LCOV - code coverage report
Current view: directory - objdir/dist/include - nsTPriorityQueue.h (source / functions) Found Hit Coverage
Test: app.info Lines: 49 0 0.0 %
Date: 2012-06-02 Functions: 10 0 0.0 %

       1                 : /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
       2                 : /* vim:set ts=2 sw=2 sts=2 et cindent: */
       3                 : /* ***** BEGIN LICENSE BLOCK *****
       4                 :  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
       5                 :  *
       6                 :  * The contents of this file are subject to the Mozilla Public License Version
       7                 :  * 1.1 (the "License"); you may not use this file except in compliance with
       8                 :  * the License. You may obtain a copy of the License at
       9                 :  * http://www.mozilla.org/MPL/
      10                 :  *
      11                 :  * Software distributed under the License is distributed on an "AS IS" basis,
      12                 :  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
      13                 :  * for the specific language governing rights and limitations under the
      14                 :  * License.
      15                 :  *
      16                 :  * The Original Code is C++ priority queue implementation.
      17                 :  *
      18                 :  * The Initial Developer of the Original Code is Brian Birtles.
      19                 :  * Portions created by the Initial Developer are Copyright (C) 2009
      20                 :  * the Initial Developer. All Rights Reserved.
      21                 :  *
      22                 :  * Contributor(s):
      23                 :  *   Brian Birtles <birtles@gmail.com>
      24                 :  *
      25                 :  * Alternatively, the contents of this file may be used under the terms of
      26                 :  * either of the GNU General Public License Version 2 or later (the "GPL"),
      27                 :  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
      28                 :  * in which case the provisions of the GPL or the LGPL are applicable instead
      29                 :  * of those above. If you wish to allow use of your version of this file only
      30                 :  * under the terms of either the GPL or the LGPL, and not to allow others to
      31                 :  * use your version of this file under the terms of the MPL, indicate your
      32                 :  * decision by deleting the provisions above and replace them with the notice
      33                 :  * and other provisions required by the GPL or the LGPL. If you do not delete
      34                 :  * the provisions above, a recipient may use your version of this file under
      35                 :  * the terms of any one of the MPL, the GPL or the LGPL.
      36                 :  *
      37                 :  * ***** END LICENSE BLOCK ***** */
      38                 : 
      39                 : #ifndef NS_TPRIORITY_QUEUE_H_
      40                 : #define NS_TPRIORITY_QUEUE_H_
      41                 : 
      42                 : #include "nsTArray.h"
      43                 : #include "nsDebug.h"
      44                 : 
      45                 : /**
      46                 :  * A templatized priority queue data structure that uses an nsTArray to serve as
      47                 :  * a binary heap. The default comparator causes this to act like a min-heap.
      48                 :  * Only the LessThan method of the comparator is used.
      49                 :  */
      50                 : template<class T, class Compare = nsDefaultComparator<T, T> >
      51                 : class nsTPriorityQueue
      52               0 : {
      53                 : public:
      54                 :   typedef typename nsTArray<T>::size_type size_type;
      55                 : 
      56                 :   /**
      57                 :    * Default constructor also creates a comparator object using the default
      58                 :    * constructor for type Compare.
      59                 :    */
      60               0 :   nsTPriorityQueue() : mCompare(Compare()) { }
      61                 : 
      62                 :   /**
      63                 :    * Constructor to allow a specific instance of a comparator object to be
      64                 :    * used.
      65                 :    */
      66                 :   nsTPriorityQueue(const Compare& aComp) : mCompare(aComp) { }
      67                 : 
      68                 :   /**
      69                 :    * Copy constructor
      70                 :    */
      71                 :   nsTPriorityQueue(const nsTPriorityQueue& aOther)
      72                 :     : mElements(aOther.mElements),
      73                 :       mCompare(aOther.mCompare)
      74                 :   { }
      75                 : 
      76                 :   /**
      77                 :    * @return True if the queue is empty or false otherwise.
      78                 :    */
      79               0 :   bool IsEmpty() const
      80                 :   {
      81               0 :     return mElements.IsEmpty();
      82                 :   }
      83                 : 
      84                 :   /**
      85                 :    * @return The number of elements in the queue.
      86                 :    */
      87               0 :   size_type Length() const
      88                 :   {
      89               0 :     return mElements.Length();
      90                 :   }
      91                 : 
      92                 :   /**
      93                 :    * @return The topmost element in the queue without changing the queue. This
      94                 :    * is the element 'a' such that there is no other element 'b' in the queue for
      95                 :    * which Compare(b, a) returns true. (Since this container does not check
      96                 :    * for duplicate entries there may exist 'b' for which Compare(a, b) returns
      97                 :    * false.)
