(* Modified for Poly/ML from SML/NJ Library version 0.2
*
* COPYRIGHT (c) 1992 by AT&T Bell Laboratories.
* See file mosml/copyrght/copyrght.att for details.
*
* Original author: John Reppy, AT&T Bell Laboratories, Murray Hill, NJ 07974
* Current version from the Moscow ML distribution, copied by permission.
*)
(* Polyhash -- polymorphic hashtables as in the SML/NJ Library *)
signature Polyhash =
sig
type ('key, 'data) hash_table
val mkTable : ('_key -> int) * ('_key * '_key -> bool) -> int * exn
-> ('_key, '_data) hash_table
val numItems : ('key, 'data) hash_table -> int
val insert : ('_key, '_data) hash_table -> '_key * '_data -> unit
val peekInsert : ('_key, '_data) hash_table -> '_key * '_data
-> '_data option
val find : ('key, 'data) hash_table -> 'key -> 'data
val peek : ('key, 'data) hash_table -> 'key -> 'data option
val remove : ('key, 'data) hash_table -> 'key -> 'data
val listItems : ('key, 'data) hash_table -> ('key * 'data) list
val apply : ('key * 'data -> unit) -> ('key, 'data) hash_table -> unit
val map : ('_key * 'data -> '_res) -> ('_key, 'data) hash_table
-> ('_key, '_res) hash_table
val filter : ('key * 'data -> bool) -> ('key, 'data) hash_table -> unit
val transform : ('data -> '_res) -> ('_key, 'data) hash_table
-> ('_key, '_res) hash_table
val copy : ('_key, '_data) hash_table -> ('_key, '_data) hash_table
val bucketSizes : ('key, 'data) hash_table -> int list
(*Additions due to L. C. Paulson and Jia Meng*)
val hashw : word * word -> word
val hashw_char : Char.char * word -> word
val hashw_int : int * word -> word
val hashw_vector : word Vector.vector * word -> word
val hashw_string : string * word -> word
val hashw_strings : string list * word -> word
val hash_string : string -> int
(*
[('key, 'data) hash_table] is the type of hashtables with keys of type
'key and data values of type 'data.
[mkTable (hashVal, sameKey) (sz, exc)] returns a new hashtable,
using hash function hashVal and equality predicate sameKey. The sz
is a size hint, and exc is the exception raised by function find.
It must be the case that sameKey(k1, k2) implies hashVal(k1) =
hashVal(k2) for all k1,k2.
[numItems htbl] is the number of items in the hash table.
[insert htbl (k, d)] inserts data d for key k. If k already had an
item associated with it, then the old item is overwritten.
[find htbl k] returns d, where d is the data item associated with key k,
or raises the exception (given at creation of htbl) if there is no such d.
[peek htbl k] returns SOME d, where d is the data item associated with
key k, or NONE if there is no such d.
[peekInsert htbl (k, d)] inserts data d for key k, if k is not
already in the table, returning NONE. If k is already in the
table, and the associated data value is d', then returns SOME d'
and leaves the table unmodified.
[remove htbl k] returns d, where d is the data item associated with key k,
removing d from the table; or raises the exception if there is no such d.
[listItems htbl] returns a list of the (key, data) pairs in the hashtable.
[apply f htbl] applies function f to all (key, data) pairs in the
hashtable, in some order.
[map f htbl] returns a new hashtable, whose data items have been
obtained by applying f to the (key, data) pairs in htbl. The new
tables have the same keys, hash function, equality predicate, and
exception, as htbl.
[filter p htbl] deletes from htbl all data items which do not
satisfy predicate p.
[transform f htbl] as map, but only the (old) data values are used
when computing the new data values.
[copy htbl] returns a complete copy of htbl.
[bucketSizes htbl] returns a list of the sizes of the buckets.
This is to allow users to gauge the quality of their hashing
function.
*)
end
structure Polyhash :> Polyhash =
struct
datatype ('key, 'data) bucket_t
= NIL
| B of int * 'key * 'data * ('key, 'data) bucket_t
datatype ('key, 'data) hash_table =
HT of {hashVal : 'key -> int,
sameKey : 'key * 'key -> bool,
not_found : exn,
table : ('key, 'data) bucket_t Array.array ref,
n_items : int ref}
local
(*
prim_val andb_ : int -> int -> int = 2 "and";
prim_val lshift_ : int -> int -> int = 2 "shift_left";
*)
fun andb_ x y = Word.toInt (Word.andb (Word.fromInt x, Word.fromInt y));
fun lshift_ x y = Word.toInt (Word.<< (Word.fromInt x, Word.fromInt y));
in
fun index (i, sz) = andb_ i (sz-1)
(* find smallest power of 2 (>= 32) that is >= n *)
fun roundUp n =
let fun f i = if (i >= n) then i else f (lshift_ i 1)
in f 32 end
end;
(* Create a new table; the int is a size hint and the exception
* is to be raised by find.
