randomlistmodel.cpp Example File

tools/contiguouscache/randomlistmodel.cpp
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#include "randomlistmodel.h" #include <stdlib.h> static const int bufferSize(500); static const int lookAhead(100); static const int halfLookAhead(lookAhead/2); RandomListModel::RandomListModel(QObject *parent) : QAbstractListModel(parent), m_rows(bufferSize), m_count(10000) { } RandomListModel::~RandomListModel() { } int RandomListModel::rowCount(const QModelIndex &) const { return m_count; } QVariant RandomListModel::data(const QModelIndex &index, int role) const { if (role != Qt::DisplayRole) return QVariant(); int row = index.row(); if (row > m_rows.lastIndex()) { if (row - m_rows.lastIndex() > lookAhead) cacheRows(row-halfLookAhead, qMin(m_count, row+halfLookAhead)); else while (row > m_rows.lastIndex()) m_rows.append(fetchRow(m_rows.lastIndex()+1)); } else if (row < m_rows.firstIndex()) { if (m_rows.firstIndex() - row > lookAhead) cacheRows(qMax(0, row-halfLookAhead), row+halfLookAhead); else while (row < m_rows.firstIndex()) m_rows.prepend(fetchRow(m_rows.firstIndex()-1)); } return m_rows.at(row); } void RandomListModel::cacheRows(int from, int to) const { for (int i = from; i <= to; ++i) m_rows.insert(i, fetchRow(i)); } QString RandomListModel::fetchRow(int position) const { return QString::number(rand() % ++position); }