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  package org.apache.cayenne.crypto.transformer.bytes;
  
  import java.security.Key;
  
  import org.apache.cayenne.crypto.key.KeySource;
  
  /**
   * @since 4.0
   */
  class HeaderDecryptor implements BytesDecryptor {
  
      private KeySource keySource;
      private BytesDecryptor delegate;
      private BytesDecryptor decompressDelegate;
  
      HeaderDecryptor(BytesDecryptor delegate, BytesDecryptor decompressDelegate, KeySource keySource) {
          this.delegate = delegate;
          this.keySource = keySource;
          this.decompressDelegate = decompressDelegate;
      }
  
      @Override
      public byte[] decrypt(byte[] input, int inputOffset, Key key) {
  
          Header header = Header.create(input, inputOffset);
  
          // ignoring the parameter key... using the key from the first block
          Key inRecordKey = keySource.getKey(header.getKeyName());
  
          // if compression was used to create a record, filter through GzipDecryptor...
          BytesDecryptor worker = header.isCompressed() ? decompressDelegate : delegate;
          // if record has HMAC, create appropriate decryptor
          if(header.haveHMAC()) {
              worker = new HmacDecryptor(worker, header, inRecordKey);
          }
  
          return worker.decrypt(input, inputOffset + header.size(), inRecordKey);
      }
  }
  