db/Helpers: move TagSet to dedicated header

Makefile.am

@@ -714,6 +714,7 @@ libtag_a_SOURCES =\
 	src/tag/TagString.cxx src/tag/TagString.hxx \
 	src/tag/TagPool.cxx src/tag/TagPool.hxx \
 	src/tag/TagTable.cxx src/tag/TagTable.hxx \
+	src/tag/Set.hxx \
 	src/tag/ApeLoader.cxx src/tag/ApeLoader.hxx \
 	src/tag/ApeReplayGain.cxx src/tag/ApeReplayGain.hxx \
 	src/tag/ApeTag.cxx src/tag/ApeTag.hxx

src/db/Helpers.cxx

@@ -23,6 +23,7 @@
 #include "LightSong.hxx"
 #include "tag/Tag.hxx"
 #include "tag/TagBuilder.hxx"
+#include "tag/Set.hxx"
 
 #include <functional>
 #include <set>
@@ -39,30 +40,6 @@ struct StringLess {
 
 typedef std::set<const char *, StringLess> StringSet;
 
-struct TagLess {
-	gcc_pure
-	bool operator()(const Tag &a, const Tag &b) const {
-		if (a.num_items != b.num_items)
-			return a.num_items < b.num_items;
-
-		const unsigned n = a.num_items;
-		for (unsigned i = 0; i < n; ++i) {
-			const TagItem &ai = *a.items[i];
-			const TagItem &bi = *b.items[i];
-			if (ai.type != bi.type)
-				return unsigned(ai.type) < unsigned(bi.type);
-
-			const int cmp = strcmp(ai.value, bi.value);
-			if (cmp != 0)
-				return cmp < 0;
-		}
-
-		return false;
-	}
-};
-
-typedef std::set<Tag, TagLess> TagSet;
-
 /**
  * Copy all tag items of the specified type.
  */

src/tag/Set.hxx

@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2003-2014 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_SET_HXX
+#define MPD_TAG_SET_HXX
+
+#include "Compiler.h"
+#include "Tag.hxx"
+
+#include <set>
+
+#include <string.h>
+
+/**
+ * Helper class for #TagSet which compares two #Tag objects.
+ */
+struct TagLess {
+	gcc_pure
+	bool operator()(const Tag &a, const Tag &b) const {
+		if (a.num_items != b.num_items)
+			return a.num_items < b.num_items;
+
+		const unsigned n = a.num_items;
+		for (unsigned i = 0; i < n; ++i) {
+			const TagItem &ai = *a.items[i];
+			const TagItem &bi = *b.items[i];
+			if (ai.type != bi.type)
+				return unsigned(ai.type) < unsigned(bi.type);
+
+			const int cmp = strcmp(ai.value, bi.value);
+			if (cmp != 0)
+				return cmp < 0;
+		}
+
+		return false;
+	}
+};
+
+/**
+ * A set of #Tag objects.
+ */
+typedef std::set<Tag, TagLess> TagSet;
+
+#endif