Copyright 1996-2003 John D. Polstra.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgment:
* This product includes software developed by John D. Polstra.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* $Id: BackoffTimer.m3.html,v 1.3 2010-04-29 17:17:57 wagner Exp $
MODULE BackoffTimer;
IMPORT Random, Thread, Time;
REVEAL
T = BRANDED OBJECT
min, max: Time.T;
backoff: REAL;
jitter: REAL;
random: Random.T;
interval: Time.T;
END;
PROCEDURE New(min, max: Time.T;
backoff: REAL;
jitter: REAL): T =
VAR
bt: T;
BEGIN
bt := NEW(T,
min := min,
max := max,
backoff := backoff,
jitter := jitter,
random := NEW(Random.Default).init(),
interval := min);
AddJitter(bt);
RETURN bt;
END New;
PROCEDURE Pause(bt: T) =
BEGIN
Thread.Pause(bt.interval);
Update(bt);
END Pause;
PROCEDURE AlertPause(bt: T)
RAISES {Thread.Alerted} =
BEGIN
Thread.AlertPause(bt.interval);
Update(bt);
END AlertPause;
PROCEDURE Get(bt: T): Time.T =
BEGIN
RETURN bt.interval;
END Get;
PROCEDURE AddJitter(bt: T) =
BEGIN
WITH mag = FLOAT(bt.jitter, LONGREAL) * bt.interval DO
bt.interval := bt.interval + bt.random.longreal(-mag, mag);
END;
END AddJitter;
PROCEDURE Update(bt: T) =
BEGIN
bt.interval := MIN(bt.interval * FLOAT(bt.backoff, LONGREAL), bt.max);
AddJitter(bt);
END Update;
BEGIN
END BackoffTimer.