(*
   Wojciech Muła, $Id: myhash.ml,v 1.3 2006-06-04 08:34:03 wojtek Exp $
 *)

let itertop f hash =
	let prev = ref None in
	let aux key value =
		let prev' = !prev in
		begin
			prev := Some key;
			match prev' with
			  None      -> f key value
			| Some key' -> if key' <> key then f key value
		end;
	in
		Hashtbl.iter aux hash

let foldtop f hash init =
	let prev = ref None in
	let aux key value acc =
		let prev' = !prev in
		begin
			prev := Some key;
			match prev' with
			  None      -> f key value acc
			| Some key' -> if key' <> key then
			                  f key value acc
				       else
				          acc
		end;
	in
		Hashtbl.fold aux hash init

let keys hash =
	Hashtbl.fold (fun key value list -> key::list) hash []

let values hash =
	Hashtbl.fold (fun key value list -> value::list) hash []

let items hash =
	Hashtbl.fold (fun key value list -> (key,value)::list) hash []

let from_items2 l =
	let h = ref (Hashtbl.create (List.length l)) in
	let rec worker = function
		| []        -> ()
		| (k,v)::xs -> Hashtbl.add !h k v;
		               worker xs
	in
		worker l; !h

let from_items keys values =
	let h = ref (Hashtbl.create (List.length keys)) in
	let rec worker = function
		| ([], [])       -> ()
		| (_ , [])       -> failwith "from_items: v shorten then k"
		| ([], _ )       -> failwith "from_items: k shorten then v"
		| (k::ks, v::vs) -> Hashtbl.add !h k v;
		                    worker (ks, vs)
	in
		worker (keys,values); !h

let findVariant h x =
	try Some (Hashtbl.find h x) with Not_found -> None

let set_default h x d =
	try
		Hashtbl.find h x
	with
		Not_found -> Hashtbl.add h x d; d

let remove_all hash key =
	let l = Hashtbl.find_all hash key in
	let n = List.length l in
	for i = 0 to n do
		Hashtbl.remove hash key
	done;
	l

let replace_all hash key value =
	let removed = remove_all hash key in
		Hashtbl.add hash key value;
		removed

let reverse_hash hash =
	let i  = items hash in
	let i' = List.map (fun (k,v) -> (v,k)) i in
		from_items2 i'