*)
fun mkTable (hashVal, sameKey) (sizeHint, notFound) = HT{
hashVal=hashVal,
sameKey=sameKey,
not_found = notFound,
table = ref (Array.array(roundUp sizeHint, NIL)),
n_items = ref 0
};
(* conditionally grow a table *)
fun growTable (HT{table, n_items, ...}) = let
val arr = !table
val sz = Array.length arr
in
if (!n_items >= sz)
then let
val newSz = sz+sz
val newArr = Array.array (newSz, NIL)
fun copy NIL = ()
| copy (B(h, key, v, rest)) = let
val indx = index (h, newSz)
in
Array.update (newArr, indx,
B(h, key, v, Array.sub(newArr, indx)));
copy rest
end
fun bucket n = (copy (Array.sub(arr, n)); bucket (n+1))
in
(bucket 0) handle _ => (); (* FIXME avoid handle _ *)
table := newArr
end
else ()
end (* growTable *);
(* Insert an item. If the key already has an item associated with it,
* then the old item is discarded.
*)
fun insert (tbl as HT{hashVal, sameKey, table, n_items, ...}) (key, item) =
let
val arr = !table
val sz = Array.length arr
val hash = hashVal key
val indx = index (hash, sz)
fun look NIL = (
Array.update(arr, indx, B(hash, key, item, Array.sub(arr, indx)));
inc n_items;
growTable tbl;
NIL)
| look (B(h, k, v, r)) = if ((hash = h) andalso sameKey(key, k))
then B(hash, key, item, r)
else (case (look r)
of NIL => NIL
| rest => B(h, k, v, rest)
(* end case *))
in
case (look (Array.sub (arr, indx)))
of NIL => ()
| b => Array.update(arr, indx, b)
end;
(* Insert an item if not there already; if it is there already,
then return the old data value and leave the table unmodified..
*)
fun peekInsert (tbl as HT{hashVal, sameKey, table, n_items, ...}) (key, item) =
let val arr = !table
val sz = Array.length arr
val hash = hashVal key
val indx = index (hash, sz)
fun look NIL =
(Array.update(arr, indx, B(hash, key, item,
Array.sub(arr, indx)));
inc n_items;
growTable tbl;
NONE)
| look (B(h, k, v, r)) =
if hash = h andalso sameKey(key, k) then SOME v
else look r
in
look (Array.sub (arr, indx))
end;
(* find an item, the table's exception is raised if the item doesn't exist *)
fun find (HT{hashVal, sameKey, table, not_found, ...}) key = let
val arr = !table
val sz = Array.length arr
val hash = hashVal key
val indx = index (hash, sz)
fun look NIL = raise not_found
| look (B(h, k, v, r)) = if ((hash = h) andalso sameKey(key, k))
then v
else look r
in
look (Array.sub (arr, indx))
end;
(* look for an item, return NONE if the item doesn't exist *)
fun peek (HT{hashVal, sameKey, table, ...}) key = let
val arr = !table
val sz = Array.length arr
val hash = hashVal key
val indx = index (hash, sz)
fun look NIL = NONE
| look (B(h, k, v, r)) = if ((hash = h) andalso sameKey(key, k))
then SOME v
else look r
in
look (Array.sub (arr, indx))
end;
(* Remove an item. The table's exception is raised if
* the item doesn't exist.
