+let chr (c:int) : char = Obj.magic (c land 0xff)
+let bit_vector_unsafe_set v i b =
+ let j = i lsr 3 in
+ let c = Char.code v.[j] in
+ let bit = int_of_bool b in
+ let mask = bit lsl (i land 7) in
+ if b then v.[j] <- chr (c lor mask) else v.[j] <- (chr (c land (lnot mask)))
+
+let bit_vector_create n =
+ let len = if n <= 0 then 0 else (n - 1) / 8 + 1 in
+ String.make len '\000'