/*
* 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 com.facebook.presto.execution.buffer;
import javax.annotation.concurrent.ThreadSafe;
import java.util.concurrent.atomic.AtomicInteger;
import static com.google.common.base.MoreObjects.toStringHelper;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkState;
import static java.util.Objects.requireNonNull;
@ThreadSafe
class SerializedPageReference
{
private final SerializedPage serializedPage;
private final AtomicInteger referenceCount;
private final Runnable onDereference;
public SerializedPageReference(SerializedPage serializedPage, int referenceCount, Runnable onDereference)
{
this.serializedPage = requireNonNull(serializedPage, "page is null");
checkArgument(referenceCount > 0, "referenceCount must be at least 1");
this.referenceCount = new AtomicInteger(referenceCount);
this.onDereference = requireNonNull(onDereference, "onDereference is null");
}
public void addReference()
{
int oldReferences = referenceCount.getAndIncrement();
checkState(oldReferences > 0, "Page has already been dereferenced");
}
public SerializedPage getSerializedPage()
{
return serializedPage;
}
public int getPositionCount()
{
return serializedPage.getPositionCount();
}
public long getRetainedSizeInBytes()
{
return serializedPage.getRetainedSizeInBytes();
}
public void dereferencePage()
{
int remainingReferences = referenceCount.decrementAndGet();
checkState(remainingReferences >= 0, "Page reference count is negative");
if (remainingReferences == 0) {
onDereference.run();
}
}
@Override
public String toString()
{
return toStringHelper(this)
.add("referenceCount", referenceCount)
.toString();
}
}