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Copy pathP1C1QueueStep6.java
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255 lines (210 loc) · 6.58 KB
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/**
*
* 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 javaopt.queue;
import static javaopt.queue.UnsafeDirectByteBuffer.CACHE_LINE_SIZE;
import static javaopt.queue.UnsafeDirectByteBuffer.alignedSlice;
import static javaopt.queue.UnsafeDirectByteBuffer.allocateAlignedByteBuffer;
import java.nio.ByteBuffer;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Queue;
import java.util.concurrent.locks.LockSupport;
public final class P1C1QueueStep6 implements Queue<Integer> {
public final static byte PRODUCER = 1;
public final static byte CONSUMER = 2;
// 24b,8b,32b | 24b,8b,32b | 24b,8b,32b | 24b,8b,32b
private final ByteBuffer buffy;
private final long headAddress;
private final long tailCacheAddress;
private final long tailAddress;
private final long headCacheAddress;
private final int capacity;
private final int mask;
private final long arrayBase;
private static final int INT_ELEMENT_SCALE = 2;
public P1C1QueueStep6(final int capacity) {
this(allocateAlignedByteBuffer(4 * CACHE_LINE_SIZE
+ findNextPositivePowerOfTwo(capacity) << INT_ELEMENT_SCALE,
CACHE_LINE_SIZE), findNextPositivePowerOfTwo(capacity),
(byte) (PRODUCER | CONSUMER));
}
/**
* This is to be used for an IPC queue with the direct buffer used being a
* memory mapped file.
*
* @param buff
* @param capacity
* @param viewMask
*/
public P1C1QueueStep6(final ByteBuffer buff, final int capacity, byte viewMask) {
this.capacity = findNextPositivePowerOfTwo(capacity);
buffy =
alignedSlice(4 * CACHE_LINE_SIZE + this.capacity << INT_ELEMENT_SCALE,
CACHE_LINE_SIZE, buff);
long alignedAddress = UnsafeDirectByteBuffer.getAddress(buffy);
headAddress = alignedAddress + (CACHE_LINE_SIZE / 2 - 8);
tailCacheAddress = headAddress + CACHE_LINE_SIZE;
tailAddress = tailCacheAddress + CACHE_LINE_SIZE;
headCacheAddress = tailAddress + CACHE_LINE_SIZE;
arrayBase = alignedAddress + 4 * CACHE_LINE_SIZE;
// producer owns tail and headCache
if ((viewMask & PRODUCER) == PRODUCER) {
setHeadCache(0);
setTail(0);
}
// consumer owns head and tailCache
if ((viewMask & CONSUMER) == CONSUMER) {
setTailCache(0);
setHead(0);
}
mask = this.capacity - 1;
}
public static int findNextPositivePowerOfTwo(final int value) {
return 1 << (32 - Integer.numberOfLeadingZeros(value - 1));
}
public boolean add(final Integer e) {
if (offer(e)) {
return true;
}
throw new IllegalStateException("Queue is full");
}
public boolean offer(final Integer e) {
if (null == e) {
throw new NullPointerException("Null is not a valid element");
}
while(true) {
final long currentTail = getTail();
final long wrapPoint = currentTail - capacity;
if (getHeadCache() <= wrapPoint) {
setHeadCache(getHead());
if (getHeadCache() <= wrapPoint) {
LockSupport.parkNanos(1L);
continue;
}
}
long offset = arrayBase
+ ((currentTail & mask) << INT_ELEMENT_SCALE);
UnsafeAccess.unsafe.putInt(offset, e.intValue());
setTail(currentTail + 1);
return true;
}
}
public Integer poll() {
while (true) {
final long currentHead = getHead();
if (currentHead >= getTailCache()) {
setTailCache(getTail());
if (currentHead >= getTailCache()) {
LockSupport.parkNanos(1L);
continue;
}
}
final long offset =
arrayBase + ((currentHead & mask) << INT_ELEMENT_SCALE);
final int e = UnsafeAccess.unsafe.getInt(offset);
setHead(currentHead + 1);
return e;
}
}
public Integer remove() {
final Integer e = poll();
if (null == e) {
throw new NoSuchElementException("Queue is empty");
}
return e;
}
public Integer element() {
final Integer e = peek();
if (null == e) {
throw new NoSuchElementException("Queue is empty");
}
return e;
}
public Integer peek() {
return null;
}
public int size() {
return (int) (getTail() - getHead());
}
public boolean isEmpty() {
return getTail() == getHead();
}
public boolean contains(final Object o) {
return false;
}
public Iterator<Integer> iterator() {
throw new UnsupportedOperationException();
}
public Object[] toArray() {
throw new UnsupportedOperationException();
}
public <T> T[] toArray(final T[] a) {
throw new UnsupportedOperationException();
}
public boolean remove(final Object o) {
throw new UnsupportedOperationException();
}
public boolean containsAll(final Collection<?> c) {
for (final Object o : c) {
if (!contains(o)) {
return false;
}
}
return true;
}
public boolean addAll(final Collection<? extends Integer> c) {
for (final Integer e : c) {
add(e);
}
return true;
}
public boolean removeAll(final Collection<?> c) {
throw new UnsupportedOperationException();
}
public boolean retainAll(final Collection<?> c) {
throw new UnsupportedOperationException();
}
public void clear() {
Object value;
do {
value = poll();
} while (null != value);
}
private long getHead() {
return UnsafeAccess.unsafe.getLongVolatile(null, headAddress);
}
private void setHead(final long value) {
UnsafeAccess.unsafe.putOrderedLong(null, headAddress, value);
}
private long getTail() {
return UnsafeAccess.unsafe.getLongVolatile(null, tailAddress);
}
private void setTail(final long value) {
UnsafeAccess.unsafe.putOrderedLong(null, tailAddress, value);
}
private long getHeadCache() {
return UnsafeAccess.unsafe.getLong(null, headCacheAddress);
}
private void setHeadCache(final long value) {
UnsafeAccess.unsafe.putLong(headCacheAddress, value);
}
private long getTailCache() {
return UnsafeAccess.unsafe.getLong(null, tailCacheAddress);
}
private void setTailCache(final long value) {
UnsafeAccess.unsafe.putLong(tailCacheAddress, value);
}
}