This is the source code snippet that is used for the serialization of block indexes (found in leveldb).

Block 478573 index is (as of my node's leveldb) 89af109c996d020000000020774f568005a00bf4ffed76b52e3a7e5e5140a5371834a00000000000000000009f5db27969fecc0ef71503279069b2df981ba545592a7b425f353b5060e77f3e7e13825935470118da70378e

Isn't NFile undefined (i.e. 0) in this case? (and NDataPos and NUndoPos too).

Whereas for block 478574 it is :

89af109c996e1d801886399fbf8017828daf5502000020dcc139c241e6315463dd82c89fc288de35f004c87816430000000000000000000f7f9503fc2daab46c4103516c386b1c5b2390e082af76ba8c49fb522d5e5b148b96805935470118ae6ba061

Which yields NFile = 953 and is correct.

Why block 478573 is not defined? And how to retrieve NFile and NDataPos in that case? I understand that the index is different for every node because it depends on the order the blocks were downloaded.