A pool of resources.
This is useful to manage a collection of resources where creating new ones is expensive and so you want to reuse them where possible.
Example:
let buffer_pool = Eio.Pool.create 10 (fun () -> Bytes.create 1024) in
Eio.Pool.use buffer_pool (fun buf -> ...)Note: If you just need to limit how many resources are in use, it is simpler to use Eio.Semaphore instead.
val create :
?validate:('a -> bool) ->
?dispose:('a -> unit) ->
int ->
(unit -> 'a) ->
'a tcreate n alloc is a fresh pool which allows up to n resources to be live at a time. It uses alloc to create new resources as needed. If alloc raises an exception then that use fails, but future calls to use will retry.
The alloc function is called in the context of the fiber trying to use the pool. If the pool is shared between domains and the resources are attached to a switch, this might cause trouble (since switches can't be shared between domains). You might therefore want to make alloc request a resource from the main domain rather than creating one itself.
You should also take care about handling cancellation in alloc, since resources are typically attached to a switch with the lifetime of the pool, meaning that if alloc fails then they won't be freed automatically until the pool itself is finished.
val use : 'a t -> ('a -> 'b) -> 'buse t fn waits for some resource x to be available and then runs f x. Afterwards (on success or error), x is returned to the pool.