Qt 4.8
qtconcurrentmedian.h
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41 
42 #ifndef QTCONCURRENT_MEDIAN_H
43 #define QTCONCURRENT_MEDIAN_H
44 
45 #include <QtCore/qglobal.h>
46 
47 #ifndef QT_NO_CONCURRENT
48 
49 #include <QtCore/qvector.h>
50 #include <QtCore/qalgorithms.h>
51 
54 
55 QT_MODULE(Core)
56 
57 #ifndef qdoc
58 
59 namespace QtConcurrent {
60 
61 template <typename T>
62 class Median
63 {
64 public:
65  Median(int _bufferSize)
66  : currentMedian(), bufferSize(_bufferSize), currentIndex(0), valid(false), dirty(true)
67  {
68  values.resize(bufferSize);
69  }
70 
71  void reset()
72  {
73  values.fill(0);
74  currentIndex = 0;
75  valid = false;
76  dirty = true;
77  }
78 
79  void addValue(T value)
80  {
81  currentIndex = ((currentIndex + 1) % bufferSize);
82  if (valid == false && currentIndex % bufferSize == 0)
83  valid = true;
84 
85  // Only update the cached median value when we have to, that
86  // is when the new value is on then other side of the median
87  // compared to the current value at the index.
88  const T currentIndexValue = values[currentIndex];
89  if ((currentIndexValue > currentMedian && currentMedian > value)
90  || (currentMedian > currentIndexValue && value > currentMedian)) {
91  dirty = true;
92  }
93 
94  values[currentIndex] = value;
95  }
96 
97  bool isMedianValid() const
98  {
99  return valid;
100  }
101 
102  T median()
103  {
104  if (dirty) {
105  dirty = false;
106  QVector<T> sorted = values;
107  qSort(sorted);
108  currentMedian = sorted.at(bufferSize / 2 + 1);
109  }
110  return currentMedian;
111  }
112 private:
114  T currentMedian;
115  int bufferSize;
116  int currentIndex;
117  bool valid;
118  bool dirty;
119 };
120 
121 } // namespace QtConcurrent
122 
123 #endif //qdoc
124 
127 
128 #endif // QT_NO_CONCURRENT
129 
130 #endif
#define QT_END_NAMESPACE
This macro expands to.
Definition: qglobal.h:90
#define QT_MODULE(x)
Definition: qglobal.h:2783
#define QT_BEGIN_HEADER
Definition: qglobal.h:136
Q_CORE_EXPORT QTextStream & reset(QTextStream &s)
The QVector class is a template class that provides a dynamic array.
Definition: qdatastream.h:64
#define QT_BEGIN_NAMESPACE
This macro expands to.
Definition: qglobal.h:89
quint16 values[128]
void qSort(RandomAccessIterator start, RandomAccessIterator end)
Definition: qalgorithms.h:177
const T & at(int i) const
Returns the item at index position i in the vector.
Definition: qvector.h:350
The QtConcurrent namespace provides high-level APIs that make it possible to write multi-threaded pro...
#define QT_END_HEADER
Definition: qglobal.h:137