path: root/ace/Timer_Heap.cpp

// Timer_Heap.cpp
// $Id$

#define ACE_BUILD_DLL
#include "ace/Timer_Heap.h"

ACE_Timer_Heap_Iterator::ACE_Timer_Heap_Iterator (ACE_Timer_Heap &heap)
  : timer_heap_ (heap)
{
  ACE_TRACE ("ACE_Timer_Heap_Iterator::ACE_Timer_Heap_Iterator");
}

int
ACE_Timer_Heap_Iterator::next (ACE_Timer_Node *&node,
                               const ACE_Time_Value &cur_time)
{
  ACE_TRACE ("ACE_Timer_Heap_Iterator::next");

  if (this->timer_heap_.cur_size_ == 0 
      || this->timer_heap_.heap_[0]->timer_value_ > cur_time)
    return 0;
  else
    {
      // Remove the first item and restore the heap property.

      node = this->timer_heap_.remove (0);
      return 1;
    }
}

ACE_Timer_Heap::ACE_Timer_Heap (size_t size,
				int preallocate)
  : max_size_ (size),
    cur_size_ (0),
    iterator_ (*this),
    timer_ids_freelist_ (0),
    preallocated_nodes_ (0),
    preallocated_nodes_freelist_ (0)
{
  ACE_TRACE ("ACE_Timer_Heap::ACE_Timer_Heap");

  // Create the heap array.
  ACE_NEW (this->heap_, ACE_Timer_Node *[size]);

  // Create the parallel 
  ACE_NEW (this->timer_ids_, int[size]);

  // Initialize the "freelist," which uses negative values to
  // distinguish freelist elements from "pointers" into the <heap_>
  // array.
  for (size_t i = 0; i < size; i++)
    this->timer_ids_[i] = -(i + 1);

  if (preallocate)
    {
      ACE_NEW (this->preallocated_nodes_,
	       ACE_Timer_Node[size]);
      
      // Form the freelist by linking the next_ pointers together.
      for (size_t j = 1; j < size; j++)
	this->preallocated_nodes_[j - 1].next_ = 
	  &this->preallocated_nodes_[j];

      // NULL-terminate the freelist.
      this->preallocated_nodes_[size - 1].next_ = 0;

      // Assign the freelist pointer to the front of the list.
      this->preallocated_nodes_freelist_ = 
	&this->preallocated_nodes_[0];
    }
}

ACE_Timer_Heap::~ACE_Timer_Heap (void)
{
  ACE_TRACE ("ACE_Timer_Heap::~ACE_Timer_Heap");
  delete [] this->heap_;
  delete [] this->timer_ids_;
  delete [] this->preallocated_nodes_;
}

int
ACE_Timer_Heap::pop_freelist (void)
{
  ACE_TRACE ("ACE_Timer_Heap::pop_freelist");

  int new_id = this->timer_ids_freelist_;
  // The freelist values in the <timer_ids_> are negative, so we need
  // to negate them to get the next freelist "pointer."
  this->timer_ids_freelist_ = -this->timer_ids_[this->timer_ids_freelist_];
  return new_id;
}

void
ACE_Timer_Heap::push_freelist (int old_id)
{
  ACE_TRACE ("ACE_Timer_Heap::push_freelist");

  // The freelist values in the <timer_ids_> are negative, so we need
  // to negate them to get the next freelist "pointer."
  this->timer_ids_[old_id] = -this->timer_ids_freelist_;
  this->timer_ids_freelist_ = old_id;
}

int
ACE_Timer_Heap::timer_id (void)
{
  ACE_TRACE ("ACE_Timer_Heap::timer_id");

  // Return the next item off the freelist and use it as the timer id.
  return this->pop_freelist ();
}

// Checks if queue is empty. 

int 
ACE_Timer_Heap::is_empty (void) const
{
  ACE_TRACE ("ACE_Timer_Heap::is_empty");
  return this->cur_size_ == 0;
}

ACE_Timer_Queue_Iterator &
ACE_Timer_Heap::get_iterator (void)
{
  return this->iterator_;
}

// Returns earliest time in a non-empty queue.

const ACE_Time_Value &
ACE_Timer_Heap::earliest_time (void) const
{
  ACE_TRACE ("ACE_Timer_Heap::earliest_time");
  return this->heap_[0]->timer_value_;
}

void
ACE_Timer_Heap::dump (void) const
{
  ACE_TRACE ("ACE_Timer_Heap::dump");
  ACE_DEBUG ((LM_DEBUG, ACE_BEGIN_DUMP, this));

