Module Fiber.FLS

Fiber local storage

Fiber local storage is intended for use as a low overhead storage mechanism for fiber extensions. For example, one might associate a priority value with each fiber for a scheduler that uses a priority queue or one might use FLS to store unique id values for fibers.

type fiber := t

Destructively substituted alias for Fiber.t.

type 'a t

Represents a key for storing values of type 'a in storage associated with fibers.

val create : unit -> 'a t

new_key initial allocates a new key for associating values in storage associated with fibers. The initial value for every fiber is either the given Constant or is Computed with the given function. If the initial value is a constant, no value needs to be stored unless the value is explicitly updated.

⚠️ New keys should not be created dynamically.

exception Not_set

Raised by get_exn in case value has not been set.

val get_exn : fiber -> 'a t -> 'a

get_exn fiber key returns the value associated with the key in the storage associated with the fiber or raises Not_set using raise_notrace.

⚠️ It is only safe to call get_exn from the fiber itself or when the fiber is known not to be running.

val get : fiber -> 'a t -> default:'a -> 'a

get fiber key ~default returns the value associated with the key in the storage associated with the fiber or the default value.

⚠️ It is only safe to call get from the fiber itself or when the fiber is known not to be running.

val set : fiber -> 'a t -> 'a -> unit

set fiber key value sets the value associated with the key to the given value in the storage associated with the fiber.

⚠️ It is only safe to call set from the fiber itself or when the fiber is known not to be running.

val remove : fiber -> 'a t -> unit

remove fiber key removes the value, if any, associated with the key from the storage associated with the fiber.

⚠️ It is only safe to call remove from the fiber itself or when the fiber is known not to be running.

val reserve : fiber -> 'a t -> unit

reserve fiber key ensures that sufficient space has been allocated to associate a value with the specified key such that a subsequent set with the key will not allocate.

ℹ️ This can be used to optimize the population of the FLS and to avoid performing memory allocations in critical sections.

⚠️ It is only safe to call reserve from the fiber itself or when the fiber is known not to be running.