com.amazonaws.services.glacier.internal.TreeHashInputStream Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of aws-java-sdk Show documentation

The Amazon Web Services 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).

The newest version!

/*
 * Copyright 2012-2014 Amazon Technologies, Inc.
 *
 * 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://aws.amazon.com/apache2.0
 *
 * 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.services.glacier.internal;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import com.amazonaws.services.glacier.TreeHashGenerator;

/**
 * Filter input stream that enables tree hash computation on the bytes that
 * it streams.
 */
public class TreeHashInputStream extends FilterInputStream {

    public TreeHashInputStream(InputStream in) throws NoSuchAlgorithmException {
        super(new DigestInputStream(in, MessageDigest.getInstance("SHA-256")));
        this.digestInputStream = (DigestInputStream) super.in;
    }

    /**
     * The private DigestInputStream we use to wrap the source input stream and
     * compute a client-side checksum for every part of the message.
     */
    private final DigestInputStream digestInputStream;

    /**
     * The checksums of megabyte-sized parts of the bytes streamed.
     */
    private final List checksums = new ArrayList();

    private boolean closed = false;

    /**
     * Returns the list of one-megabyte checksums for this input stream. Only
     * valid once the stream has been closed.
     *
     * @throws IOException
     *             If the stream hasn't been closed.
     */
    public List getChecksums() throws IOException {
        if ( !closed ) {
            throw new IOException("Stream must be closed before getting checksums");
        }
        return Collections.unmodifiableList(checksums);
    }

    public String getTreeHash() throws IOException {
        if ( !closed ) {
            throw new IOException("Stream must be closed before getting the tree hash");
        }
        return TreeHashGenerator.calculateTreeHash(getChecksums());
    }

    private int byteOffset = 0;
    private static final int MB = 1024 * 1024;

    @Override
    public int read() throws IOException {
        int read = super.read();
        if ( read >= 0 )
            byteOffset++;

        digestPart();
        return read;
    }

    @Override
    public int read(byte[] b, int off, int len) throws IOException {
        int totalBytesRead = 0;
        int lastBytesRead = 0;
        while ( totalBytesRead < len && lastBytesRead > -1 ) {
            int bytesToRead = Math.min(MB - byteOffset, len - totalBytesRead);

            lastBytesRead = super.read(b, off + totalBytesRead, bytesToRead);
            if ( lastBytesRead > 0 ) {
                totalBytesRead += lastBytesRead;
                byteOffset += lastBytesRead;
            }

            digestPart();
            
            if (lastBytesRead == -1 && totalBytesRead == 0) return -1;
        }

        return totalBytesRead;
    }

    /**
     * Digests the current part of the message, if necessary, and resets digest
     * state.
     */
    private void digestPart() {
        if ( byteOffset >= MB ) {
            byteOffset = 0;
            checksums.add(digestInputStream.getMessageDigest().digest());
            digestInputStream.getMessageDigest().reset();
        }
    }

    @Override
    public void close() throws IOException {
        super.close();

        closed = true;
        if ( byteOffset > 0 ) {
            checksums.add(digestInputStream.getMessageDigest().digest());
        }
    }
}