package iomux

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Module type
Class type

A direct binding of poll(2).

type t

Main type for a poller.

val create : ?maxfds:int -> unit -> t

create ?maxfds () creates a new poller.

val maxfds : t -> int

maxfds t is the maximum number of file descriptor slots allocated for t.

module Flags : sig ... end

The set of flags associated with a file descriptor event.

val has_ppoll : bool

has_ppoll is true if the system supports the ppoll(2) system call. Notably macos as of 2023 does not have it.

val invalid_fd : Unix.file_descr

invalid_fd is the Unix.file_descr of value -1.

type poll_timeout =
  1. | Infinite

    No timeout, wait forever

  2. | Nowait

    Don't block, return immediately

  3. | Milliseconds of int

    Block for at most int milliseconds


The timeout parameter for poll.

val poll : t -> int -> poll_timeout -> int

The actual poll(2) call

poll t nfds timeout polls for the first nfds, like the system call, invalid (-1) entries are ignored. The internal buffer is not modified after the call. It returns the number of ready file descriptors suitable to be used with iter_ready.

type ppoll_timeout =
  1. | Infinite

    No timeout, wait forever

  2. | Nowait

    Don't block, return immediately

  3. | Nanoseconds of int64

    Block for at most int64 nanoseconds


The timeout parameter for ppoll. Supports nanoseconds instead of milliseconds.

val ppoll : t -> int -> ppoll_timeout -> int list -> int

The actual ppoll(2) call

ppoll t nfds timeout sigmask is like poll but supports nanoseconds and a list of signals that are atomically masked during execution and restored uppon return. If the system does not has_ppoll this call will raise Unix.Unix_error with ENOSYS. You most likely want to use ppoll_or_poll, see below.

val ppoll_or_poll : t -> int -> ppoll_timeout -> int

A more portable ppoll(2) call

ppoll_or_poll t nfds tiemout is like ppoll if the system has_ppoll, otherwise the call is emulated via poll, notably the timeout is internally converted to milliseconds and there is no support for signal masking. You most likely want to use this instead of ppoll, the two calls are kept to prevent the user from expecting nanoseconds resolution from an emulated ppoll call.

val set_index : t -> int -> Unix.file_descr -> Flags.t -> unit

set_index t index fd flag modifies the internal buffer at index to listen to flag events of fd. This overwrites any previous value of flag and fd internally. invalid_fd (-1) can be used to deactivate the slot, but usage of invalidate_index is preferred.

val invalidate_index : t -> int -> unit

invalidate_index t index modifies the internal buffer by invalidating index. The kernel will ignore that slot. We also clear flags, just for kicks.

val get_revents : t -> int -> Flags.t

get_revents t index is the returned event flags set after a call to poll or ppoll.

val get_fd : t -> int -> Unix.file_descr

get_fd t index is the file descriptor associated with index.

val iter_ready : t -> int -> (int -> Unix.file_descr -> Flags.t -> unit) -> unit

iter_ready t nready fn scans the internal buffer for every ready file descriptor and calls fn index fd flags, the scanning is aborted after nready entries are found. Invalid file descriptors (set to -1 via invalidate_index) are skipped. Typical usage is that nready is the return of poll or ppoll. The internal buffer is left unmodified.