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LazyReadChannel.java
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LazyReadChannel.java
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/*
* Copyright 2022 Google LLC
*
* 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.google.cloud.storage;
import java.nio.channels.ReadableByteChannel;
import java.util.function.Supplier;
import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
import org.checkerframework.checker.nullness.qual.NonNull;
final class LazyReadChannel<RBC extends ReadableByteChannel, T> {
private final Supplier<ReadableByteChannelSession<RBC, T>> sessionSupplier;
@MonotonicNonNull private volatile ReadableByteChannelSession<RBC, T> session;
@MonotonicNonNull private volatile RBC channel;
private boolean open = false;
LazyReadChannel(Supplier<ReadableByteChannelSession<RBC, T>> sessionSupplier) {
this.sessionSupplier = sessionSupplier;
}
@NonNull
RBC getChannel() {
if (channel != null) {
return channel;
} else {
synchronized (this) {
if (channel == null) {
open = true;
channel = getSession().open();
}
return channel;
}
}
}
@NonNull
ReadableByteChannelSession<RBC, T> getSession() {
if (session != null) {
return session;
} else {
synchronized (this) {
if (session == null) {
session = sessionSupplier.get();
}
return session;
}
}
}
boolean isOpen() {
return open && getChannel().isOpen();
}
}