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|
(* Hash tables *)
(* We do dynamic hashing, and we double the size of the table when
buckets become too long, but without re-hashing the elements. *)
type ('a, 'b) t =
{ mutable max_len: int; (* max length of a bucket *)
mutable data: ('a, 'b) bucketlist array } (* the buckets *)
and ('a, 'b) bucketlist =
Empty
| Cons of 'a * 'b * ('a, 'b) bucketlist
let new initial_size =
{ max_len = 2; data = Array.new initial_size Empty }
let clear h =
for i = 0 to Array.length h.data - 1 do
h.data.(i) <- Empty
done
let resize h =
let n = Array.length h.data in
let newdata = Array.new (n+n) Empty in
Array.blit h.data 0 newdata 0 n;
Array.blit h.data 0 newdata n n;
h.data <- newdata;
h.max_len <- 2 * h.max_len
let rec bucket_too_long n bucket =
if n < 0 then true else
match bucket with
Empty -> false
| Cons(_,_,rest) -> bucket_too_long (pred n) rest
external hash_param : int -> int -> 'a -> int = "hash_univ_param" "noalloc"
let add h key info =
let i = (hash_param 10 100 key) mod (Array.length h.data) in
let bucket = Cons(key, info, h.data.(i)) in
h.data.(i) <- bucket;
if bucket_too_long h.max_len bucket then resize h
let remove h key =
let rec remove_bucket = function
Empty ->
Empty
| Cons(k, i, next) ->
if k = key then next else Cons(k, i, remove_bucket next) in
let i = (hash_param 10 100 key) mod (Array.length h.data) in
h.data.(i) <- remove_bucket h.data.(i)
let find h key =
match h.data.((hash_param 10 100 key) mod (Array.length h.data)) with
Empty -> raise Not_found
| Cons(k1, d1, rest1) ->
if key = k1 then d1 else
match rest1 with
Empty -> raise Not_found
| Cons(k2, d2, rest2) ->
if key = k2 then d2 else
match rest2 with
Empty -> raise Not_found
| Cons(k3, d3, rest3) ->
if key = k3 then d3 else begin
let rec find = function
Empty ->
raise Not_found
| Cons(k, d, rest) ->
if key = k then d else find rest
in find rest3
end
let find_all h key =
let rec find_in_bucket = function
Empty ->
[]
| Cons(k, d, rest) ->
if k = key then d :: find_in_bucket rest else find_in_bucket rest in
find_in_bucket h.data.((hash_param 10 100 key) mod (Array.length h.data))
let iter f h =
let len = Array.length h.data in
for i = 0 to Array.length h.data - 1 do
let rec do_bucket = function
Empty ->
()
| Cons(k, d, rest) ->
if (hash_param 10 100 k) mod len = i
then begin f k d; do_bucket rest end
else do_bucket rest in
do_bucket h.data.(i)
done
let hash x = hash_param 50 500 x
|
