Fixpoint memory_block' (sh: share) (n: nat) (b: block) (i: Z) : mpred :=
  match n with
  | O => emp
  | S n' => mapsto_ sh (Tint I8 Unsigned noattr) (Vptr b (Ptrofs.repr i))
         * memory_block' sh n' b (i+1)
 end.Definition memory_block'_alt (sh: share) (n: nat) (b: block) (ofs: Z) : mpred :=
 if readable_share_dec sh 
 then VALspec_range (Z_of_nat n) sh (b, ofs)
 else nonlock_permission_bytes sh (b,ofs) (Z.of_nat n).

Lemma memory_block'_split: forall sh b ofs i j, 0 <= i <= j -> j <= j+ofs < Ptrofs.modulus -> memory_block' sh (nat_of_Z j) b ofs = memory_block' sh (nat_of_Z i) b ofs * memory_block' sh (nat_of_Z (j-i)) b (ofs+i).