/* Copyright (C) 1990, 1992, 1997 Aladdin Enterprises.  All rights reserved.
  
  This software is provided AS-IS with no warranty, either express or
  implied.
  
  This software is distributed under license and may not be copied,
  modified or distributed except as expressly authorized under the terms
  of the license contained in the file LICENSE in this distribution.
  
  For more information about licensing, please refer to
  http://www.ghostscript.com/licensing/. For information on
  commercial licensing, go to http://www.artifex.com/licensing/ or
  contact Artifex Software, Inc., 101 Lucas Valley Road #110,
  San Rafael, CA  94903, U.S.A., +1(415)492-9861.
*/

/* $Id: gscrypt1.h,v 1.5 2002/06/16 08:45:42 lpd Exp $ */
/* Interface to Adobe Type 1 encryption/decryption. */

#ifndef gscrypt1_INCLUDED
#  define gscrypt1_INCLUDED

/* Normal public interface */
typedef ushort crypt_state;
int gs_type1_encrypt(byte * dest, const byte * src, uint len,
		     crypt_state * pstate);
int gs_type1_decrypt(byte * dest, const byte * src, uint len,
		     crypt_state * pstate);

/* Define the encryption parameters and procedures. */
#define crypt_c1 ((ushort)52845)
#define crypt_c2 ((ushort)22719)
/* c1 * c1' == 1 mod 2^16. */
#define crypt_c1_inverse ((ushort)27493)
#define encrypt_next(ch, state, chvar)\
  (chvar = ((ch) ^ (state >> 8)),\
   state = (chvar + state) * crypt_c1 + crypt_c2)
#define decrypt_this(ch, state)\
  ((ch) ^ (state >> 8))
#define decrypt_next(ch, state, chvar)\
  (chvar = decrypt_this(ch, state),\
   decrypt_skip_next(ch, state))
#define decrypt_skip_next(ch, state)\
  (state = ((ch) + state) * crypt_c1 + crypt_c2)
#define decrypt_skip_previous(ch, state)\
  (state = (state - crypt_c2) * crypt_c1_inverse - (ch))

#endif /* gscrypt1_INCLUDED */
