io.questdb.std.AbstractLockable Maven / Gradle / Ivy
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* Copyright (c) 2014-2019 Appsicle
* Copyright (c) 2019-2020 QuestDB
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* Licensed under the Apache License, Version 2.0 (the "License");
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* http://www.apache.org/licenses/LICENSE-2.0
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package io.questdb.std;
public abstract class AbstractLockable {
private static final long TARGET_SEQUENCE_OFFSET;
@SuppressWarnings({"FieldCanBeLocal", "unused"})
// to "lock" the entry thread must successfully CAS targetSequence form "srcSequence" value
// to "srcSequence+1". Executing thread must not be changing value of "srcSequence"
private int tgtSequence;
private int srcSequence;
public boolean tryLock() {
return Unsafe.cas(this, TARGET_SEQUENCE_OFFSET, srcSequence, srcSequence + 1);
}
protected void of(int initialSequence) {
this.tgtSequence = initialSequence;
this.srcSequence = initialSequence;
}
static {
TARGET_SEQUENCE_OFFSET = Unsafe.getFieldOffset(AbstractLockable.class, "tgtSequence");
}
}