+ abort Forbidden [] Nothing
+ else
+ foundNoEntity Nothing
+
+
+-- |Computation of @'generateETagFromFile' fpath@ generates a strong
+-- entity tag from a file. The file doesn't necessarily have to be a
+-- regular file; it may be a FIFO or a device file. The tag is made of
+-- inode ID, size and modification time.
+--
+-- Note that the tag is not strictly strong because the file could be
+-- modified twice at a second without changing inode ID or size, but
+-- it's not really possible to generate a strict strong ETag from a
+-- file since we don't want to simply grab the entire file and use it
+-- as an ETag. It is indeed possible to hash it with SHA-1 or MD5 to
+-- increase strictness, but it's too inefficient if the file is really
+-- large (say, 1 TiB).
+generateETagFromFile ∷ FilePath → IO ETag