/* Copyright (C) 2001 Artifex Software, Inc.  All rights reserved.
  
  This file is part of GNU ghostscript

  GNU ghostscript is free software; you can redistribute it and/or modify it under
  the terms of the GNU General Public License as published by the Free Software
  Foundation; either version 2, or (at your option) any later version.

  GNU ghostscript is distributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

  You should have received a copy of the GNU General Public License along with
  ghostscript; see the file COPYING. If not, write to the Free Software Foundation,
  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

  
*/

/* $Id: zfarc4.c,v 1.4 2005/12/13 16:57:28 jemarch Exp $ */

/* this is the ps interpreter interface to the arcfour cipher filter
   used in PDF encryption. We provide both Decode and Encode filters;
   the cipher is symmetric, so the call to the underlying routines is
   identical between the two filters */

#include "memory_.h"
#include "ghost.h"
#include "oper.h"
#include "gsstruct.h"
#include "ialloc.h"
#include "idict.h"
#include "stream.h"
#include "strimpl.h"
#include "ifilter.h"
#include "sarc4.h"

/* <source> <dict> arcfour/filter <file> */

private int
z_arcfour_d(i_ctx_t * i_ctx_p)
{
    os_ptr op = osp;		/* i_ctx_p->op_stack.stack.p defined in osstack.h */
    ref *sop = NULL;
    stream_arcfour_state state;

    /* extract the key from the parameter dictionary */
    check_type(*op, t_dictionary);
    check_dict_read(*op);
    if (dict_find_string(op, "Key", &sop) <= 0)
	return_error(e_rangecheck);

    s_arcfour_set_key(&state, sop->value.const_bytes, r_size(sop));

    /* we pass npop=0, since we've no arguments left to consume */
    /* we pass 0 instead of the usual rspace(sop) will allocate storage for 
       filter state from the same memory pool as the stream it's coding. this
       causes no trouble because we maintain no pointers */
    return filter_read(i_ctx_p, 0, &s_arcfour_template,
		       (stream_state *) & state, 0);
}

/* encode version of the filter */
private int
z_arcfour_e(i_ctx_t * i_ctx_p)
{
    os_ptr op = osp;		/* i_ctx_p->op_stack.stack.p defined in osstack.h */
    ref *sop = NULL;
    stream_arcfour_state state;

    /* extract the key from the parameter dictionary */
    check_type(*op, t_dictionary);
    check_dict_read(*op);
    if (dict_find_string(op, "Key", &sop) <= 0)
	return_error(e_rangecheck);

    s_arcfour_set_key(&state, sop->value.const_bytes, r_size(sop));

    /* we pass npop=0, since we've no arguments left to consume */
    /* we pass 0 instead of the usual rspace(sop) will allocate storage for 
       filter state from the same memory pool as the stream it's coding. this
       causes no trouble because we maintain no pointers */
    return filter_write(i_ctx_p, 0, &s_arcfour_template,
			(stream_state *) & state, 0);
}

/* match the above routines to their postscript filter names
   this is how our 'private' routines get called externally */
const op_def zfarc4_op_defs[] = {
    op_def_begin_filter(),
    {"2ArcfourDecode", z_arcfour_d},
    {"2ArcfourEncode", z_arcfour_e},
    op_def_end(0)
};
