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https://github.com/qbittorrent/qBittorrent.git
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1a913c502b
Explicit or implicit calls to begin() and end() cause a non-const
container to detach from shared data, ie. to perform a deep-copy to gain
a unique copy of the data.
That can be a expensive although unneeded operation.
In order to assist the developer a copyAsConst function is added.
copyAsConst returns a const copy of the object.
For lvalues just use qAsConst. It's only available on Qt 5.7.0. But we
added also for earlier versions. The developer can always use qAsConst.
Intended uses:
QString s = ...;
for (const auto &ch : qAsConst(s))
process(ch);
for (const auto &ch : copyAsConst(funcReturningQString()))
process(ch);
48 lines
1.9 KiB
C++
48 lines
1.9 KiB
C++
/*
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* Bittorrent Client using Qt and libtorrent.
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* Copyright (C) 2016 Mike Tzou
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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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#pragma once
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#include <type_traits>
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#include <QtGlobal>
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const char C_TORRENT_FILE_EXTENSION[] = ".torrent";
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#if QT_VERSION < QT_VERSION_CHECK(5, 7, 0)
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template <typename T>
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constexpr typename std::add_const<T>::type &qAsConst(T &t) noexcept { return t; }
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// prevent rvalue arguments:
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template <typename T>
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void qAsConst(const T &&) = delete;
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#endif
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// returns a const object copy
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template <typename T>
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constexpr typename std::add_const<T>::type copyAsConst(T &&t) noexcept { return std::move(t); }
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