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https://github.com/qbittorrent/qBittorrent.git
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c75500670d
So instead of passing every function objects by value (a copy is made), now function objects will be handled properly by reference (for lvalues) or by value (for rvalues).
115 lines
3.9 KiB
C++
115 lines
3.9 KiB
C++
/*
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* Bittorrent Client using Qt and libtorrent.
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* Copyright (C) 2016 Vladimir Golovnev <glassez@yandex.ru>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* In addition, as a special exception, the copyright holders give permission to
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* link this program with the OpenSSL project's "OpenSSL" library (or with
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* modified versions of it that use the same license as the "OpenSSL" library),
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* and distribute the linked executables. You must obey the GNU General Public
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* License in all respects for all of the code used other than "OpenSSL". If you
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* modify file(s), you may extend this exception to your version of the file(s),
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* but you are not obligated to do so. If you do not wish to do so, delete this
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* exception statement from your version.
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*/
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#ifndef SETTINGVALUE_H
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#define SETTINGVALUE_H
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#include <type_traits>
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#include <QMetaEnum>
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#include <QString>
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#include "settingsstorage.h"
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template <typename T>
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class CachedSettingValue
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{
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public:
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explicit CachedSettingValue(const char *keyName, const T &defaultValue = T())
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: m_keyName(QLatin1String(keyName))
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, m_value(loadValue(defaultValue))
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{
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}
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// The signature of the ProxyFunc should be equivalent to the following:
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// T proxyFunc(const T &a);
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template <typename ProxyFunc>
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explicit CachedSettingValue(const char *keyName, const T &defaultValue
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, ProxyFunc &&proxyFunc)
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: m_keyName(QLatin1String(keyName))
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, m_value(proxyFunc(loadValue(defaultValue)))
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{
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}
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T value() const
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{
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return m_value;
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}
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operator T() const
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{
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return value();
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}
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CachedSettingValue<T> &operator=(const T &newValue)
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{
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m_value = newValue;
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storeValue(m_value);
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return *this;
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}
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private:
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// regular load/save pair
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template <typename U, typename std::enable_if<!std::is_enum<U>::value, int>::type = 0>
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U loadValue(const U &defaultValue)
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{
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return SettingsStorage::instance()->loadValue(m_keyName, defaultValue).template value<T>();
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}
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template <typename U, typename std::enable_if<!std::is_enum<U>::value, int>::type = 0>
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void storeValue(const U &value)
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{
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SettingsStorage::instance()->storeValue(m_keyName, value);
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}
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// load/save pair for an enum
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// saves literal value of the enum constant, obtained from QMetaEnum
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template <typename U, typename std::enable_if<std::is_enum<U>::value, int>::type = 0>
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U loadValue(const U &defaultValue)
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{
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static_assert(std::is_same<int, typename std::underlying_type<U>::type>::value,
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"Enumeration underlying type has to be int");
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bool ok = false;
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const U res = static_cast<U>(QMetaEnum::fromType<U>().keyToValue(
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SettingsStorage::instance()->loadValue(m_keyName).toString().toLatin1().constData(), &ok));
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return ok ? res : defaultValue;
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}
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template <typename U, typename std::enable_if<std::is_enum<U>::value, int>::type = 0>
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void storeValue(const U &value)
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{
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SettingsStorage::instance()->storeValue(m_keyName,
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QString::fromLatin1(QMetaEnum::fromType<U>().valueToKey(static_cast<int>(value))));
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}
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const QString m_keyName;
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T m_value;
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};
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#endif // SETTINGVALUE_H
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