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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;
      }
  }
  