Clementine-audio-player-Mac.../src/core/cachedlist.h

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/* This file is part of Clementine.
Copyright 2011, David Sansome <me@davidsansome.com>
Clementine is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Clementine is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with Clementine. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef CACHEDLIST_H
#define CACHEDLIST_H
#include <QDateTime>
#include <QSettings>
template <typename T>
class CachedList {
public:
// Use a CachedList when you want to download and save a list of things from a
// remote service, updating it only periodically.
// T must be a registered metatype and must support being stored in
// QSettings. This usually means you have to implement QDataStream streaming
// operators, and use qRegisterMetaTypeStreamOperators.
typedef QList<T> ListType;
CachedList(const char* settings_group, const QString& name,
int cache_duration_secs)
: settings_group_(settings_group),
name_(name),
cache_duration_secs_(cache_duration_secs) {
}
void Load() {
QSettings s;
s.beginGroup(settings_group_);
last_updated_ = s.value("last_refreshed_" + name_).toDateTime();
data_.clear();
const int count = s.beginReadArray(name_ + "_data");
for (int i=0 ; i<count ; ++i) {
s.setArrayIndex(i);
data_ << s.value("value").value<T>();
}
s.endArray();
}
void Save() const {
QSettings s;
s.beginGroup(settings_group_);
s.setValue("last_refreshed_" + name_, last_updated_);
s.beginWriteArray(name_ + "_data", data_.size());
for (int i=0 ; i<data_.size() ; ++i) {
s.setArrayIndex(i);
s.setValue("value", QVariant::fromValue(data_[i]));
}
s.endArray();
}
void Update(const ListType& data) {
data_ = data;
last_updated_ = QDateTime::currentDateTime();
Save();
}
bool IsStale() const {
return last_updated_.isNull() ||
last_updated_.secsTo(QDateTime::currentDateTime()) > cache_duration_secs_;
}
const ListType& Data() const { return data_; }
operator ListType() const { return data_; }
// Q_FOREACH support
typedef typename ListType::const_iterator const_iterator;
const_iterator begin() const { return data_.begin(); }
const_iterator end() const { return data_.end(); }
private:
const char* settings_group_;
const QString name_;
const int cache_duration_secs_;
QDateTime last_updated_;
ListType data_;
};
#endif // CACHEDLIST_H