Fix serialization bug for TagSet

fdbclient/TagThrottle.h

@@ -66,15 +66,15 @@ struct dynamic_size_traits<TagSet> : std::true_type {
 	// May be called multiple times during one serialization
 	template <class Context>
 	static size_t size(const TagSet& t, Context&) {
-		return t.tags.size() + t.bytes;
+		return 1 + t.tags.size() + t.bytes;
 	}
 
 	// Guaranteed to be called only once during serialization
 	template <class Context>
 	static void save(uint8_t* out, const TagSet& t, Context&) {
+		*(out++) = (uint8_t)t.size();
 		for (const auto& tag : t.tags) {
-			*out = (uint8_t)tag.size();
-			++out;
+			*(out++) = (uint8_t)tag.size();
 
 			std::copy(tag.begin(), tag.end(), out);
 			out += tag.size();
@@ -85,10 +85,11 @@ struct dynamic_size_traits<TagSet> : std::true_type {
 	// load call tree.
 	template <class Context>
 	static void load(const uint8_t* data, size_t size, TagSet& t, Context& context) {
+		const uint8_t *start = data;
 		const uint8_t *end = data + size;
-		while(data < end) {
-			uint8_t len = *data;
-			++data;
+		uint8_t count = *(data++);
+		for(uint8_t i = 0; i < count; ++i) {
+			uint8_t len = *(data++);
 			TransactionTagRef tag(context.tryReadZeroCopy(data, len), len);
 			data += len;
 
@@ -96,6 +97,8 @@ struct dynamic_size_traits<TagSet> : std::true_type {
 			t.bytes += tag.size();
 		}
 
+		ASSERT(data <= end);
+
 		// Deserialized tag sets share the arena with the request that contained them
 		// For this reason, persisting a TagSet that shares memory with other request
 		// members should be done with caution.