oracular (3) Stdlib.Weak.3o.gz

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
       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:

       -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 ar - 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 ar - 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 ar - 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 subsequent Weak.get ar n can return None .

       Raises Invalid_argument if n is not in the range 0 to Weak.length ar - 1 .

       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 subarray of ar .

       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 subarray 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
       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 (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.