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/*
* Copyright 2003-2021 The Music Player Daemon Project
* http://www.musicpd.org
*
* This program 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 2 of the License, or
* (at your option) any later version.
*
* This program 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 this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifndef MPD_DB_SIMPLE_EXPORTED_SONG_HXX
#define MPD_DB_SIMPLE_EXPORTED_SONG_HXX
#include "song/LightSong.hxx"
#include "tag/Tag.hxx"
/**
* The return type for Song::Export(). In addition to implementing
* #LightSong, it hold allocations necessary to represent the #Song as
* a #LightSong, e.g. a merged #Tag.
*/
class ExportedSong : public LightSong {
/**
* A reference target for LightSong::tag, but it is only used
* if this instance "owns" the #Tag. For instances referring
* to a foreign #Tag instance (e.g. a Song::tag), this field
* is not used (and empty).
*/
Tag tag_buffer;
public:
using LightSong::LightSong;
ExportedSong(const char *_uri, Tag &&_tag) noexcept
:LightSong(_uri, tag_buffer),
tag_buffer(std::move(_tag)) {}
/* this custom move constructor is necessary so LightSong::tag
points to this instance's #Tag field instead of leaving a
dangling reference to the source object's #Tag field */
ExportedSong(ExportedSong &&src) noexcept
:LightSong(src,
/* refer to tag_buffer only if the
moved-from instance also owned the Tag
which its LightSong::tag field refers
to */
OwnsTag() ? tag_buffer : src.tag),
tag_buffer(std::move(src.tag_buffer)) {}
ExportedSong &operator=(ExportedSong &&) = delete;
private:
bool OwnsTag() const noexcept {
return &tag == &tag_buffer;
}
};
#endif
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