/*
* 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.operator.exchange;
import com.facebook.presto.spi.Page;
import javax.annotation.concurrent.ThreadSafe;
import java.util.concurrent.atomic.AtomicInteger;
import static com.google.common.base.Preconditions.checkArgument;
import static java.util.Objects.requireNonNull;
@ThreadSafe
class PageReference
{
private final Page page;
private final Runnable onFree;
private final AtomicInteger referenceCount;
public PageReference(Page page, int referenceCount, Runnable onFree)
{
this.page = requireNonNull(page, "page is null");
this.onFree = requireNonNull(onFree, "onFree is null");
checkArgument(referenceCount >= 1, "referenceCount must be at least 1");
this.referenceCount = new AtomicInteger(referenceCount);
}
public long getRetainedSizeInBytes()
{
return page.getRetainedSizeInBytes();
}
public Page removePage()
{
int referenceCount = this.referenceCount.decrementAndGet();
checkArgument(referenceCount >= 0, "Page reference count is negative");
if (referenceCount == 0) {
onFree.run();
}
return page;
}
}