/* Copyright (C) 2001-2006 Artifex Software, Inc.
   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 that
   license.  Refer to licensing information at http://www.artifex.com/
   or contact Artifex Software, Inc.,  7 Mt. Lassen Drive - Suite A-134,
   San Rafael, CA  94903, U.S.A., +1(415)492-9861, for further information.
*/

/* $Id: idsdata.h 8022 2007-06-05 22:23:38Z giles $ */
/* Generic dictionary stack structure definition */

#ifndef idsdata_INCLUDED
#  define idsdata_INCLUDED

#include "isdata.h"

/* Define the dictionary stack structure. */
#ifndef dict_stack_DEFINED
#  define dict_stack_DEFINED
typedef struct dict_stack_s dict_stack_t;
#endif
struct dict_stack_s {

    ref_stack_t stack;		/* the actual stack of dictionaries */

/*
 * Switching between Level 1 and Level 2 involves inserting and removing
 * globaldict on the dictionary stack.  Instead of truly inserting and
 * removing entries, we replace globaldict by a copy of systemdict in
 * Level 1 mode.  min_dstack_size, the minimum number of entries, does not
 * change depending on language level; the countdictstack and dictstack
 * operators must take this into account.
 */
    uint min_size;		/* size of stack after clearing */

    int userdict_index;		/* index of userdict on stack */

/*
 * Cache a value for fast checking of def operations.
 * If the top entry on the dictionary stack is a writable dictionary,
 * dsspace is the space of the dictionary; if it is a non-writable
 * dictionary, dsspace = -1.  Then def is legal precisely if
 * r_space(pvalue) <= dsspace.  Note that in order for this trick to work,
 * the result of r_space must be a signed integer; some compilers treat
 * enums as unsigned, probably in violation of the ANSI standard.
 */
    int def_space;

/*
 * Cache values for fast name lookup.  If the top entry on the dictionary
 * stack is a readable dictionary with packed keys, dtop_keys, dtop_npairs,
 * and dtop_values are keys.value.packed, npairs, and values.value.refs
 * for that dictionary; otherwise, these variables point to a dummy
 * empty dictionary.
 */
    const ref_packed *top_keys;
    uint top_npairs;
    ref *top_values;

/*
 * Cache a copy of the bottom entry on the stack, which is never deleted.
 */
    ref system_dict;

};

/*
 * The top-entry pointers are recomputed after garbage collection, so we
 * don't declare them as pointers.
 */
#define public_st_dict_stack()	/* in interp.c */\
  gs_public_st_suffix_add0(st_dict_stack, dict_stack_t, "dict_stack_t",\
    dict_stack_enum_ptrs, dict_stack_reloc_ptrs, st_ref_stack)
#define st_dict_stack_num_ptrs st_ref_stack_num_ptrs

#endif /* idsdata_INCLUDED */
