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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up with different versions on classes on the class path).

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/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2017 Red Hat, Inc., and individual contributors
 * as indicated by the @author tags.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.jboss.threads;

import java.util.AbstractQueue;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Queue;
import java.util.Arrays;
import java.util.ConcurrentModificationException;

import org.wildfly.common.Assert;

/**
 * A simple array-backed queue with a fixed size.
 */
public final class ArrayQueue extends AbstractQueue implements Queue {
    private final E[] elements;
    // elements are added at head
    private int head;
    // elements are removed at tail
    private int tail;
    private int modCnt;

    @SuppressWarnings({ "unchecked" })
    public ArrayQueue(final int capacity) {
        elements = (E[]) new Object[capacity];
    }

    public Iterator iterator() {
        return new Iterator() {
            private int pos = 0;
            private int size = size();
            private final int modIdx = modCnt;

            public boolean hasNext() {
                if (modCnt != modIdx) {
                    throw Messages.msg.concurrentModification();
                }
                return pos < size;
            }

            public E next() {
                if (modCnt != modIdx) {
                    throw Messages.msg.concurrentModification();
                }
                final int pos = this.pos;
                if (pos >= size) {
                    throw Messages.msg.noSuchElement();
                }
                final E[] elements = ArrayQueue.this.elements;
                final E value = elements[(tail + pos) % elements.length];
                this.pos = pos + 1;
                return value;
            }

            public void remove() {
                throw Assert.unsupported();
            }
        };
    }

    public boolean isEmpty() {
        return elements[tail] == null;
    }

    public int size() {
        final int head = this.head;
        final int tail = this.tail;
        final E[] elements = this.elements;
        if (elements[tail] == null) {
            return 0;
        } else if (head > tail) {
            return head - tail;
        } else {
            return head + elements.length - tail;
        }
    }

    public boolean offer(final E e) {
        Assert.checkNotNullParam("e", e);
        final int head = this.head;
        final E[] elements = this.elements;
        final int len = elements.length;
        if (elements[head] != null) {
            return false;
        } else {
            elements[head] = e;
            this.head = (head + 1) % len;
            modCnt++;
            return true;
        }
    }

    public E poll() {
        final int tail = this.tail;
        final E[] elements = this.elements;
        final E value = elements[tail];
        if (value != null) {
            modCnt++;
            elements[tail] = null;
            this.tail = (tail + 1) % elements.length;
        }
        return value;
    }

    public E peek() {
        final int tail = this.tail;
        return tail == -1 ? null : elements[tail];
    }

    public void clear() {
        Arrays.fill(elements, null);
        modCnt++;
        tail = head = 0;
    }
}