  ACE_DEBUG ((LM_DEBUG, "\nmax_size_ = %d", this->max_size_));
  ACE_DEBUG ((LM_DEBUG, "\ncur_size_ = %d", this->cur_size_));
  ACE_DEBUG ((LM_DEBUG, "\nheap_ = \n"));

  for (size_t i = 0; i < this->cur_size_; i++)
    {
      ACE_DEBUG ((LM_DEBUG, "%d\n", i));
      this->heap_[i]->dump ();
    }

  ACE_DEBUG ((LM_DEBUG, "\ntimer_ids_ = \n"));

  for (size_t j = 0; j < this->cur_size_; j++)
    ACE_DEBUG ((LM_DEBUG, "%d\t%d\n", j, this->timer_ids_[j]));

  ACE_DEBUG ((LM_DEBUG, ACE_END_DUMP));
}

ACE_Timer_Node *
ACE_Timer_Heap::remove (size_t index)
{
  ACE_Timer_Node *result = this->heap_[index];

  // Return this timer id to the freelist.
  this->push_freelist (result->timer_id_);

  // Decrement the size of the heap by one since we're removing the
  // "index"th node.
  this->cur_size_--;

  // Only try to reheapify if we're not deleting the last entry.
  
  if (index < this->cur_size_)
    {
      // Move the end node to the location being removed.
      this->heap_[index] = this->heap_[this->cur_size_];

      // Update the corresponding slot in the parallel <timer_ids>
      // array.
      this->timer_ids_[this->heap_[this->cur_size_]->timer_id_] = index;

      ACE_Timer_Node *moved_node = this->heap_[index];

      // If we're at the top there's no place to go but down!
      if (index == 0)
        this->reheap_down (moved_node, 1);

      // If the moved_node->time_value_ is smaller than its parent it
      // needs be moved up the heap.
      else if (moved_node->timer_value_ < this->heap_[(index - 1) / 2]->timer_value_)
        this->reheap_up (moved_node);

      // Call <reheap_down>, which will reheapify if the
      // moved_node->time_value_ is larger than either of its children
      // (who start at location <index + index>).
      else
        this->reheap_down (moved_node, index + index);
    }

  return result;
}

void
ACE_Timer_Heap::reheap_down (ACE_Timer_Node *moved_node,
                             size_t child_index)
{
  int parent = 0;

  // Restore the heap property after a deletion.

  for (size_t child = child_index; 
       child < this->cur_size_;
       child += child + 1) // Multiple child by 2 and add 1.
    {
      // Choose the smaller of the two children.
      if (child + 1 < this->cur_size_
          && this->heap_[child + 1]->timer_value_ < this->heap_[child]->timer_value_)
        child++;

      // Perform a swap if the child has a larger timeout value than
      // the front node.
      if (this->heap_[child]->timer_value_ < moved_node->timer_value_)
        {
	  // Insert the child node into its new location in the heap.
          this->heap_[parent] = this->heap_[child];

	  // Update the corresponding slot in the parallel <timer_ids>
	  // array.
	  this->timer_ids_[this->heap_[child]->timer_id_] = parent;

          parent = child;
        }
      else 
        break; 
    }

  // Insert moved_node into its final resting place.
  this->heap_[parent] = moved_node;   

  // Update the corresponding slot in the parallel <timer_ids>
  // array.
  this->timer_ids_[moved_node->timer_id_] = parent;
}

void
ACE_Timer_Heap::insert (ACE_Timer_Node *new_node)
{
  this->reheap_up (new_node);
  this->cur_size_++;
}

void
ACE_Timer_Heap::reheap_up (ACE_Timer_Node *new_node)
{
  int parent;
  int child = this->cur_size_;

  // Restore the heap property after an insertion.

  while (child > 0) 
    {
      parent = (child - 1) / 2;

      // If the parent node is great than the new node we need to swap
      // them.
      if (new_node->timer_value_ < this->heap_[parent]->timer_value_)
        {
	  // Insert the parent node into its new location in the heap.
          this->heap_[child] = this->heap_[parent];

	  // Update the corresponding slot in the parallel <timer_ids>
	  // array.
	  this->timer_ids_[this->heap_[parent]->timer_id_] = child;
          child = parent;
        }
      else 
        break;
    }

