org.jclouds.glacier.util.TreeHash.java Source code

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Here is the source code for org.jclouds.glacier.util.TreeHash.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.glacier.util;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static org.jclouds.util.Closeables2.closeQuietly;

import java.io.IOException;
import java.io.InputStream;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;

import org.jclouds.io.Payload;

import com.google.common.base.Objects;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableList.Builder;
import com.google.common.collect.ImmutableSortedMap;
import com.google.common.hash.HashCode;
import com.google.common.hash.Hashing;
import com.google.common.hash.HashingInputStream;
import com.google.common.io.ByteStreams;

public final class TreeHash {
    private static final int CHUNK_SIZE = 1024 * 1024;

    private final HashCode treeHash;
    private final HashCode linearHash;

    private TreeHash(HashCode treeHash, HashCode linearHash) {
        this.treeHash = checkNotNull(treeHash, "treeHash");
        this.linearHash = checkNotNull(linearHash, "linearHash");
    }

    public HashCode getLinearHash() {
        return linearHash;
    }

    public HashCode getTreeHash() {
        return treeHash;
    }

    @Override
    public int hashCode() {
        return Objects.hashCode(this.treeHash, this.linearHash);
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        TreeHash other = (TreeHash) obj;
        return Objects.equal(this.treeHash, other.treeHash) && Objects.equal(this.linearHash, other.linearHash);
    }

    @Override
    public String toString() {
        return "TreeHash [treeHash=" + treeHash + ", linearHash=" + linearHash + "]";
    }

    private static HashCode hashList(Collection<HashCode> hashList) {
        Builder<HashCode> result = ImmutableList.builder();
        while (hashList.size() > 1) {
            //Hash pairs of values and add them to the result list.
            for (Iterator<HashCode> it = hashList.iterator(); it.hasNext();) {
                HashCode hc1 = it.next();
                if (it.hasNext()) {
                    HashCode hc2 = it.next();
                    result.add(Hashing.sha256().newHasher().putBytes(hc1.asBytes()).putBytes(hc2.asBytes()).hash());
                } else {
                    result.add(hc1);
                }
            }
            hashList = result.build();
            result = ImmutableList.builder();
        }
        return hashList.iterator().next();
    }

    /**
     * Builds the Hash and the TreeHash values of the payload.
     *
     * @return The calculated TreeHash.
     * @see <a href="http://docs.aws.amazon.com/amazonglacier/latest/dev/checksum-calculations.html" />
     */
    public static TreeHash buildTreeHashFromPayload(Payload payload) throws IOException {
        InputStream is = null;
        try {
            is = checkNotNull(payload, "payload").openStream();
            Builder<HashCode> list = ImmutableList.builder();
            HashingInputStream linearHis = new HashingInputStream(Hashing.sha256(), is);
            while (true) {
                HashingInputStream chunkedHis = new HashingInputStream(Hashing.sha256(),
                        ByteStreams.limit(linearHis, CHUNK_SIZE));
                long count = ByteStreams.copy(chunkedHis, ByteStreams.nullOutputStream());
                if (count == 0) {
                    break;
                }
                list.add(chunkedHis.hash());
            }
            //The result list contains exactly one element now.
            return new TreeHash(hashList(list.build()), linearHis.hash());
        } finally {
            closeQuietly(is);
        }
    }

    /**
     * Builds a TreeHash based on a map of hashed chunks.
     *
     * @return The calculated TreeHash.
     * @see <a href="http://docs.aws.amazon.com/amazonglacier/latest/dev/checksum-calculations.html" />
     */
    public static HashCode buildTreeHashFromMap(Map<Integer, HashCode> map) {
        checkArgument(!map.isEmpty(), "The map cannot be empty.");
        return hashList(ImmutableSortedMap.copyOf(map).values());
    }
}