xpcom/glue/nsTPriorityQueue.h@129ffea94266
xpcom/glue/nsTPriorityQueue.h
Sat, 03 Jan 2015 20:18:00 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Sat, 03 Jan 2015 20:18:00 +0100
- branch
- TOR_BUG_3246
- changeset 7
- 129ffea94266
- permissions
- -rw-r--r--
Conditionally enable double key logic according to:
private browsing mode or privacy.thirdparty.isolate preference and
implement in GetCookieStringCommon and FindCookie where it counts...
With some reservations of how to convince FindCookie users to test
condition and pass a nullptr when disabling double key logic.
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 /* This Source Code Form is subject to the terms of the Mozilla Public
4 * License, v. 2.0. If a copy of the MPL was not distributed with this
5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
7 #ifndef NS_TPRIORITY_QUEUE_H_
8 #define NS_TPRIORITY_QUEUE_H_
10 #include "nsTArray.h"
11 #include "nsDebug.h"
13 /**
14 * A templatized priority queue data structure that uses an nsTArray to serve as
15 * a binary heap. The default comparator causes this to act like a min-heap.
16 * Only the LessThan method of the comparator is used.
17 */
18 template<class T, class Compare = nsDefaultComparator<T, T> >
19 class nsTPriorityQueue
20 {
21 public:
22 typedef typename nsTArray<T>::size_type size_type;
24 /**
25 * Default constructor also creates a comparator object using the default
26 * constructor for type Compare.
27 */
28 nsTPriorityQueue() : mCompare(Compare()) { }
30 /**
31 * Constructor to allow a specific instance of a comparator object to be
32 * used.
33 */
34 nsTPriorityQueue(const Compare& aComp) : mCompare(aComp) { }
36 /**
37 * Copy constructor
38 */
39 nsTPriorityQueue(const nsTPriorityQueue& aOther)
40 : mElements(aOther.mElements),
41 mCompare(aOther.mCompare)
42 { }
44 /**
45 * @return True if the queue is empty or false otherwise.
46 */
47 bool IsEmpty() const
48 {
49 return mElements.IsEmpty();
50 }
52 /**
53 * @return The number of elements in the queue.
54 */
55 size_type Length() const
56 {
57 return mElements.Length();
58 }
60 /**
61 * @return The topmost element in the queue without changing the queue. This
62 * is the element 'a' such that there is no other element 'b' in the queue for
63 * which Compare(b, a) returns true. (Since this container does not check
64 * for duplicate entries there may exist 'b' for which Compare(a, b) returns
65 * false.)
66 */
67 const T& Top() const
68 {
69 NS_ABORT_IF_FALSE(!mElements.IsEmpty(), "Empty queue");
70 return mElements[0];
71 }
73 /**
74 * Adds an element to the queue
75 * @param aElement The element to add
76 * @return true on success, false on out of memory.
77 */
78 bool Push(const T& aElement)
79 {
80 T* elem = mElements.AppendElement(aElement);
81 if (!elem)
82 return false; // Out of memory
84 // Sift up
85 size_type i = mElements.Length() - 1;
86 while (i) {
87 size_type parent = (size_type)((i - 1) / 2);
88 if (mCompare.LessThan(mElements[parent], mElements[i])) {
89 break;
90 }
91 Swap(i, parent);
92 i = parent;
93 }
95 return true;
96 }
98 /**
99 * Removes and returns the top-most element from the queue.
100 * @return The topmost element, that is, the element 'a' such that there is no
101 * other element 'b' in the queue for which Compare(b, a) returns true.
102 * @see Top()
103 */
104 T Pop()
105 {
106 NS_ABORT_IF_FALSE(!mElements.IsEmpty(), "Empty queue");
107 T pop = mElements[0];
109 // Move last to front
110 mElements[0] = mElements[mElements.Length() - 1];
111 mElements.TruncateLength(mElements.Length() - 1);
113 // Sift down
114 size_type i = 0;
115 while (2*i + 1 < mElements.Length()) {
116 size_type swap = i;
117 size_type l_child = 2*i + 1;
118 if (mCompare.LessThan(mElements[l_child], mElements[i])) {
119 swap = l_child;
120 }
121 size_type r_child = l_child + 1;
122 if (r_child < mElements.Length() &&
123 mCompare.LessThan(mElements[r_child], mElements[swap])) {
124 swap = r_child;
125 }
126 if (swap == i) {
127 break;
128 }
129 Swap(i, swap);
130 i = swap;
131 }
133 return pop;
134 }
136 /**
137 * Removes all elements from the queue.
138 */
139 void Clear()
140 {
141 mElements.Clear();
142 }
144 /**
145 * Provides readonly access to the queue elements as an array. Generally this
146 * should be avoided but may be needed in some situations such as when the
147 * elements contained in the queue need to be enumerated for cycle-collection.
148 * @return A pointer to the first element of the array. If the array is
149 * empty, then this pointer must not be dereferenced.
150 */
151 const T* Elements() const
152 {
153 return mElements.Elements();
154 }
156 protected:
157 /**
158 * Swaps the elements at the specified indices.
159 */
160 void Swap(size_type aIndexA, size_type aIndexB)
161 {
162 T temp = mElements[aIndexA];
163 mElements[aIndexA] = mElements[aIndexB];
164 mElements[aIndexB] = temp;
165 }
167 nsTArray<T> mElements;
168 Compare mCompare; // Comparator object
169 };
171 #endif // NS_TPRIORITY_QUEUE_H_