      98                 :    */
      99               0 :   const T& Top() const
     100                 :   {
     101               0 :     NS_ABORT_IF_FALSE(!mElements.IsEmpty(), "Empty queue");
     102               0 :     return mElements[0];
     103                 :   }
     104                 : 
     105                 :   /**
     106                 :    * Adds an element to the queue
     107                 :    * @param aElement The element to add
     108                 :    * @return true on success, false on out of memory.
     109                 :    */
     110               0 :   bool Push(const T& aElement)
     111                 :   {
     112               0 :     T* elem = mElements.AppendElement(aElement);
     113               0 :     if (!elem)
     114               0 :       return false; // Out of memory
     115                 : 
     116                 :     // Sift up
     117               0 :     size_type i = mElements.Length() - 1;
     118               0 :     while (i) {
     119               0 :       size_type parent = (size_type)((i - 1) / 2);
     120               0 :       if (mCompare.LessThan(mElements[parent], mElements[i])) {
     121               0 :         break;
     122                 :       }
     123               0 :       Swap(i, parent);
     124               0 :       i = parent;
     125                 :     }
     126                 : 
     127               0 :     return true;
     128                 :   }
     129                 : 
     130                 :   /**
     131                 :    * Removes and returns the top-most element from the queue.
     132                 :    * @return The topmost element, that is, the element 'a' such that there is no
     133                 :    * other element 'b' in the queue for which Compare(b, a) returns true.
     134                 :    * @see Top()
     135                 :    */
     136               0 :   T Pop()
     137                 :   {
     138               0 :     NS_ABORT_IF_FALSE(!mElements.IsEmpty(), "Empty queue");
     139               0 :     T pop = mElements[0];
     140                 : 
     141                 :     // Move last to front
     142               0 :     mElements[0] = mElements[mElements.Length() - 1];
     143               0 :     mElements.TruncateLength(mElements.Length() - 1);
     144                 : 
     145                 :     // Sift down
     146               0 :     size_type i = 0;
     147               0 :     while (2*i + 1 < mElements.Length()) {
     148               0 :       size_type swap = i;
     149               0 :       size_type l_child = 2*i + 1;
     150               0 :       if (mCompare.LessThan(mElements[l_child], mElements[i])) {
     151               0 :         swap = l_child;
     152                 :       }
     153               0 :       size_type r_child = l_child + 1;
     154               0 :       if (r_child < mElements.Length() &&
     155                 :           mCompare.LessThan(mElements[r_child], mElements[swap])) {
     156               0 :         swap = r_child;
     157                 :       }
     158               0 :       if (swap == i) {
     159               0 :         break;
     160                 :       }
     161               0 :       Swap(i, swap);
     162               0 :       i = swap;
     163                 :     }
     164                 : 
     165                 :     return pop;
     166                 :   }
     167                 : 
     168                 :   /**
     169                 :    * Removes all elements from the queue.
     170                 :    */
     171               0 :   void Clear()
     172                 :   {
     173               0 :     mElements.Clear();
     174               0 :   }
     175                 : 
     176                 :   /**
     177                 :    * Provides readonly access to the queue elements as an array. Generally this
     178                 :    * should be avoided but may be needed in some situations such as when the
     179                 :    * elements contained in the queue need to be enumerated for cycle-collection.
     180                 :    * @return A pointer to the first element of the array.  If the array is
     181                 :    * empty, then this pointer must not be dereferenced.
     182                 :    */
     183               0 :   const T* Elements() const
     184                 :   {
     185               0 :     return mElements.Elements();
     186                 :   }
     187                 : 
     188                 : protected:
     189                 :   /**
     190                 :    * Swaps the elements at the specified indices.
     191                 :    */
     192               0 :   void Swap(size_type aIndexA, size_type aIndexB)
     193                 :   {
     194               0 :     T temp = mElements[aIndexA];
     195               0 :     mElements[aIndexA] = mElements[aIndexB];
     196               0 :     mElements[aIndexB] = temp;
     197               0 :   }
     198                 : 
     199                 :   nsTArray<T> mElements;
     200                 :   Compare mCompare; // Comparator object
     201                 : };
     202                 : 
     203                 : #endif // NS_TPRIORITY_QUEUE_H_

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