btrfs-tree: add root refs and extent flags fields

Lazily filling in accessor methods for btrfs objects as needed by bees.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

include/crucible/btrfs-tree.h

@@ -64,11 +64,13 @@ namespace crucible {
 		/// @{ Extent items (EXTENT_ITEM)
 		uint64_t extent_begin() const;
 		uint64_t extent_end() const;
+		uint64_t extent_flags() const;
 		uint64_t extent_generation() const;
 		/// @}
 
 		/// @{ Root items
 		uint64_t root_flags() const;
+		uint64_t root_refs() const;
 		/// @}
 
 		/// @{ Root backref items.

lib/btrfs-tree.cc

@@ -22,6 +22,13 @@ namespace crucible {
 		return m_objectid + m_offset;
 	}
 
+	uint64_t
+	BtrfsTreeItem::extent_flags() const
+	{
+		THROW_CHECK1(invalid_argument, btrfs_search_type_ntoa(m_type), m_type == BTRFS_EXTENT_ITEM_KEY);
+		return btrfs_get_member(&btrfs_extent_item::flags, m_data);
+	}
+
 	uint64_t
 	BtrfsTreeItem::extent_generation() const
 	{
@@ -61,6 +68,13 @@ namespace crucible {
 		return btrfs_get_member(&btrfs_root_item::flags, m_data);
 	}
 
+	uint64_t
+	BtrfsTreeItem::root_refs() const
+	{
+		THROW_CHECK1(invalid_argument, btrfs_search_type_ntoa(m_type), m_type == BTRFS_ROOT_ITEM_KEY);
+		return btrfs_get_member(&btrfs_root_item::refs, m_data);
+	}
+
 	ostream &
 	operator<<(ostream &os, const BtrfsTreeItem &bti)
 	{