LCOV - app.info - objdir/dist/include/nsTPriorityQueue.h

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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