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