module Weak:sig..end
Arrays of weak pointers and hash sets 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 whenever the value is not used any more (through normal pointers) by the program. Note that finalisation functions are run before the weak pointers are erased, because 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:
output_value
nor the functions of the Marshal module.val create : int -> 'a tWeak.create n returns a new weak array of length n.
All the pointers are initially empty.
Invalid_argument if n is not comprised between zero and
Obj.Ephemeron.max_ephe_length (limits included).val length : 'a t -> intWeak.length ar returns the length (number of elements) of
ar.
val set : 'a t -> int -> 'a option -> unitWeak.set ar n (Some el) sets the nth cell of ar to be a
(full) pointer to el; Weak.set ar n None sets the nth
cell of ar to empty.
Invalid_argument if n is not in the range
0 to Weak.length ar - 1.val get : 'a t -> int -> 'a optionWeak.get ar n returns None if the nth cell of ar is
empty, Some x (where x is the value) if it is full.
Invalid_argument if n is not in the range
0 to Weak.length ar - 1.val get_copy : 'a t -> int -> 'a optionWeak.get_copy ar n returns None if the nth 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).
Invalid_argument if n is not in the range
0 to Weak.length ar - 1.
If the element is a custom block it is not copied.val check : 'a t -> int -> boolWeak.check ar n returns true if the nth 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.
Invalid_argument if n is not in the range
0 to Weak.length ar - 1.val fill : 'a t -> int -> int -> 'a option -> unitWeak.fill ar ofs len el sets to el all pointers of ar from
ofs to ofs + len - 1.
Invalid_argument if ofs and len do not designate a valid subarray of ar.val blit : 'a t -> int -> 'a t -> int -> int -> unitWeak.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.
Invalid_argument 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.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 inducing 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.
Unsynchronized accesses
Unsynchronized accesses to weak hash sets are a programming error.
Unsynchronized accesses to a weak hash set may lead to an invalid weak hash
set state. Thus, concurrent accesses to weak hash sets must be synchronized
(for instance with a Mutex.t).
module type S =sig..end
The output signature of the functor Weak.Make.
module Make:
Functor building an implementation of the weak hash set structure.