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/*
* Copyright (C) 2016 The Android Open Source Project
*
* 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.android.apkzlib.zip;
import com.android.apkzlib.zip.utils.CloseableByteSource;
import com.google.common.hash.HashCode;
import com.google.common.hash.HashFunction;
import com.google.common.io.ByteProcessor;
import com.google.common.io.ByteSink;
import com.google.common.io.ByteSource;
import com.google.common.io.CharSource;
import com.google.common.util.concurrent.ListenableFuture;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.charset.Charset;
import java.util.concurrent.ExecutionException;
import javax.annotation.Nonnull;
/**
* {@code ByteSource} that delegates all operations to another {@code ByteSource}. The other
* byte source, the <em>delegate</em>, may be computed lazily.
*/
public class LazyDelegateByteSource extends CloseableByteSource {
/**
* Byte source where we delegate operations to.
*/
@Nonnull
private final ListenableFuture<CloseableByteSource> delegate;
/**
* Creates a new byte source that delegates operations to the provided source.
* @param delegate the source that will receive all operations
*/
public LazyDelegateByteSource(@Nonnull ListenableFuture<CloseableByteSource> delegate) {
this.delegate = delegate;
}
/**
* Obtains the delegate future.
* @return the delegate future, that may be computed or not
*/
@Nonnull
public ListenableFuture<CloseableByteSource> getDelegate() {
return delegate;
}
/**
* Obtains the byte source, waiting for the future to be computed.
* @return the byte source
* @throws IOException failed to compute the future :)
*/
@Nonnull
private CloseableByteSource get() throws IOException {
try {
CloseableByteSource r = delegate.get();
if (r == null) {
throw new IOException("Delegate byte source computation resulted in null.");
}
return r;
} catch (InterruptedException e) {
throw new IOException("Interrupted while waiting for byte source computation.", e);
} catch (ExecutionException e) {
throw new IOException("Failed to compute byte source.", e);
}
}
@Override
public CharSource asCharSource(Charset charset) {
try {
return get().asCharSource(charset);
} catch (IOException e) {
throw new RuntimeException(e);
}
}
@Override
public InputStream openBufferedStream() throws IOException {
return get().openBufferedStream();
}
@Override
public ByteSource slice(long offset, long length) {
try {
return get().slice(offset, length);
} catch (IOException e) {
throw new RuntimeException(e);
}
}
@Override
public boolean isEmpty() throws IOException {
return get().isEmpty();
}
@Override
public long size() throws IOException {
return get().size();
}
@Override
public long copyTo(@Nonnull OutputStream output) throws IOException {
return get().copyTo(output);
}
@Override
public long copyTo(@Nonnull ByteSink sink) throws IOException {
return get().copyTo(sink);
}
@Override
public byte[] read() throws IOException {
return get().read();
}
@Override
public <T> T read(@Nonnull ByteProcessor<T> processor) throws IOException {
return get().read(processor);
}
@Override
public HashCode hash(HashFunction hashFunction) throws IOException {
return get().hash(hashFunction);
}
@Override
public boolean contentEquals(@Nonnull ByteSource other) throws IOException {
return get().contentEquals(other);
}
@Override
public InputStream openStream() throws IOException {
return get().openStream();
}
@Override
public void innerClose() throws IOException {
get().close();
}
}
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