db/VHelper: move CompareTags() to tag/Sort.cxx

src/tag/Sort.cxx

@@ -0,0 +1,57 @@
+/*
+ * 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.
+ */
+
+#include "Sort.hxx"
+#include "Tag.hxx"
+
+#include <algorithm>
+
+#include <string.h>
+#include <stdlib.h>
+
+[[gnu::pure]]
+static bool
+CompareNumeric(const char *a, const char *b) noexcept
+{
+	long a_value = strtol(a, nullptr, 10);
+	long b_value = strtol(b, nullptr, 10);
+
+	return a_value < b_value;
+}
+
+bool
+CompareTags(TagType type, bool descending, const Tag &a, const Tag &b) noexcept
+{
+	const char *a_value = a.GetSortValue(type);
+	const char *b_value = b.GetSortValue(type);
+
+	if (descending) {
+		using std::swap;
+		swap(a_value, b_value);
+	}
+
+	switch (type) {
+	case TAG_DISC:
+	case TAG_TRACK:
+		return CompareNumeric(a_value, b_value);
+
+	default:
+		return strcmp(a_value, b_value) < 0;
+	}
+}

src/tag/Sort.hxx

@@ -0,0 +1,29 @@
+/*
+ * 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.
+ */
+
+#pragma once
+
+#include "Type.h"
+
+struct Tag;
+
+[[gnu::pure]]
+bool
+CompareTags(TagType type, bool descending,
+	    const Tag &a, const Tag &b) noexcept;

src/tag/meson.build

@@ -18,6 +18,7 @@ tag_sources = [
   'Builder.cxx',
   'Handler.cxx',
   'Settings.cxx',
+  'Sort.cxx',
   'Config.cxx',
   'ParseName.cxx',
   parse_name_cxx,