playlist/xspf: concatenate multiple CharacterData fragments

Closes https://github.com/MusicPlayerDaemon/MPD/issues/781

NEWS

@@ -1,6 +1,8 @@
 ver 0.21.21 (not yet released)
 * configuration
   - fix bug in "metadata_to_use" setting
+* playlist
+  - xspf: fix corrupt tags in the presence of XML entities
 * archive
   - iso9660: skip empty file names to work around libcdio bug
 * decoder

src/playlist/plugins/XspfPlaylistPlugin.cxx

@@ -61,6 +61,8 @@ struct XspfParser {
 	std::string location;
 
 	TagBuilder tag_builder;
+
+	std::string value;
 };
 
 static constexpr struct tag_table xspf_tag_elements[] = {
@@ -81,6 +83,7 @@ xspf_start_element(void *user_data, const XML_Char *element_name,
 		   gcc_unused const XML_Char **atts)
 {
 	XspfParser *parser = (XspfParser *)user_data;
+	parser->value.clear();
 
 	switch (parser->state) {
 	case XspfParser::ROOT:
@@ -154,10 +157,21 @@ xspf_end_element(void *user_data, const XML_Char *element_name)
 		break;
 
 	case XspfParser::TAG:
+		if (!parser->value.empty())
+			parser->tag_builder.AddItem(parser->tag_type,
+						    StringView(parser->value.data(),
+							       parser->value.length()));
+
+		parser->state = XspfParser::TRACK;
+		break;
+
 	case XspfParser::LOCATION:
+		parser->location = std::move(parser->value);
 		parser->state = XspfParser::TRACK;
 		break;
 	}
+
+	parser->value.clear();
 }
 
 static void XMLCALL
@@ -173,13 +187,8 @@ xspf_char_data(void *user_data, const XML_Char *s, int len)
 		break;
 
 	case XspfParser::TAG:
-		parser->tag_builder.AddItem(parser->tag_type,
-					    StringView(s, len));
-		break;
-
 	case XspfParser::LOCATION:
-		parser->location.assign(s, len);
+		parser->value.append(s, len);
-
 		break;
 	}
 }