68 lines
1.9 KiB
C++
68 lines
1.9 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_TAG_FALLBACK_HXX
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#define MPD_TAG_FALLBACK_HXX
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#include <utility>
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/**
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* Invoke the given function for all fallback tags of the given
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* #TagType, until the function returns true (or until there are no
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* more fallback tags).
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*/
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template<typename F>
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bool
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ApplyTagFallback(TagType type, F &&f) noexcept
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{
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if (type == TAG_ALBUM_ARTIST_SORT) {
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/* fall back to "AlbumArtist", "ArtistSort" and
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"Artist" if no "AlbumArtistSort" was found */
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if (f(TAG_ALBUM_ARTIST))
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return true;
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return ApplyTagFallback(TAG_ARTIST_SORT, std::forward<F>(f));
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}
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if (type == TAG_ALBUM_ARTIST || type == TAG_ARTIST_SORT)
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/* fall back to "Artist" if no
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"AlbumArtist"/"ArtistSort" was found */
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return f(TAG_ARTIST);
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if (type == TAG_ALBUM_SORT)
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/* fall back to "Album" if no "AlbumSort" was found */
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return f(TAG_ALBUM);
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return false;
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}
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/**
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* Invoke the given function for the given #TagType and all of its
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* fallback tags, until the function returns true (or until there are
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* no more fallback tags).
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*/
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template<typename F>
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bool
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ApplyTagWithFallback(TagType type, F &&f) noexcept
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{
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return f(type) || ApplyTagFallback(type, std::forward<F>(f));
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}
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#endif
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