3 files changed, 29 insertions, 40 deletions
diff --git a/src/tag/Tag.cxx b/src/tag/Tag.cxx
index 0fb7ea93b..7d1da63df 100644
--- a/src/tag/Tag.cxx
+++ b/src/tag/Tag.cxx
@@ -22,6 +22,7 @@
 #include "TagPool.hxx"
 #include "TagString.hxx"
 #include "TagSettings.h"
+#include "TagBuilder.hxx"
 #include "util/ASCII.hxx"
 
 #include <glib.h>
@@ -108,46 +109,9 @@ Tag::Tag(const Tag &other)
 Tag *
 Tag::Merge(const Tag &base, const Tag &add)
 {
-	unsigned n;
-
-	/* allocate new tag object */
-
-	Tag *ret = new Tag();
-	ret->time = add.time > 0 ? add.time : base.time;
-	ret->num_items = base.num_items + add.num_items;
-	ret->items = ret->num_items > 0
-		? (TagItem **)g_malloc(items_size(*ret))
-		: nullptr;
-
-	tag_pool_lock.lock();
-
-	/* copy all items from "add" */
-
-	for (unsigned i = 0; i < add.num_items; ++i)
-		ret->items[i] = tag_pool_dup_item(add.items[i]);
-
-	n = add.num_items;
-
-	/* copy additional items from "base" */
-
-	for (unsigned i = 0; i < base.num_items; ++i)
-		if (!add.HasType(base.items[i]->type))
-			ret->items[n++] = tag_pool_dup_item(base.items[i]);
-
-	tag_pool_lock.unlock();
-
-	assert(n <= ret->num_items);
-
-	if (n < ret->num_items) {
-		/* some tags were not copied - shrink ret->items */
-		assert(n > 0);
-
-		ret->num_items = n;
-		ret->items = (TagItem **)
-			g_realloc(ret->items, items_size(*ret));
-	}
-
-	return ret;
+	TagBuilder builder(base);
+	builder.Complement(add);
+	return builder.Commit();
 }
 
 Tag *
diff --git a/src/tag/TagBuilder.cxx b/src/tag/TagBuilder.cxx
index 15e32bb01..6ba8c12db 100644
--- a/src/tag/TagBuilder.cxx
+++ b/src/tag/TagBuilder.cxx
@@ -109,6 +109,25 @@ TagBuilder::HasType(TagType type) const
 	return false;
 }
 
+void
+TagBuilder::Complement(const Tag &other)
+{
+	if (time <= 0)
+		time = other.time;
+
+	has_playlist |= other.has_playlist;
+
+	items.reserve(items.size() + other.num_items);
+
+	tag_pool_lock.lock();
+	for (unsigned i = 0, n = other.num_items; i != n; ++i) {
+		TagItem *item = other.items[i];
+		if (!HasType(item->type))
+			items.push_back(tag_pool_dup_item(item));
+	}
+	tag_pool_lock.unlock();
+}
+
 inline void
 TagBuilder::AddItemInternal(TagType type, const char *value, size_t length)
 {
diff --git a/src/tag/TagBuilder.hxx b/src/tag/TagBuilder.hxx
index 5804a7940..52ccf466c 100644
--- a/src/tag/TagBuilder.hxx
+++ b/src/tag/TagBuilder.hxx
@@ -119,6 +119,12 @@ public:
 	bool HasType(TagType type) const;
 
 	/**
+	 * Copy attributes and items from the other object that do not
+	 * exist in this object.
+	 */
+	void Complement(const Tag &other);
+
+	/**
 	 * Appends a new tag item.
 	 *
 	 * @param type the type of the new tag item