*)
fun remove (HT{hashVal, sameKey, not_found, table, n_items}) key = let
val arr = !table
val sz = Array.length arr
val hash = hashVal key
val indx = index (hash, sz)
fun look NIL = raise not_found
| look (B(h, k, v, r)) = if ((hash = h) andalso sameKey(key, k))
then (v, r)
else let val (item, r') = look r in (item, B(h, k, v, r')) end
val (item, bucket) = look (Array.sub (arr, indx))
in
Array.update (arr, indx, bucket);
n_items := !n_items - 1;
item
end (* remove *);
(* Return the number of items in the table *)
fun numItems (HT{n_items, ...}) = !n_items
(* return a list of the items in the table *)
fun listItems (HT{table = ref arr, n_items, ...}) = let
fun f (_, l, 0) = l
| f (~1, l, _) = l
| f (i, l, n) = let
fun g (NIL, l, n) = f (i-1, l, n)
| g (B(_, k, v, r), l, n) = g(r, (k, v)::l, n-1)
in
g (Array.sub(arr, i), l, n)
end
in
f ((Array.length arr) - 1, [], !n_items)
end (* listItems *);
(* Apply a function to the entries of the table *)
fun apply f (HT{table, ...}) = let
fun appF NIL = ()
| appF (B(_, key, item, rest)) = (
f (key, item);
appF rest)
val arr = !table
val sz = Array.length arr
fun appToTbl i = if (i < sz)
then (appF (Array.sub (arr, i)); appToTbl(i+1))
else ()
in
appToTbl 0
end (* apply *);
(* Map a table to a new table that has the same keys and exception *)
fun map f (HT{hashVal, sameKey, table, n_items, not_found}) = let
fun mapF NIL = NIL
| mapF (B(hash, key, item, rest)) =
B(hash, key, f (key, item), mapF rest)
val arr = !table
val sz = Array.length arr
val newArr = Array.array (sz, NIL)
fun mapTbl i = if (i < sz)
then (
Array.update(newArr, i, mapF (Array.sub(arr, i)));
mapTbl (i+1))
else ()
in
mapTbl 0;
HT{hashVal=hashVal,
sameKey=sameKey,
table = ref newArr,
n_items = ref(!n_items),
not_found = not_found}
end (* transform *);
(* remove any hash table items that do not satisfy the given
* predicate.
*)
fun filter pred (HT{table, n_items, not_found, ...}) = let
fun filterP NIL = NIL
| filterP (B(hash, key, item, rest)) = if (pred(key, item))
then B(hash, key, item, filterP rest)
else filterP rest
val arr = !table
val sz = Array.length arr
fun filterTbl i = if (i < sz)
then (
Array.update (arr, i, filterP (Array.sub (arr, i)));
filterTbl (i+1))
else ()
in
filterTbl 0
end (* filter *);
(* Map a table to a new table that has the same keys, exception,
hash function, and equality function *)
fun transform f (HT{hashVal, sameKey, table, n_items, not_found}) = let
fun mapF NIL = NIL
| mapF (B(hash, key, item, rest)) = B(hash, key, f item, mapF rest)
val arr = !table
val sz = Array.length arr
val newArr = Array.array (sz, NIL)
fun mapTbl i = if (i < sz)
then (
Array.update(newArr, i, mapF (Array.sub(arr, i)));
mapTbl (i+1))
else ()
in
mapTbl 0;
HT{hashVal=hashVal,
sameKey=sameKey,
table = ref newArr,
n_items = ref(!n_items),
not_found = not_found}
end (* transform *);
(* Create a copy of a hash table *)
fun copy (HT{hashVal, sameKey, table, n_items, not_found}) = let
val arr = !table
val sz = Array.length arr
val newArr = Array.array (sz, NIL)
fun mapTbl i = (
Array.update (newArr, i, Array.sub(arr, i));
mapTbl (i+1))
in
(mapTbl 0) handle _ => (); (* FIXME avoid handle _ *)
HT{hashVal=hashVal,
sameKey=sameKey,
table = ref newArr,
n_items = ref(!n_items),
not_found = not_found}
end (* copy *);
(* returns a list of the sizes of the various buckets. This is to
* allow users to gauge the quality of their hashing function.
*)
fun bucketSizes (HT{table = ref arr, ...}) = let
fun len (NIL, n) = n
| len (B(_, _, _, r), n) = len(r, n+1)
fun f (~1, l) = l
| f (i, l) = f (i-1, len (Array.sub (arr, i), 0) :: l)
in
f ((Array.length arr)-1, [])
end
(*Added by lcp.
This is essentially the described in Compilers:
Principles, Techniques, and Tools, by Aho, Sethi and Ullman.*)
(*This hash function is recommended in Compilers: Principles, Techniques, and
Tools, by Aho, Sethi and Ullman. The hashpjw function, which they particularly
recommend, triggers a bug in versions of Poly/ML up to 4.2.0.*)
fun hashw (u,w) = Word.+ (u, Word.*(0w65599,w))
fun hashw_char (c,w) = hashw (Word.fromInt (Char.ord c), w);
fun hashw_int (i,w) = hashw (Word.fromInt i, w);
fun hashw_vector (v,w) = Vector.foldl hashw w v;
fun hashw_string (s:string, w) = CharVector.foldl hashw_char w s;
fun hashw_strings (ss, w) = List.foldl hashw_string w ss;
fun hash_string s = Word.toIntX (hashw_string(s,0w0));
end