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The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. This jar contains APIs for JDK 1.5 to JDK 1.8. The APIs can be used in conjunction with a JCE/JCA provider such as the one provided with the Bouncy Castle Cryptography APIs.

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package org.bouncycastle.tsp;

import java.io.IOException;
import java.io.OutputStream;

import org.bouncycastle.asn1.tsp.PartialHashtree;
import org.bouncycastle.operator.DigestCalculator;
import org.bouncycastle.util.Arrays;

public class PartialHashTreeProcessor
{
    private final byte[][] values;

    public PartialHashTreeProcessor(PartialHashtree tree)
    {
        this.values = tree.getValues();
    }

    /**
     * Compute a hash over the whole partialHashTree:
     * - Concatenate all the hashes contained in the partial hash tree;
     * - Generate a hash over the concatenated hashes, using a provided {@link DigestCalculator}.
     *
     * @param digestCalculator the {@link DigestCalculator} to use in order to generate the hash
     * @return a hash value that is representative of the whole partial hash tree.
     */
    public byte[] getHash(DigestCalculator digestCalculator)
    {
        if (values.length == 1)
        {
            return values[0];
        }

        try
        {
            OutputStream dOut = digestCalculator.getOutputStream();

            for (int i = 1; i != values.length; i++)
            {
                dOut.write(values[i]);
            }

            return digestCalculator.getDigest();
        }
        catch (IOException e)
        {
            throw new IllegalStateException("calculator failed: " + e.getMessage());
        }
    }

    /**
     * Checks whether a PartialHashtree (RFC4998) contains a given hash.
     *
     * @param hash            the hash to check
     * @throws PartialHashTreeVerificationException if the hash is not present in the
     * PartialHashtree
     */
    public void verifyContainsHash(final byte[] hash)
        throws PartialHashTreeVerificationException
    {
        if (!containsHash(hash))
        {
            throw new PartialHashTreeVerificationException("calculated hash is not present in " + "partial hash tree");
        }
    }

    /**
     * Checks whether a PartialHashtree (RFC4998) contains a given hash.
     *
     * @param hash            the hash to check
     * @return true if the hash is present within the PartialHashtree's set of values, false
     * otherwise.
     */
    public boolean containsHash(final byte[] hash)
    {
        for (int i = 1; i != values.length; i++)
        {
            if (Arrays.areEqual(hash, values[i]))
            {
                return true;
            }
        }

        return false;
    }
}