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/*******************************************************************************
* Copyright (c) 1997, 2008 by ProSyst Software GmbH
* http://www.prosyst.com
*
* This program and the accompanying materials
* are made available under the terms of the Eclipse Public License 2.0
* which accompanies this distribution, and is available at
* https://www.eclipse.org/legal/epl-2.0/
*
* SPDX-License-Identifier: EPL-2.0
*
* Contributors:
* ProSyst Software GmbH - initial API and implementation
*******************************************************************************/
package org.eclipse.equinox.internal.util.impl.tpt.timer;
/**
* @author Pavlin Dobrev
* @version 1.0
*/
class TimerQueue {
static final int POOL_SIZE = 20;
QueueElement[] pool = new QueueElement[POOL_SIZE];
int filled = 0;
QueueElement first;
QueueElement lastInserted;
TimerQueue() {
}
/**
* Adds a new task to the priority queue.
*/
void add(TimerQueueNode task) {
QueueElement toAdd = getQueueElement();
toAdd.node = task;
if (first == null) {
first = toAdd;
} else {
insertElement(toAdd);
}
}
/**
* Return the "head task" of the priority queue. (The head task is an task
* with the lowest nextExecutionTime.)
*/
TimerQueueNode getMin() {
return (first != null) ? first.node : null;
}
/**
* Remove the head task from the priority queue.
*/
void removeMin() {
if (first != null) {
if (lastInserted == first) {
lastInserted = null;
}
if (filled < POOL_SIZE) {
QueueElement toFree = first;
first = first.next;
freeQueueElement(toFree);
} else {
first = first.next;
}
}
}
/**
* Sets the nextExecutionTime associated with the head task to the specified
* value, and adjusts priority queue accordingly.
*/
void rescheduleMin(long newTime) {
first.node.runOn = newTime;
if (first.next != null) {
if (lastInserted == first) {
lastInserted = null;
}
QueueElement el = first;
first = first.next;
el.next = null;
insertElement(el);
}
}
/**
* Returns true if the priority queue contains no elements.
*/
boolean isEmpty() {
return first == null;
}
/**
* Removes all elements from the priority queue.
*/
void clear() {
while (first != null) {
first.node.returnInPool();
first = first.next;
}
lastInserted = null;
}
void insertElement(QueueElement newElement) {
if (first.node.runOn >= newElement.node.runOn) {
/* private case - insert in the beginning of the queue */
newElement.next = first;
first = newElement;
} else if (lastInserted != null) {
if (lastInserted.node.runOn == newElement.node.runOn) {
QueueElement tmp = lastInserted.next;
lastInserted.next = newElement;
newElement.next = tmp;
} else if (lastInserted.node.runOn > newElement.node.runOn) {
// System.out.println("insert 1");
doInsertElement(first, newElement);
} else {
// System.out.println("insert 2");
doInsertElement(lastInserted, newElement);
}
} else {
// System.out.println("insert 3");
doInsertElement(first, newElement);
}
}
/**
* elToInsert should not be placed before firstEl, because firstEl may not
* be the first element of the queue
*/
void doInsertElement(QueueElement firstEl, QueueElement elToInsert) {
QueueElement tmp = firstEl;
QueueElement prev = firstEl;
while (tmp != null && tmp.node.runOn < elToInsert.node.runOn) {
prev = tmp;
tmp = tmp.next;
}
if (tmp == null) {
/* reached the end of the queue */
prev.next = elToInsert;
} else {
prev.next = elToInsert;
elToInsert.next = tmp;
}
lastInserted = elToInsert;
}
void removeTimerNode(TimerQueueNode node) {
QueueElement tmp = first;
QueueElement prev = null;
while (tmp != null) {
if (node.listener == tmp.node.listener && node.event == tmp.node.event) {
if (prev != null) {
if (lastInserted == tmp) {
lastInserted = prev;
}
prev.next = tmp.next;
if (filled < POOL_SIZE) {
freeQueueElement(tmp);
}
} else {
/* removing the first element */
if (lastInserted == first) {
lastInserted = null;
}
if (filled < POOL_SIZE) {
QueueElement toFree = first;
first = first.next;
freeQueueElement(toFree);
} else {
first = first.next;
}
}
break;
}
prev = tmp;
tmp = tmp.next;
}
}
private QueueElement getQueueElement() {
return (filled > 0) ? pool[--filled] : new QueueElement();
}
private void freeQueueElement(QueueElement toFree) {
if (filled < POOL_SIZE) {
pool[filled] = toFree;
filled++;
toFree.next = null;
toFree.node = null;
}
}
private class QueueElement {
QueueElement next;
TimerQueueNode node;
public QueueElement() {
}
}
}
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