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Improvement: simplified AbstractConstant compareTo.

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Motivation:

AbstractConstant.compareTo seems complex and hard to understand. Also it allocates unnecessary 1 byte in direct buffer and holds unnecessary pointer to this byte butter.

Modifications:

uniquifier (id) variable now initialized during Constant creation and thus no need in volatile and no need in uniquifier() method as it could be easily replaced with AtomicLong.

Result:

Every Constant instance now consumes less bytes for pointer, don't consume anything in direct buffer.
This commit is contained in:
Dmitriy Dumanskiy 2016-08-03 00:24:45 +03:00 committed by Norman Maurer
parent 26aa34853a
commit a06afe8b77
1 changed files with 6 additions and 28 deletions
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34
common/src/main/java/io/netty/util/AbstractConstant.java
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@ -15,20 +15,17 @@
*/
package io.netty.util;
import io.netty.util.internal.PlatformDependent;
import io.netty.util.internal.ThreadLocalRandom;
import java.nio.ByteBuffer;
import java.util.concurrent.atomic.AtomicLong;
/**
* Base implementation of {@link Constant}.
*/
public abstract class AbstractConstant<T extends AbstractConstant<T>> implements Constant<T> {
private static final AtomicLong uniqueIdGenerator = new AtomicLong();
private final int id;
private final String name;
private volatile long uniquifier;
private ByteBuffer directBuffer;
private final long uniquifier;
/**
* Creates a new instance.
@ -36,6 +33,7 @@ public abstract class AbstractConstant<T extends AbstractConstant<T>> implements
protected AbstractConstant(int id, String name) {
this.id = id;
this.name = name;
this.uniquifier = uniqueIdGenerator.getAndIncrement();
}
@Override
@ -78,34 +76,14 @@ public abstract class AbstractConstant<T extends AbstractConstant<T>> implements
return returnCode;
}
long thisUV = uniquifier();
long otherUV = other.uniquifier();
if (thisUV < otherUV) {
if (uniquifier < other.uniquifier) {
return -1;
}
if (thisUV > otherUV) {
if (uniquifier > other.uniquifier) {
return 1;
}
throw new Error("failed to compare two different constants");
}
private long uniquifier() {
long uniquifier;
if ((uniquifier = this.uniquifier) == 0) {
synchronized (this) {
while ((uniquifier = this.uniquifier) == 0) {
if (PlatformDependent.hasUnsafe()) {
directBuffer = ByteBuffer.allocateDirect(1);
this.uniquifier = PlatformDependent.directBufferAddress(directBuffer);
} else {
directBuffer = null;
this.uniquifier = ThreadLocalRandom.current().nextLong();
}
}
}
}
return uniquifier;
}
}