Stdlib.Weak(3o) OCaml library Stdlib.Weak(3o)
NAME
Stdlib.Weak - no description
Module
Module Stdlib.Weak
Documentation
Module Weak
: (module Stdlib__Weak)
Low-level functions
type 'a t
The type of arrays of weak pointers (weak arrays). A weak pointer is a
value that the garbage collector may erase whenever the value is not
used any more (through normal pointers) by the program. Note that fi-
nalisation functions are run before the weak pointers are erased, be-
cause the finalisation functions can make values alive again (before
4.03 the finalisation functions were run after).
A weak pointer is said to be full if it points to a value, empty if the
value was erased by the GC.
Notes:
-Integers are not allocated and cannot be stored in weak arrays.
-Weak arrays cannot be marshaled using output_value nor the functions
of the Marshal module.
val create : int -> 'a t
Weak.create n returns a new weak array of length n . All the pointers
are initially empty.
Raises Invalid_argument if n is not comprised between zero and
Obj.Ephemeron.max_ephe_length (limits included).
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.
Raises Invalid_argument 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.
Raises Invalid_argument 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).
Raises Invalid_argument if n is not in the range 0 to Weak.length a - 1
.
If the element is a custom block it is not copied.
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 subse-
quent Weak.get ar n can return None .
val fill : 'a t -> int -> int -> 'a option -> unit
Weak.fill ar ofs len el sets to el all pointers of ar from ofs to ofs +
len - 1 .
Raises Invalid_argument if ofs and len do not designate a valid subar-
ray of a .
val blit : 'a t -> int -> 'a t -> int -> 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.
Raises Invalid_argument if off1 and len do not designate a valid subar-
ray of ar1 , or if off2 and len do not designate a valid subarray of
ar2 .
Weak hash sets
A weak hash set is a hashed set of values. Each value may magically
disappear from the set when it is not used by the rest of the program
any more. This is normally used to share data structures without in-
ducing memory leaks. Weak hash sets are defined on values from a
Hashtbl.HashedType module; the equal relation and hash function are
taken from that module. We will say that v is an instance of x if
equal x v is true .
The equal relation must be able to work on a shallow copy of the values
and give the same result as with the values themselves.
module type S = sig end
The output signature of the functor Weak.Make .
module Make : functor (H : Hashtbl.HashedType) -> sig end
Functor building an implementation of the weak hash set structure.
H.equal can't be the physical equality, since only shallow copies of
the elements in the set are given to it.
OCamldoc 2023-02-12 Stdlib.Weak(3o)
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