/* Copyright (C) 2001-2006 Artifex Software, Inc.
All Rights Reserved.
This software is provided AS-IS with no warranty, either express or
This software is distributed under license and may not be copied, modified
or distributed except as expressly authorized under the terms of that
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/* $Id: oper.h 9043 2008-08-28 22:48:19Z giles $ */
/* Definitions for Ghostscript operators */
# define oper_INCLUDED
* Operator procedures take a single argument. This is currently a pointer
* to the current context state, but might conceivably change in the future.
* They return 0 for success, a negative code for an error, or a positive
* code for some uncommon situations (see below).
* In order to combine typecheck and stackunderflow error checking
* into a single test, we guard the bottom of the o-stack with
* additional entries of type t__invalid. However, if a type check fails,
* we must make an additional check to determine which error
* should be reported. In order not to have to make this check in-line
* in every type check in every operator, we define a procedure that takes
* an o-stack pointer and returns e_stackunderflow if it points to
* a guard entry, e_typecheck otherwise.
* Note that we only need to do this for typecheck, not for any other
* kind of error such as invalidaccess, since any operator that can
* generate the latter will do a check_type or a check_op first.
* (See ostack.h for more information.)
* We define the operand type of check_type_failed as const ref * rather than
* const_os_ptr simply because there are a number of routines that might
* be used either with a stack operand or with a general operand, and
* the check for t__invalid is harmless when applied to off-stack refs.
int check_type_failed(const ref *);
* Check the type of an object. Operators almost always use check_type,
* which includes the stack underflow check described just above;
* check_type_only is for checking subsidiary objects obtained from
* places other than the stack.
if ( !r_has_type(&orf,typ) ) return_op_typecheck(&orf)
if ( !r_has_stype(&orf,imemory,styp) ) return_op_typecheck(&orf)
if ( !r_has_type_attrs(&orf,typ,acc1) )\
return_error((!r_has_type(&orf,typ) ? check_type_failed(&orf) :\
/* Macro for as yet unimplemented operators. */
/* The if ( 1 ) is to prevent the compiler from complaining about */
/* unreachable code. */
#define NYI(msg) if ( 1 ) return_error(e_undefined)
* If an operator has popped or pushed something on the control stack,
* it must return o_pop_estack or o_push_estack respectively,
* rather than 0, to indicate success.
* It is OK to return o_pop_estack if nothing has been popped,
* but it is not OK to return o_push_estack if nothing has been pushed.
* If an operator has suspended the current context and wants the
* interpreter to call the scheduler, it must return o_reschedule.
* It may also have pushed or popped elements on the control stack.
* (This is only used when the Display PostScript option is included.)
* These values must be greater than 1, and far enough apart from zero and
* from each other not to tempt a compiler into implementing a 'switch'
* on them using indexing rather than testing.
#define o_push_estack 5
#define o_pop_estack 14
#define o_reschedule 22
#endif /* oper_INCLUDED */