[btree_damage_visitor] Check the value_size agrees.

Patch from Ming-Hung Tsai

persistent-data/data-structures/btree.h

@@ -161,6 +161,9 @@ namespace persistent_data {
 				return raw_;
 			}
 
+			bool value_sizes_match() const;
+			std::string value_mismatch_string() const;
+
 		private:
 			static unsigned calc_max_entries(void);
 			void check_fits_within_block() const;

persistent-data/data-structures/btree.tcc

@@ -362,19 +362,31 @@ namespace persistent_data {
 		}
 	}
 
+	template <typename ValueTraits>
+	bool
+	node_ref<ValueTraits>::value_sizes_match() const {
+		return sizeof(typename ValueTraits::disk_type) == get_value_size();
+	}
+
+	template <typename ValueTraits>
+	std::string
+	node_ref<ValueTraits>::value_mismatch_string() const {
+		std::ostringstream out;
+		out << "value size mismatch: expected " << sizeof(typename ValueTraits::disk_type)
+		    << ", but got " << get_value_size()
+		    << ".  This is not the btree you are looking for." << std::endl;
+
+		return out.str();
+	}
+
 	template <typename ValueTraits>
 	void
 	node_ref<ValueTraits>::check_fits_within_block() const {
 		if (checked_)
 			return;
 
-		if (sizeof(typename ValueTraits::disk_type) != get_value_size()) {
+		if (!value_sizes_match())
-			std::ostringstream out;
+			throw std::runtime_error(value_mismatch_string());
-			out << "value size mismatch: expected " << sizeof(typename ValueTraits::disk_type)
-			    << ", but got " << get_value_size()
-			    << ".  This is not the btree you are looking for." << std::endl;
-			throw std::runtime_error(out.str());
-		}
 
 		unsigned max = calc_max_entries();
 

persistent-data/data-structures/btree_damage_visitor.h

@@ -210,6 +210,7 @@ namespace persistent_data {
 					    btree_detail::node_ref<block_traits> const &n) {
 				if (!already_visited(n) &&
 				    check_block_nr(n) &&
+				    check_value_size(n) &&
 				    check_max_entries(n) &&
 				    check_nr_entries(n, loc.is_sub_root()) &&
 				    check_ordered_keys(n) &&
@@ -229,6 +230,7 @@ namespace persistent_data {
 					btree_detail::node_ref<ValueTraits2> const &n) {
 				if (!already_visited(n) &&
 				    check_block_nr(n) &&
+				    check_value_size(n) &&
 				    check_max_entries(n) &&
 				    check_nr_entries(n, loc.is_sub_root()) &&
 				    check_ordered_keys(n) &&
@@ -275,6 +277,16 @@ namespace persistent_data {
 				return true;
 			}
 
+			template <typename node>
+			bool check_value_size(node const &n) {
+				if (!n.value_sizes_match()) {
+					report_damage(n.value_mismatch_string());
+					return false;
+				}
+
+				return true;
+			}
+
 			template <typename node>
 			bool check_max_entries(node const &n) {
 				size_t elt_size = sizeof(uint64_t) + n.get_value_size();