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/* Copyright (C) 1991, 1994, 1996, 1998, 1999 Aladdin Enterprises. All rights reserved.
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This software is provided AS-IS with no warranty, either express or
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implied.
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This software is distributed under license and may not be copied,
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modified or distributed except as expressly authorized under the terms
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of the license contained in the file LICENSE in this distribution.
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For more information about licensing, please refer to
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http://www.ghostscript.com/licensing/. For information on
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commercial licensing, go to http://www.artifex.com/licensing/ or
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contact Artifex Software, Inc., 101 Lucas Valley Road #110,
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San Rafael, CA 94903, U.S.A., +1(415)492-9861.
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*/
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/* $Id: ostack.h,v 1.4 2002/02/21 22:24:53 giles Exp $ */
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/* Definitions for Ghostscript operand stack */
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#ifndef ostack_INCLUDED
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# define ostack_INCLUDED
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#include "iostack.h"
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#include "icstate.h" /* for access to op_stack */
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/* Define the operand stack pointers for operators. */
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#define iop_stack (i_ctx_p->op_stack)
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#define o_stack (iop_stack.stack)
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#define osbot (o_stack.bot)
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#define osp (o_stack.p)
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#define ostop (o_stack.top)
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/* Macro to ensure enough room on the operand stack */
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#define check_ostack(n)\
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if ( ostop - osp < (n) )\
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{ o_stack.requested = (n); return_error(e_stackoverflow); }
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/* Operand stack manipulation. */
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/* Note that push sets osp to (the new value of) op. */
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#define push(n)\
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BEGIN\
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if ( (op += (n)) > ostop )\
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{ o_stack.requested = (n); return_error(e_stackoverflow); }\
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else osp = op;\
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END
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/*
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* Note that the pop macro only decrements osp, not op. For this reason,
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*
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* >>> pop should only be used just before returning, <<<
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* >>> or else op must be decremented explicitly. <<<
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*/
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#define pop(n) (osp -= (n))
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/*
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* Note that the interpreter does not check for operand stack underflow
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* before calling the operator procedure. There are "guard" entries
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* with invalid types and attributes just below the bottom of the
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* operand stack: if the operator returns with a typecheck error,
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* the interpreter checks for underflow at that time.
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* Operators that don't typecheck their arguments must check for
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* operand stack underflow explicitly; operators that take a variable
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* number of arguments must also check for stack underflow in those cases
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* where they expect more than their minimum number of arguments.
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* (This is because the interpreter can only recognize that a typecheck
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* is really a stackunderflow when the stack has fewer than the
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* operator's declared minimum number of entries.)
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*/
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#define check_op(nargs)\
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if ( op < osbot + ((nargs) - 1) ) return_error(e_stackunderflow)
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/*
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* Similarly, in order to simplify some overflow checks, we allocate
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* a few guard entries just above the top of the o-stack.
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*/
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/*
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* The operand stack is implemented as a linked list of blocks:
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* operators that can push or pop an unbounded number of values, or that
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* access the entire o-stack, must take this into account. These are:
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* (int)copy index roll clear count cleartomark
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* counttomark aload astore packedarray
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* .get/.putdeviceparams .gethardwareparams
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*/
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#endif /* ostack_INCLUDED */
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