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  package org.apache.cayenne.crypto.unit;
  
  import java.security.Key;
  
  import org.apache.cayenne.crypto.transformer.bytes.BytesDecryptor;
  import org.apache.cayenne.crypto.transformer.bytes.BytesEncryptor;
  
  /**
   * A fake "cipher" used for unit tests that does simple bytes swapping.
   */
  public class SwapBytesTransformer implements BytesEncryptor, BytesDecryptor {
  
      private static final SwapBytesTransformer instance = new SwapBytesTransformer();
  
      public static BytesEncryptor encryptor() {
          return instance;
      }
  
      public static BytesDecryptor decryptor() {
          return instance;
      }
  
      private SwapBytesTransformer() {
      }
  
      @Override
      public byte[] decrypt(byte[] input, int inputOffset, Key key) {
  
          byte[] output = new byte[input.length - inputOffset];
          System.arraycopy(input, inputOffset, output, 0, input.length - inputOffset);
  
          swap(output, 0, output.length - 1);
          return output;
      }
  
      @Override
      public byte[] encrypt(byte[] input, int outputOffset, byte[] flags) {
  
          byte[] output = new byte[input.length + outputOffset];
  
          System.arraycopy(input, 0, output, outputOffset, input.length);
  
          swap(output, outputOffset, outputOffset + input.length - 1);
  
          return output;
      }
  
      private void swap(byte[] buffer, int start, int end) {
  
          if (start >= end) {
              return;
          }
  
          byte b = buffer[end];
          buffer[end] = buffer[start];
          buffer[start] = b;
  
          swap(buffer, ++start, --end);
      }
  }
  