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diff --git a/gs/src/estack.h b/gs/src/estack.h
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+/* Copyright (C) 1989, 1992, 1993, 1994, 1996, 1997 Aladdin Enterprises.  All rights reserved.
+  
+  This file is part of Aladdin Ghostscript.
+  
+  Aladdin Ghostscript is distributed with NO WARRANTY OF ANY KIND.  No author
+  or distributor accepts any responsibility for the consequences of using it,
+  or for whether it serves any particular purpose or works at all, unless he
+  or she says so in writing.  Refer to the Aladdin Ghostscript Free Public
+  License (the "License") for full details.
+  
+  Every copy of Aladdin Ghostscript must include a copy of the License,
+  normally in a plain ASCII text file named PUBLIC.  The License grants you
+  the right to copy, modify and redistribute Aladdin Ghostscript, but only
+  under certain conditions described in the License.  Among other things, the
+  License requires that the copyright notice and this notice be preserved on
+  all copies.
+*/
+
+/* estack.h */
+/* Definitions for the execution stack */
+#include "istack.h"
+
+/* Define the execution stack pointers. */
+typedef s_ptr es_ptr;
+typedef const_s_ptr const_es_ptr;
+extern ref_stack e_stack;
+#define esbot (e_stack.bot)
+#define esp (e_stack.p)
+#define estop (e_stack.top)
+
+/*
+ * 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().
+ */
+extern ref *esfile;
+#define esfile_clear_cache() (esfile = 0)
+#define esfile_set_cache(pref) (esfile = (pref))
+#define esfile_check_cache()\
+  if ( r_has_type_attrs(esp, t_file, a_executable) )\
+    esfile_set_cache(esp)
+
+/*
+ * The execution stack is used for three purposes:
+ *
+ *	- Procedures being executed are held here.  They always have
+ * type = t_array, t_mixedarray, or t_shortarray, with a_executable set.
+ * More specifically, the e-stack holds the as yet unexecuted tail of the
+ * procedure.
+ *
+ *	- if, ifelse, etc. push arguments to be executed here.
+ * They may be any kind of object whatever.
+ *
+ *	- Control operators (filenameforall, for, repeat, loop, forall,
+ * pathforall, run, stopped, ...) mark the stack by pushing whatever state
+ * they need to save or keep track of and then an object with type = t_null,
+ * attrs = a_executable, size = es_xxx (see below), and value.opproc = a
+ * cleanup procedure that will get called whenever the execution stack is
+ * about to get cut back beyond this point because of an error, stop, exit,
+ * or quit.  (Executable null objects can't ever appear on the e-stack
+ * otherwise: if a control operator pushes one, it gets popped immediately.)
+ * The cleanup procedure is called with esp pointing just BELOW the mark,
+ * i.e., the mark has already been popped.
+ *
+ * The loop operators also push whatever state they need,
+ * followed by an operator object that handles continuing the loop.
+ *
+ * Note that there are many internal operators that need to be handled like
+ * looping operators -- for example, all the 'show' operators, since they
+ * may call out to BuildChar procedures.
+ */
+
+/* Macro for marking the execution stack */
+#define make_mark_estack(ep, es_idx, proc)\
+  make_tasv(ep, t_null, a_executable, es_idx, opproc, proc)
+#define push_mark_estack(es_idx, proc)\
+  (++esp, make_mark_estack(esp, es_idx, proc))
+#define r_is_estack_mark(ep)\
+  r_has_type_attrs(ep, t_null, a_executable)
+#define estack_mark_index(ep) r_size(ep)
+#define set_estack_mark_index(ep, es_idx) r_set_size(ep, es_idx)
+
+/* Macro for pushing an operator on the execution stack */
+/* to represent a continuation procedure */
+#define make_op_estack(ep, proc)\
+  make_oper(ep, 0, proc)
+#define push_op_estack(proc)\
+  (++esp, make_op_estack(esp, proc))
+
+/* Macro to ensure enough room on the execution stack */
+#define check_estack(n)\
+  if ( esp > estop - (n) )\
+    { int es_code_ = ref_stack_extend(&e_stack, n);\
+      if ( es_code_ < 0 ) return es_code_;\
+    }
+
+/* Macro to ensure enough entries on the execution stack */
+#define check_esp(n)\
+  if ( esp < esbot + ((n) - 1) )\
+    { e_stack.requested = (n); return_error(e_ExecStackUnderflow); }
+
+/* Define the various kinds of execution stack marks. */
+#define es_other 0			/* internal use */
+#define es_show 1			/* show operators */
+#define es_for 2			/* iteration operators */
+#define es_stopped 3			/* stopped operator */
+
+/*
+ * Pop a given number of elements off the execution stack,
+ * executing cleanup procedures as necessary.
+ */
+void pop_estack(P1(uint));
+
+/*
+ * The execution stack is implemented as a linked list of blocks;
+ * operators that can push or pop an unbounded number of values, or that
+ * access the entire o-stack, must take this into account.  These are:
+ *	exit  .stop  .instopped  countexecstack  execstack  currentfile
+ *	pop_estack(exit, stop, error recovery)
+ *	gs_show_find(all the show operators)
+ * In addition, for e-stack entries created by control operators, we must
+ * ensure that the mark and its data are never separated.  We do this
+ * by ensuring that when splitting the top block, at least N items
+ * are kept in the new top block above the bottommost retained mark,
+ * where N is the largest number of data items associated with a mark.
+ * Finally, in order to avoid specific checks for underflowing a block,
+ * we put a guard entry at the bottom of each block except the top one
+ * that contains a procedure that returns an internal "exec stack block
+ * underflow" error.
+ */