ocaml/otherlibs/threads/thread.mli

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(*                                                                     *)
(*                           Objective Caml                            *)
(*                                                                     *)
(*            Xavier Leroy, projet Cristal, INRIA Rocquencourt         *)
(*                                                                     *)
(*  Copyright 1996 Institut National de Recherche en Informatique et   *)
(*  en Automatique.  All rights reserved.  This file is distributed    *)
(*  under the terms of the GNU Library General Public License.         *)
(*                                                                     *)
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(* $Id$ *)

(* Module [Thread]: lightweight threads *)

type t
        (* The type of thread handles. *)

(** Thread creation and termination *)

val create : ('a -> 'b) -> 'a -> t
        (* [Thread.create funct arg] creates a new thread of control,
           in which the function application [funct arg]
           is executed concurrently with the other threads of the program.
           The application of [Thread.create]
           returns the handle of the newly created thread.
           The new thread terminates when the application [funct arg]
           returns, either normally or by raising an uncaught exception.
           In the latter case, the exception is printed on standard error,
           but not propagated back to the parent thread. Similarly, the
           result of the application [funct arg] is discarded and not
           directly accessible to the parent thread. *)
val self : unit -> t
        (* Return the thread currently executing. *)
external id : t -> int = "thread_id"
        (* Return the identifier of the given thread. A thread identifier
           is an integer that identifies uniquely the thread.
           It can be used to build data structures indexed by threads. *)
val exit : unit -> unit
        (* Terminate prematurely the currently executing thread. *)
val kill : t -> unit
        (* Terminate prematurely the thread whose handle is given.
           This functionality is available only with bytecode-level threads. *)

(** Suspending threads *)

val delay: float -> unit
        (* [delay d] suspends the execution of the calling thread for
           [d] seconds. The other program threads continue to run during
           this time. *)
val join : t -> unit
        (* [join th] suspends the execution of the calling thread
           until the thread [th] has terminated. *)
val wait_read : Unix.file_descr -> unit
val wait_write : Unix.file_descr -> unit
        (* Suspend the execution of the calling thread until at least
           one character is available for reading ([wait_read]) or
           one character can be written without blocking ([wait_write])
           on the given Unix file descriptor. *)
val wait_timed_read : Unix.file_descr -> timeout:float -> bool
val wait_timed_write : Unix.file_descr -> timeout:float -> bool
        (* Same as [wait_read] and [wait_write], but wait for at most
           the amount of time given as second argument (in seconds).
           Return [true] if the file descriptor is ready for input/output
           and [false] if the timeout expired. *)
val select :
  read:Unix.file_descr list -> write:Unix.file_descr list ->
  exn:Unix.file_descr list -> timeout:float ->
    Unix.file_descr list * Unix.file_descr list * Unix.file_descr list
        (* Suspend the execution of the calling thead until input/output
           becomes possible on the given Unix file descriptors.
           The arguments and results have the same meaning as for
           [Unix.select]. *)
val wait_pid : int -> int * Unix.process_status
        (* [wait_pid p] suspends the execution of the calling thread
           until the Unix process specified by the process identifier [p]
           terminates. A pid [p] of [-1] means wait for any child.
           A pid of [0] means wait for any child in the same process group
           as the current process. Negative pid arguments represent
           process groups. Returns the pid of the child caught and
           its termination status, as per [Unix.wait]. *)
val wait_signal : int list -> int
        (* [wait_signal sigs] suspends the execution of the calling thread
           until the process receives one of the signals specified in the
           list [sigs].  It then returns the number of the signal received.
           Signal handlers attached to the signals in [sigs] will not
           be invoked.  Do not call [wait_signal] concurrently 
           from several threads on the same signals. *)
val yield : unit -> unit
        (* Re-schedule the calling thread without suspending it.
           This function can be used to give scheduling hints,
           telling the scheduler that now is a good time to
           switch to other threads. *)

(*--*)

(* The following primitives provide the basis for implementing 
   synchronization functions between threads. Their direct use is
   discouraged, as they are very low-level and prone to race conditions
   and deadlocks. The modules [Mutex], [Condition] and [Event]
   provide higher-level synchronization primitives. *)

val critical_section: bool ref
        (* Setting this reference to [true] deactivate thread preemption
           (the timer interrupt that transfers control from thread to thread),
           causing the current thread to run uninterrupted until
           [critical_section] is reset to [false] or the current thread
           explicitely relinquishes control using [sleep], [delay],
           [wait_inchan] or [wait_descr]. *)
val sleep : unit -> unit
        (* Suspend the calling thread until another thread reactivates it
           using [wakeup]. Just before suspending the thread,
           [critical_section] is reset to [false]. Resetting
           [critical_section] and suspending the calling thread is an
           atomic operation. *)
val wakeup : t -> unit
        (* Reactivate the given thread. After the call to [wakeup],
           the suspended thread will resume execution at some future time. *)