer_Queue_T<TYPE, FUNCTOR, ACE_LOCK, TIME_POLICY> Base_Time_Policy;
  95
  96   /**
  97    * The Constructor creates a heap with specified number of elements.
  98    * This can also take in a upcall functor and freelist (if 0, then
  99    * defaults will be created).
 100    *
 101    * @param size The maximum number of timers that can be
 102    * inserted into the new object.
 103    * @param preallocated Default false, true then all the memory
 104    * for the @c ACE_Timer_Node objects will be pre-allocated. This saves
 105    * time and is more predictable (though it requires more space).
 106    * Otherwise, timer nodes are allocated as needed.
 107    * @param freelist is the freelist of timer nodes.
 108    * @param upcall_functor If 0 Timer Heap will create a default FUNCTOR.
 109    */
 110   ACE_Timer_Heap_T (size_t size,
 111                     bool preallocated = false,
 112                     FUNCTOR *upcall_functor = 0,
 113                     ACE_Free_List<ACE_Timer_Node_T <TYPE> > *freelist = 0,
 114                     TIME_POLICY const & time_policy = TIME_POLICY());
 115
 116   /**
 117    * Default constructor. @c upcall_functor is the instance of the
 118    * FUNCTOR to be used by the queue. If @c upcall_functor is 0, Timer
 119    * Heap will create a default FUNCTOR.  @c freelist is the freelist of
 120    * timer nodes.  If 0, then a default freelist will be created.  The default
 121    * size will be ACE_DEFAULT_TIMERS and there will be no preallocation.
 122    */
 123   ACE_Timer_Heap_T (FUNCTOR *upcall_functor = 0,
 124                     ACE_Free_List<ACE_Timer_Node_T <TYPE> > *freelist = 0,
 125                     TIME_POLICY const & time_policy = TIME_POLICY());
 126
 127   /// Destructor.
 128   virtual ~ACE_Timer_Heap_T ();
 129
 130   /// True if heap is empty, else false.
 131   virtual bool is_empty () const;
 132
 133   /// Returns the time of the earliest node in the Timer_Queue.
 134   /// Must be called on a non-empty queue.
 135   virtual const ACE_Time_Value &earliest_time () const;
 136
 137   /**
 138    * Resets the interval of the timer represented by @a timer_id to
 139    * @a interval, which is specified in relative time to the current
 140    * <gettimeofday>.  If @a interval is equal to
 141    * ACE_Time_Value::zero, the timer will become a non-rescheduling
 142    * timer.  Returns 0 if successful, -1 if not.
 143    */
 144   virtual int reset_interval (long timer_id,
 145                               const ACE_Time_Value &interval);
 146
 147   /**
 148    * Cancel all timers associated with @a type.  If @a dont_call_handle_close
 149    * is 0 then the <functor> will be invoked.  Returns number of timers
 150    * cancelled.
 151    */
 152   virtual int cancel (const TYPE &type,
 153                       int dont_call_handle_close = 1);
 154
 155   /**
 156    * Cancel the single timer that matches the @a timer_id value (which
 157    * was returned from the <schedule> method).  If act is non-NULL
 158    * then it will be set to point to the ``magic cookie'' argument
 159    * passed in when the timer was registered.  This makes it possible
 160    * to free up the memory and avoid memory leaks. If @a dont_call_handle_close
 161    * is 0 then the <functor> will be invoked.  Returns 1 if cancellation
 162    * succeeded and 0 if the @a timer_id wasn't found.
 163    */
 164   virtual int cancel (long timer_id,
 165                       const void **act = 0,
 166                       int dont_call_handle_close = 1);
 167
 168   /**
 169    * Destroy timer queue. Cancels all timers.
 170    */
 171   virtual int close ();
 172
 173   /// Returns a pointer to this ACE_Timer_Queue's iterator.
 174   virtual ACE_Timer_Queue_Iterator_T<TYPE> &iter ();
 175
 176   /**
 177    * Removes the earliest node from the queue and returns it. Note that
 178    * the timer is removed from the heap, but is not freed, and its ID
 179    * is not reclaimed. The caller is responsible for calling either
 180    * @c reschedule() or @c free_node() after this function returns. Thus,
 181    * this function is for support of @c ACE_Timer_Queue::expire and
 182    * should not be used unadvisedly in other conditions.
 183    */
 184   ACE_Timer_Node_T <TYPE> *remove_first ();
 185
 186   /// Dump the state of an object.
 187   virtual void dump () const;
 188
 189   /// Reads the earliest node from the queue and returns it.
 190   virtual ACE_Timer_Node_T<TYPE> *get_first ();
 191
 192   /// Declare the dynamic allocation hooks.
 193   ACE_ALLOC_HOOK_DECLARE;
 194
 195 protected:
 196   /**
 197    * Schedule a timer that may optionally auto-reset.
 198    * Schedule @a type that will expire at @a future_time,
 199    * which is specified in absolute time.  If it expires then @a act is
 200    * passed in as the value to the <functor>.  If @a interval is != to
 201    * ACE_Time_Value::zero then it is used to reschedule the @a type
 202    * automatically, using relative time to the current <gettimeofday>.
 203    * This method returns a <timer_id> that uniquely identifies the the
 204    * @a type entry in an internal list.  This <timer_id> can be used to
 205    * cancel the timer before it expires.  The cancellation ensures
 206    * that <timer_ids> are unique up to values of greater than 2
 207    * billion timers.  As long as timers don't stay around longer than
 208    * this there should be no problems with accidentally deleting the
 209    * wrong timer.  Returns -1 on failure (which is guaranteed never to
 210    * be a valid <timer_id>).
