Weak - Arrays of weak pointers and hash sets of weak pointers.

       Module Weak
        : sigend

       Arrays of weak pointers and hash sets of weak pointers.

   Low-levelfunctionstype!'at

       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.

       valcreate : int->'atWeak.createn returns a new weak array of length n .  All the pointers are initially empty.

       RaisesInvalid_argument if n is not comprised  between  zero  and  Obj.Ephemeron.max_ephe_length  (limits
       included).

       vallength : 'at->intWeak.lengthar returns the length (number of elements) of ar .

       valset : 'at->int->'aoption->unitWeak.setarn(Someel) sets the n th cell of ar to be a (full) pointer to el ; Weak.setarnNone sets
       the n th cell of ar to empty.

       RaisesInvalid_argument if n is not in the range 0 to Weak.lengthar-1 .

       valget : 'at->int->'aoptionWeak.getarn returns None if the n th cell of ar is empty, Somex (where x is the value) if it is full.

       RaisesInvalid_argument if n is not in the range 0 to Weak.lengthar-1 .

       valget_copy : 'at->int->'aoptionWeak.get_copyarn returns None if the n th cell of ar is empty, Somex (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).

       RaisesInvalid_argument if n is not in the range 0 to Weak.lengthar-1 .

       If the element is a custom block it is not copied.

       valcheck : 'at->int->boolWeak.checkarn  returns  true if the n th cell of ar is full, false if it is empty.  Note that even if
       Weak.checkarn returns true , a subsequent Weak.getarn can return None .

       RaisesInvalid_argument if n is not in the range 0 to Weak.lengthar-1 .

       valfill : 'at->int->int->'aoption->unitWeak.fillarofslenel sets to el all pointers of ar from ofs to ofs+len-1 .

       RaisesInvalid_argument if ofs and len do not designate a valid subarray of ar .

       valblit : 'at->int->'at->int->int->unitWeak.blitar1off1ar2off2len 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.

       RaisesInvalid_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 .

   Weakhashsets
       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 equalxv 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 ).

       moduletypeS=sigend

       The output signature of the functor Weak.Make .

       moduleMake:(H:Hashtbl.HashedType)->sigend

       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                                           2025-06-12                                           Weak(3o)

       Module   Weak

       Weak - Arrays of weak pointers and hash sets of weak pointers.