Local Open Scope logic.
Definition Done (i:Z): int := Int.repr (digest_len*i).
Definition OUTpred PrkCont InfoCont sh z r cont p: mpred:=
data_at sh (tarray tuchar z) (sublist 0 z (map Vubyte (HKDF_expand PrkCont InfoCont cont))) p *
memory_block sh r (offset_val z p).
Definition PREVcont PRK INFO (i: Z): reptype (Tarray tuchar 32 noattr) :=
if zeq i 0 then list_repeat 32 Vundef
else (map Vubyte (Ti (CONT PRK) (CONT INFO) (Z.to_nat i))).

Lemma sublist_HKDF_expand5 PRK INFO l i
(Hl : if zeq i 0 then l = []
else PREVcont PRK INFO i = map Vubyte l)
(Hi : 0 <= i <= Byte.max_unsigned):
sublist 0 32 (HMAC256_functional_prog.HMAC256 ((l ++ CONT INFO) ++ [Byte.add (Byte.repr i) Byte.one]) (CONT PRK)) =
sublist (32 * i) (32 * i + 32) (HKDF_expand (CONT PRK) (CONT INFO) (32 * (i + 1))).