 211    */
 212   virtual long schedule_i (const TYPE &type,
 213                            const void *act,
 214                            const ACE_Time_Value &future_time,
 215                            const ACE_Time_Value &interval);
 216
 217   /// Reschedule an "interval" ACE_Timer_Node.
 218   virtual void reschedule (ACE_Timer_Node_T<TYPE> *);
 219
 220   /// Factory method that allocates a new node (uses operator new if
 221   /// we're *not* preallocating, otherwise uses an internal freelist).
 222   virtual ACE_Timer_Node_T<TYPE> *alloc_node ();
 223
 224   /**
 225    * Factory method that frees a previously allocated node (uses
 226    * operator delete if we're *not* preallocating, otherwise uses an
 227    * internal freelist).
 228    */
 229   virtual void free_node (ACE_Timer_Node_T<TYPE> *);
 230
 231 private:
 232   /// Remove and return the @a sloth ACE_Timer_Node and restore the
 233   /// heap property.
 234   ACE_Timer_Node_T<TYPE> *remove (size_t slot);
 235
 236   /// Insert @a new_node into the heap and restore the heap property.
 237   void insert (ACE_Timer_Node_T<TYPE> *new_node);
 238
 239   /**
 240    * Doubles the size of the heap and the corresponding timer_ids array.
 241    * If preallocation is used, will also double the size of the
 242    * preallocated array of ACE_Timer_Nodes.
 243    */
 244   void grow_heap ();
 245
 246   /// Restore the heap property, starting at @a slot.
 247   void reheap_up (ACE_Timer_Node_T<TYPE> *new_node,
 248                   size_t slot,
 249                   size_t parent);
 250
 251   /// Restore the heap property, starting at @a slot.
 252   void reheap_down (ACE_Timer_Node_T<TYPE> *moved_node,
 253                     size_t slot,
 254                     size_t child);
 255
 256   /// Copy @a moved_node into the @a slot slot of <heap_> and move
 257   /// @a slot into the corresponding slot in the <timer_id_> array.
 258   void copy (size_t slot, ACE_Timer_Node_T<TYPE> *moved_node);
 259
 260   /**
 261    * Returns a timer id that uniquely identifies this timer.  This id
 262    * can be used to cancel a timer via the <cancel (int)> method.  The
 263    * timer id returned from this method will never == -1 to avoid
 264    * conflicts with other failure return values.
 265    */
 266   long timer_id ();
 267
 268   /// Pops and returns a new timer id from the freelist.
 269   long pop_freelist ();
 270
 271   /// Pushes @a old_id onto the freelist.
 272   void push_freelist (long old_id);
 273
 274   /// Maximum size of the heap.
 275   size_t max_size_;
 276
 277   /// Current size of the heap.
 278   size_t cur_size_;
 279
 280   /// Number of heap entries in transition (removed from the queue, but
 281   /// not freed) and may be rescheduled or freed.
 282   size_t cur_limbo_;
 283
 284   /// Iterator used to expire timers.
 285   HEAP_ITERATOR *iterator_;
 286
 287   /**
 288    * Current contents of the Heap, which is organized as a "heap" of
 289    * ACE_Timer_Node *'s.  In this context, a heap is a "partially
 290    * ordered, almost complete" binary tree, which is stored in an
 291    * array.
 292    */
 293   ACE_Timer_Node_T<TYPE> **heap_;
 294
 295   /**
 296    * An array of "pointers" that allows each ACE_Timer_Node in the
 297    * <heap_> to be located in O(1) time.  Basically, <timer_id_[i]>
 298    * contains the slot in the <heap_> array where an ACE_Timer_Node
 299    * * with timer id \<i\> resides.  Thus, the timer id passed back from
 300    * <schedule> is really a slot into the <timer_ids> array.  The
 301    * <timer_ids_> array serves two purposes: negative values are
 302    * indications of free timer IDs, whereas positive values are
 303    * "pointers" into the <heap_> array for assigned timer IDs.
 304    */
 305   ssize_t *timer_ids_;
 306
 307   /// "Pointer" to the element in the <timer_ids_> array that was
 308   /// last given out as a timer ID.
 309   size_t timer_ids_curr_;
 310
 311   /// Index representing the lowest timer ID that has been freed. When
 312   /// the timer_ids_next_ value wraps around, it starts back at this
 313   /// point.
 314   size_t timer_ids_min_free_;
 315
 316   /**
 317    * If this is non-0, then we preallocate <max_size_> number of
 318    * ACE_Timer_Node objects in order to reduce dynamic allocation
 319    * costs.  In auto-growing implementation, this points to the
 320    * last array of nodes allocated.
 321    */
 322   ACE_Timer_Node_T<TYPE> *preallocated_nodes_;
 323
 324   /// This points to the head of the <preallocated_nodes_> freelist,
 325   /// which is organized as a stack.
 326   ACE_Timer_Node_T<TYPE> *preallocated_nodes_freelist_;
 327
 328   /// Set of pointers to the arrays of preallocated timer nodes.
 329   /// Used to delete the allocated memory when required.
 330   ACE_Unbounded_Set<ACE_Timer_Node_T<TYPE> *> preallocated_node_set_;
 331 };
 332
 333 ACE_END_VERSIONED_NAMESPACE_DECL
 334
 335 #include "ace/Timer_Heap_T.cpp"
 336
 337 #include /**/ "ace/post.h"
 338 #endif /* ACE_TIMER_HEAP_T_H */