TagBuilder: allow adding duplicate tag types in Complement()

Build a table of pre-existing tag types before adding new items.  The
old way would check HasType() each time, which would return true after
the first instance of that tag type had been added, preventing
duplicate tag types to be merged.

This broke duplicate tag types loaded from the state file, because
this code path uses TagBuilder::Complement().

2 files changed, 11 insertions, 1 deletions

diff --git a/NEWS b/NEWS
index da153cfa1..22920348b 100644
--- a/NEWS
+++ b/NEWS
@@ -1,6 +1,7 @@
 ver 0.19.9 (not yet released)
 * decoder
   - dsdiff, dsf: raise ID3 tag limit to 1 MB
+* playlist: fix loading duplicate tag types from state file
 * fix clock integer overflow on OS X
 * fix build failure with uClibc
 * fix build failure on non-POSIX operating systems
diff --git a/src/tag/TagBuilder.cxx b/src/tag/TagBuilder.cxx
index 93518f6e9..0882f9561 100644
--- a/src/tag/TagBuilder.cxx
+++ b/src/tag/TagBuilder.cxx
@@ -25,6 +25,8 @@
 #include "Tag.hxx"
 #include "util/WritableBuffer.hxx"
 
+#include <array>
+
 #include <assert.h>
 #include <string.h>
 #include <stdlib.h>
@@ -168,12 +170,19 @@ TagBuilder::Complement(const Tag &other)
 
 	has_playlist |= other.has_playlist;
 
+	/* build a table of tag types that were already present in
+	   this object, which will not be copied from #other */
+	std::array<bool, TAG_NUM_OF_ITEM_TYPES> present;
+	present.fill(false);
+	for (const TagItem *i : items)
+		present[i->type] = true;
+
 	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))
+		if (!present[item->type])
 			items.push_back(tag_pool_dup_item(item));
 	}
 	tag_pool_lock.unlock();