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package org.apache.cayenne.crypto.transformer.bytes;

import java.security.Key;

/**
 * Encryptor that stores authentication code into output.
 * HMAC is formed from full header concatenated with unencrypted input.
 *
 * @since 4.0
 */
class HmacEncryptor extends HmacCreator implements BytesEncryptor {

    BytesEncryptor delegate;

    HmacEncryptor(BytesEncryptor delegate, Header header, Key key) {
        super(header, key);
        this.delegate = delegate;
    }

    @Override
    public byte[] encrypt(byte[] input, int outputOffset, byte[] flags) {
        byte[] hmac = createHmac(input);
        byte[] encrypted = delegate.encrypt(input, outputOffset + hmac.length + 1, flags);
        encrypted[outputOffset++] = (byte)hmac.length; // store HMAC length
        System.arraycopy(hmac, 0, encrypted, outputOffset, hmac.length);
        return encrypted;
    }
}
