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(***********************************************************************)
(* *)
(* Objective Caml *)
(* *)
(* Damien Doligez, projet Para, INRIA Rocquencourt *)
(* *)
(* Copyright 1997 Institut National de Recherche en Informatique et *)
(* en Automatique. All rights reserved. This file is distributed *)
(* under the terms of the GNU Library General Public License. *)
(* *)
(***********************************************************************)
(* $Id$ *)
(* Module [Weak]: arrays of weak pointers *)
type 'a t;;
(* The type of arrays of weak pointers (weak arrays). A weak
pointer is a value that the garbage collector may erase at
any time.
A weak pointer is said to be full if it points to a value,
empty if the value was erased by the GC.
*)
val create : int -> 'a t;;
(* [Weak.create n] returns a new weak array of length [n].
All the pointers are initially empty. Raise [Invalid_argument]
if [n] is negative or greater than [Sys.max_array_length-1].
*)
val length : 'a t -> int;;
(* [Weak.length ar] returns the length (number of elements) of
[ar].
*)
val set : 'a t -> int -> 'a option -> unit;;
(* [Weak.set ar n (Some el)] sets the [n]th cell of [ar] to be a
(full) pointer to [el]; [Weak.set ar n None] sets the [n]th
cell of [ar] to empty.
Raise [Invalid_argument "Weak.set"] if [n] is not in the range
0 to [Weak.length a - 1].
*)
val get : 'a t -> int -> 'a option;;
(* [Weak.get ar n] returns None if the [n]th cell of [ar] is
empty, [Some x] (where [x] is the value) if it is full.
Raise [Invalid_argument "Weak.get"] if [n] is not in the range
0 to [Weak.length a - 1].
*)
val get_copy : 'a t -> int -> 'a option;;
(* [Weak.get_copy ar n] returns None if the [n]th cell of [ar] is
empty, [Some x] (where [x] is a (shallow) copy of the value) if
it is full.
In addition to pitfalls with mutable values, the interesting
difference with [get] is that [get_copy] does not prevent
the incremental GC from erasing the value in its current cycle
([get] may delay the erasure to the next GC cycle).
Raise [Invalid_argument "Weak.get"] if [n] is not in the range
0 to [Weak.length a - 1].
*)
val check: 'a t -> int -> bool;;
(* [Weak.check ar n] returns [true] if the [n]th cell of [ar] is
full, [false] if it is empty. Note that even if [Weak.check ar n]
returns [true], a subsequent [Weak.get ar n] can return [None].
*)
val fill: 'a t -> pos:int -> len:int -> 'a option -> unit;;
(* [Weak.fill ar ofs len el] sets to [el] all pointers of [ar] from
[ofs] to [ofs + len - 1]. Raise [Invalid_argument "Weak.fill"]
if [ofs] and [len] do not designate a valid subarray of [a].
*)
val blit : src:'a t -> src_pos:int ->
dst:'a t -> dst_pos:int -> len:int -> unit;;
(* [Weak.blit ar1 off1 ar2 off2 len] copies [len] weak pointers
from [ar1] (starting at [off1]) to [ar2] (starting at [off2]).
It works correctly even if [ar1] and [ar2] are the same.
Raise [Invalid_argument "Weak.blit"] if [off1] and [len] do
not designate a valid subarray of [ar1], or if [off2] and [len]
do not designate a valid subarray of [ar2].
*)
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