/* 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: iesdata.h 9043 2008-08-28 22:48:19Z giles $ */
/* Generic execution stack structure definition */

#ifndef iesdata_INCLUDED
#  define iesdata_INCLUDED

#include "isdata.h"

/* Define the execution stack structure. */
typedef struct exec_stack_s {

    ref_stack_t stack;		/* the actual execution stack */

/*
 * To improve performance, we cache the currentfile pointer
 * (i.e., `shallow-bind' it in Lisp terminology).  The invariant is as
 * follows: either esfile points to the currentfile slot on the estack
 * (i.e., the topmost slot with an executable file), or it is 0.
 * To maintain the invariant, it is sufficient that whenever a routine
 * pushes or pops anything on the estack, if the object *might* be
 * an executable file, invoke esfile_clear_cache(); alternatively,
 * immediately after pushing an object, invoke esfile_check_cache().
 */
    ref *current_file;

} exec_stack_t;

/*
 * current_file is cleared by garbage collection, so we don't declare it
 * as a pointer.
 */
#define public_st_exec_stack()	/* in interp.c */\
  gs_public_st_suffix_add0(st_exec_stack, exec_stack_t, "exec_stack_t",\
    exec_stack_enum_ptrs, exec_stack_reloc_ptrs, st_ref_stack)
#define st_exec_stack_num_ptrs st_ref_stack_num_ptrs

#endif /* iesdata_INCLUDED */
