module Weak = struct ... end
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
nth cell of
ar to be a
(full) pointer to
el;
Weak.set ar n None sets the
nth
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
nth 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
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).
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
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.
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. Raise Invalid_argument "Weak.fill"
if ofs and len do not designate a valid subarray 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.
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.