  // Insert the new node into its proper resting place in the heap.
  this->heap_[child] = new_node;

  // Update the corresponding slot in the parallel <timer_ids> array.
  this->timer_ids_[new_node->timer_id_] = child;
}

// Reschedule a periodic timer.  This function must be called with the
// mutex lock held.

void 
ACE_Timer_Heap::reschedule (ACE_Timer_Node *expired)
{
  ACE_TRACE ("ACE_Timer_Heap::reschedule");

  // Restore the heap property.
  this->insert (expired);
}

ACE_Timer_Node *
ACE_Timer_Heap::alloc_node (void)
{
  ACE_Timer_Node *temp;

  // Only allocate a node if we are *not* using the preallocated heap.
  if (this->preallocated_nodes_ == 0)
    ACE_NEW_RETURN (temp,
		    ACE_Timer_Node,
		    0);
  else
    {
      temp = this->preallocated_nodes_freelist_;

      // Remove the element from the freelist.
      this->preallocated_nodes_freelist_ = 
	this->preallocated_nodes_freelist_->next_;
    }
  return temp;
}

void
ACE_Timer_Heap::free_node (ACE_Timer_Node *node)
{
  // Only free up a node if we are *not* using the preallocated heap.
  if (this->preallocated_nodes_ == 0)
    delete node;
  else
    {
      node->next_ = this->preallocated_nodes_freelist_;
      this->preallocated_nodes_freelist_ = node;
    }
}

// Insert a new handler that expires at time future_time; if interval
// is > 0, the handler will be reinvoked periodically.

int
ACE_Timer_Heap::schedule (ACE_Event_Handler *handler,
                          const void *arg,
                          const ACE_Time_Value &future_time, 
                          const ACE_Time_Value &interval)
{
  ACE_TRACE ("ACE_Timer_Heap::schedule");

  ACE_MT (ACE_GUARD_RETURN (ACE_Recursive_Thread_Mutex, ace_mon, this->lock_, -1));

  if (this->cur_size_ < this->max_size_)
    {
      // Obtain the next unique sequence number.
      int timer_id = this->timer_id ();

      // Obtain the memory to the new node.
      ACE_Timer_Node *temp = this->alloc_node ();

      if (temp)
	{
	  // Use operator placement new.
	  new (temp) ACE_Timer_Node (handler, 
				     arg, 
				     future_time,
				     interval, 
				     0,
				     timer_id);
	  this->insert (temp);
	  return timer_id;
	}
    }
  // Failure return.
  errno = ENOMEM;
  return -1;
}

// Locate and remove the single <ACE_Event_Handler> with a value of
// <timer_id> from the timer queue.

int
ACE_Timer_Heap::cancel (int timer_id, 
                        const void **arg)
{
  ACE_TRACE ("ACE_Timer_Heap::cancel");
  ACE_MT (ACE_GUARD_RETURN (ACE_Recursive_Thread_Mutex, ace_mon, this->lock_, -1));

  // Locate the ACE_Timer_Node that corresponds to the timer_id.

  int timer_node_slot = this->timer_ids_[timer_id];

  if (timer_id != this->heap_[timer_node_slot]->timer_id_)
    {
      ACE_ASSERT (timer_id == this->heap_[timer_node_slot]->timer_id_);
      return 0;
    }
  else
    {
      ACE_Timer_Node *temp = this->remove (timer_node_slot);

      if (arg != 0)
        *arg = temp->arg_;

      this->free_node (temp);
      return 1;
    }
}

// Locate and remove all values of <handler> from the timer queue.

int
ACE_Timer_Heap::cancel (ACE_Event_Handler *handler)
{
  ACE_TRACE ("ACE_Timer_Heap::cancel");
  ACE_MT (ACE_GUARD_RETURN (ACE_Recursive_Thread_Mutex, ace_mon, this->lock_, -1));

  int number_of_cancellations = 0;

  // Try to locate the ACE_Timer_Node that matches the timer_id.

  for (size_t i = 0; 
       i < this->cur_size_;
       )
    {
      if (this->heap_[i]->handler_ == handler)
        {
          ACE_Timer_Node *temp = this->remove (i);
          this->free_node (temp);
          number_of_cancellations++;
        }
      else
       i++;
    }

  return number_of_cancellations;
}