org.jclouds.examples.blobstore.hdfs.io.HdfsPayloadSlicer.java Source code

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Here is the source code for org.jclouds.examples.blobstore.hdfs.io.HdfsPayloadSlicer.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.jclouds.examples.blobstore.hdfs.io;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

import java.io.IOException;
import java.io.InputStream;

import javax.inject.Singleton;

import org.apache.hadoop.fs.FSDataInputStream;
import org.jclouds.examples.blobstore.hdfs.io.payloads.HdfsPayload;
import org.jclouds.io.Payload;
import org.jclouds.io.internal.BasePayloadSlicer;
import org.jclouds.io.payloads.InputStreamSupplierPayload;

import com.google.common.io.Closeables;
import com.google.common.io.InputSupplier;
import com.google.common.io.LimitInputStream;

@Singleton
public class HdfsPayloadSlicer extends BasePayloadSlicer {

    @Override
    public Payload slice(Payload input, long offset, long length) {
        checkNotNull(input);
        checkArgument(offset >= 0, "offset is negative");
        checkArgument(length >= 0, "length is negative");
        Payload returnVal;
        if (input instanceof HdfsPayload) {
            returnVal = doSlice((FSDataInputStream) ((HdfsPayload) input).getInput(), offset, length);
            return copyMetadataAndSetLength(input, returnVal, length);
        } else {
            return super.slice(input, offset, length);
        }
    }

    protected Payload doSlice(final FSDataInputStream inputStream, final long offset, final long length) {
        return new InputStreamSupplierPayload(new InputSupplier<InputStream>() {
            public InputStream getInput() throws IOException {
                if (offset > 0) {
                    try {
                        inputStream.seek(offset);
                    } catch (IOException e) {
                        Closeables.closeQuietly(inputStream);
                        throw e;
                    }
                }
                return new LimitInputStream(inputStream, length);
            }
        });
    }
}