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The AWS SDK for Java with support for OSGi. The AWS SDK for Java provides Java APIs for building software on AWS' cost-effective, scalable, and reliable infrastructure products. The AWS Java SDK allows developers to code against APIs for all of Amazon's infrastructure web services (Amazon S3, Amazon EC2, Amazon SQS, Amazon Relational Database Service, Amazon AutoScaling, etc).

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/*
 * Copyright 2014-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file 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.amazonaws.internal;

import static com.amazonaws.util.SdkRuntime.shouldAbort;

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

import org.apache.commons.logging.LogFactory;

import com.amazonaws.AbortedException;
import com.amazonaws.util.IOUtils;

/**
 * Base class for AWS Java SDK specific {@link InputStream}.
 */
public abstract class SdkInputStream extends InputStream implements
        MetricAware, Releasable {
    /**
     * Returns the underlying input stream, if any, from the subclass; or null
     * if there is no underlying input stream.
     */
    abstract protected InputStream getWrappedInputStream();

    @Override
    public final boolean isMetricActivated() {
        InputStream in = getWrappedInputStream();
        if (in instanceof MetricAware) {
            MetricAware metricAware = (MetricAware)in;
            return metricAware.isMetricActivated();
        }
        return false;
    }

    /**
     * Aborts with subclass specific abortion logic executed if needed.
     * Note the interrupted status of the thread is cleared by this method.
     * @throws AbortedException if found necessary.
     */
    protected final void abortIfNeeded() {
        if (shouldAbort()) {
            try {
                abort();    // execute subclass specific abortion logic
            } catch (IOException e) {
                LogFactory.getLog(getClass()).debug("FYI", e);
            }
            throw new AbortedException();
        }
    }

    /**
     * Can be used to provide abortion logic prior to throwing the
     * AbortedException. No-op by default.
     */
    protected void abort() throws IOException {
        // no-op by default, but subclass such as S3ObjectInputStream may override
    }

    /**
     * WARNING: Subclass that overrides this method must NOT call
     * super.release() or else it would lead to infinite loop.
     * 
     * {@inheritDoc}
     */
    @Override
    public void release() {
        // Don't call IOUtils.release(in, null) or else could lead to infinite loop
        IOUtils.closeQuietly(this, null);
        InputStream in = getWrappedInputStream();
        if (in instanceof Releasable) {
            // This allows any underlying stream that has the close operation
            // disabled to be truly released
            Releasable r = (Releasable)in;
            r.release();
        }
    }
}