db/Count: move code to tag/VisitCallback.hxx

Makefile.am

@@ -978,6 +978,7 @@ libtag_a_SOURCES =\
 	src/tag/TagHandler.cxx src/tag/TagHandler.hxx \
 	src/tag/Mask.hxx \
 	src/tag/Fallback.hxx \
+	src/tag/VisitFallback.hxx \
 	src/tag/Settings.cxx src/tag/Settings.hxx \
 	src/tag/TagConfig.cxx src/tag/TagConfig.hxx \
 	src/tag/TagNames.c \

src/db/Count.cxx

@@ -25,7 +25,7 @@
 #include "client/Response.hxx"
 #include "LightSong.hxx"
 #include "tag/Tag.hxx"
-#include "tag/Fallback.hxx"
+#include "tag/VisitFallback.hxx"
 
 #include <functional>
 #include <map>
@@ -73,24 +73,15 @@ stats_visitor_song(SearchStats &stats, const LightSong &song)
 		stats.total_duration += duration;
 }
 
-static bool
-CollectGroupCounts(TagCountMap &map, TagType group, const Tag &tag)
+static void
+CollectGroupCounts(TagCountMap &map, const Tag &tag,
+		   const char *value) noexcept
 {
-	bool found = false;
-	for (const auto &item : tag) {
-		if (item.type == group) {
-			auto r = map.insert(std::make_pair(item.value,
-							   SearchStats()));
-			SearchStats &s = r.first->second;
-			++s.n_songs;
-			if (!tag.duration.IsNegative())
-				s.total_duration += tag.duration;
-
-			found = true;
-		}
-	}
-
-	return found;
+	auto r = map.insert(std::make_pair(value, SearchStats()));
+	SearchStats &s = r.first->second;
+	++s.n_songs;
+	if (!tag.duration.IsNegative())
+		s.total_duration += tag.duration;
 }
 
 static void
@@ -99,9 +90,10 @@ GroupCountVisitor(TagCountMap &map, TagType group, const LightSong &song)
 	assert(song.tag != nullptr);
 
 	const Tag &tag = *song.tag;
-	ApplyTagWithFallback(group,
+	VisitTagWithFallback(tag, group,
 			     std::bind(CollectGroupCounts, std::ref(map),
-				       std::placeholders::_1, std::cref(tag)));
+				       std::cref(tag),
+				       std::placeholders::_1));
 }
 
 void

src/tag/VisitFallback.hxx

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2003-2018 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_TAG_VISIT_FALLBACK_HXX
+#define MPD_TAG_VISIT_FALLBACK_HXX
+
+#include "Fallback.hxx"
+#include "Tag.hxx"
+
+template<typename F>
+bool
+VisitTagType(const Tag &tag, TagType type, F &&f) noexcept
+{
+	bool found = false;
+
+	for (const auto &item : tag) {
+		if (item.type == type) {
+			found = true;
+			f(item.value);
+		}
+	}
+
+	return found;
+}
+
+template<typename F>
+bool
+VisitTagWithFallback(const Tag &tag, TagType type, F &&f) noexcept
+{
+	return ApplyTagWithFallback(type,
+				    [&](TagType type2) {
+					    return VisitTagType(tag, type2, f);
+				    });
+}
+
+#endif