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/* Copyright (C) 1989, 1995, 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: oper.h,v 1.6 2003/09/03 03:22:59 giles Exp $ */
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/* Definitions for Ghostscript operators */
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#ifndef oper_INCLUDED
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# define oper_INCLUDED
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#include "ierrors.h"
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#include "ostack.h"
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#include "opdef.h"
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#include "opextern.h"
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#include "opcheck.h"
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#include "iutil.h"
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/*
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* Operator procedures take a single argument. This is currently a pointer
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* to the current context state, but might conceivably change in the future.
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* They return 0 for success, a negative code for an error, or a positive
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* code for some uncommon situations (see below).
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*/
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/*
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* In order to combine typecheck and stackunderflow error checking
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* into a single test, we guard the bottom of the o-stack with
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* additional entries of type t__invalid. However, if a type check fails,
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* we must make an additional check to determine which error
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* should be reported. In order not to have to make this check in-line
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* in every type check in every operator, we define a procedure that takes
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* an o-stack pointer and returns e_stackunderflow if it points to
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* a guard entry, e_typecheck otherwise.
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*
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* Note that we only need to do this for typecheck, not for any other
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* kind of error such as invalidaccess, since any operator that can
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* generate the latter will do a check_type or a check_op first.
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* (See ostack.h for more information.)
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*
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* We define the operand type of check_type_failed as const ref * rather than
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* const_os_ptr simply because there are a number of routines that might
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* be used either with a stack operand or with a general operand, and
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* the check for t__invalid is harmless when applied to off-stack refs.
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*/
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int check_type_failed(const ref *);
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/*
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* Check the type of an object. Operators almost always use check_type,
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* which includes the stack underflow check described just above;
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* check_type_only is for checking subsidiary objects obtained from
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* places other than the stack.
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*/
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#define return_op_typecheck(op)\
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return_error(check_type_failed(op))
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#define check_type(orf,typ)\
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if ( !r_has_type(&orf,typ) ) return_op_typecheck(&orf)
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#define check_stype(orf,styp)\
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if ( !r_has_stype(&orf,imemory,styp) ) return_op_typecheck(&orf)
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#define check_array(orf)\
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check_array_else(orf, return_op_typecheck(&orf))
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#define check_type_access(orf,typ,acc1)\
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if ( !r_has_type_attrs(&orf,typ,acc1) )\
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return_error((!r_has_type(&orf,typ) ? check_type_failed(&orf) :\
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e_invalidaccess))
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#define check_read_type(orf,typ)\
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check_type_access(orf,typ,a_read)
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#define check_write_type(orf,typ)\
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check_type_access(orf,typ,a_write)
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/* Macro for as yet unimplemented operators. */
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/* The if ( 1 ) is to prevent the compiler from complaining about */
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/* unreachable code. */
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#define NYI(msg) if ( 1 ) return_error(e_undefined)
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/*
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* If an operator has popped or pushed something on the control stack,
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* it must return o_pop_estack or o_push_estack respectively,
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* rather than 0, to indicate success.
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* It is OK to return o_pop_estack if nothing has been popped,
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* but it is not OK to return o_push_estack if nothing has been pushed.
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*
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* If an operator has suspended the current context and wants the
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* interpreter to call the scheduler, it must return o_reschedule.
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* It may also have pushed or popped elements on the control stack.
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* (This is only used when the Display PostScript option is included.)
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*
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* These values must be greater than 1, and far enough apart from zero and
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* from each other not to tempt a compiler into implementing a 'switch'
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* on them using indexing rather than testing.
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*/
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#define o_push_estack 5
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#define o_pop_estack 14
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#define o_reschedule 22
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#endif /* oper_INCLUDED */
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