/*
* Created on 18-Sep-2004
* Created by Paul Gardner
* Copyright (C) 2004, 2005, 2006 Aelitis, All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* AELITIS, SAS au capital de 46,603.30 euros
* 8 Allee Lenotre, La Grille Royale, 78600 Le Mesnil le Roi, France.
*
*/
package org.gudy.azureus2.core3.util;
/**
* @author parg
*
*/
public class
AESemaphore
extends AEMonSem
{
private int dont_wait = 0;
private int total_reserve = 0;
private int total_release = 0;
private boolean released_forever = false;
protected Thread latest_waiter;
public
AESemaphore(
String _name )
{
this( _name, 0 );
}
public
AESemaphore(
String _name,
int count )
{
super( _name, false );
dont_wait = count;
total_release = count;
}
public void
reserve()
{
if ( !reserve(0)){
Debug.out( "AESemaphore: reserve completed without acquire [" + getString() + "]" );
}
}
public boolean
reserve(
long millis )
{
return( reserveSupport( millis, 1 ) == 1 );
}
public boolean
reserveIfAvailable()
{
synchronized(this){
if ( released_forever || dont_wait > 0 ){
reserve();
return( true );
}else{
return( false );
}
}
}
public int
reserveSet(
int max_to_reserve,
long millis )
{
return( reserveSupport( millis, max_to_reserve));
}
public int
reserveSet(
int max_to_reserve )
{
return( reserveSupport( 0, max_to_reserve));
}
protected int
reserveSupport(
long millis,
int max_to_reserve )
{
if ( DEBUG ){
super.debugEntry();
}
synchronized(this){
entry_count++;
//System.out.println( name + "::reserve");
if ( released_forever ){
return(1);
}
if ( dont_wait == 0 ){
try{
waiting++;
latest_waiter = Thread.currentThread();
if ( waiting > 1 ){
// System.out.println( "AESemaphore: " + name + " contended" );
}
if ( millis == 0 ){
// we can get spurious wakeups (see Object javadoc) so we need to guard against
// their possibility
int spurious_count = 0;
while( true ){
wait();
if ( total_reserve == total_release ){
spurious_count++;
if ( spurious_count > 1024 ){
Debug.out( "AESemaphore: spurious wakeup limit exceeded" );
throw( new Throwable( "die die die" ));
}else{
// Debug.out("AESemaphore: spurious wakeup, ignoring" );
}
}else{
break;
}
}
}else{
// we don't hugely care about spurious wakeups here, it'll just appear
// as a failed reservation a bit early
wait(millis);
}
if ( total_reserve == total_release ){
// here we have timed out on the wait without acquiring
waiting--;
return( 0 );
}
total_reserve++;
return( 1 );
}catch( Throwable e ){
waiting--;
Debug.out( "**** semaphore operation interrupted ****" );
throw( new RuntimeException("Semaphore: operation interrupted", e ));
}finally{
latest_waiter = null;
}
}else{
int num_to_get = max_to_reserve>dont_wait?dont_wait:max_to_reserve;
dont_wait -= num_to_get;
total_reserve += num_to_get;
return( num_to_get );
}
}
}
public void
release()
{
try{
synchronized(this){
//System.out.println( name + "::release");
total_release++;
if ( waiting != 0 ){
waiting--;
notify();
}else{
dont_wait++;
}
}
}finally{
if ( DEBUG ){
debugExit();
}
}
}
public void
releaseAllWaiters()
{
synchronized(this){
int x = waiting;
for ( int i=0;i<x;i++ ){
release();
}
}
}
public void
releaseForever()
{
synchronized(this){
releaseAllWaiters();
released_forever = true;
}
}
public boolean
isReleasedForever()
{
synchronized(this){
return( released_forever );
}
}
public int
getValue()
{
synchronized(this){
return( dont_wait - waiting );
}
}
public String
getString()
{
synchronized(this){
return( "value=" + dont_wait + ",waiting=" + waiting + ",res=" + total_reserve + ",rel=" + total_release );
}
}
}