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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 1.8 and up. The APIs are designed primarily to be used in conjunction with the BC LTS provider but may also be used with other providers providing cryptographic services.

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package org.bouncycastle.tsp.ers;

import java.util.HashMap;
import java.util.Map;

import org.bouncycastle.asn1.x509.AlgorithmIdentifier;
import org.bouncycastle.operator.DigestCalculator;
import org.bouncycastle.util.Arrays;

/**
 * An ERSData object that caches hash calculations.
 */
public abstract class ERSCachingData
    implements ERSData
{
    private Map preCalcs = new HashMap();

    /**
     * Generates a hash for the whole DataGroup.
     *
     * @param digestCalculator the {@link DigestCalculator} to use for computing the hash
     * @return a hash that is representative of the whole DataGroup
     */
    public byte[] getHash(DigestCalculator digestCalculator, byte[] previousChainHash)
    {
        CacheIndex digAlgID = new CacheIndex(digestCalculator.getAlgorithmIdentifier(), previousChainHash);
        if (preCalcs.containsKey(digAlgID))
        {
            return (byte[])preCalcs.get(digAlgID);
        }

        byte[] hash = calculateHash(digestCalculator, previousChainHash);

        preCalcs.put(digAlgID, hash);

        return hash;
    }

    protected abstract byte[] calculateHash(DigestCalculator digestCalculator, byte[] previousChainHash);

    private static class CacheIndex
    {
        final AlgorithmIdentifier algId;
        final byte[] chainHash;

        private CacheIndex(AlgorithmIdentifier algId, byte[] chainHash)
        {
            this.algId = algId;
            this.chainHash = chainHash;
        }

        public boolean equals(Object o)
        {
            if (this == o)
            {
                return true;
            }
            if (!(o instanceof CacheIndex))
            {
                return false;
            }
            CacheIndex that = (CacheIndex)o;
            return algId.equals(that.algId) && Arrays.areEqual(chainHash, that.chainHash);
        }

        public int hashCode()
        {
            int result = algId.hashCode();
            return 31 * result + Arrays.hashCode(chainHash);
        }
    }
}