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/* Copyright (C) 1992, 1993, 1994, 1996, 1997 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: ivmspace.h,v 1.4 2002/02/21 22:24:53 giles Exp $ */
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/* Local/global space management */
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/* Requires iref.h */
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#ifndef ivmspace_INCLUDED
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# define ivmspace_INCLUDED
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#include "gsgc.h"
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/*
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* r_space_bits and r_space_shift, which define the bits in a ref
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* that carry VM space information, are defined in iref.h.
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* r_space_bits must be at least 2.
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*/
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#define a_space (((1 << r_space_bits) - 1) << r_space_shift)
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/*
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* The i_vm_xxx values are defined in gsgc.h.
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*/
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typedef enum {
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avm_foreign = (i_vm_foreign << r_space_shift),
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avm_system = (i_vm_system << r_space_shift),
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avm_global = (i_vm_global << r_space_shift),
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avm_local = (i_vm_local << r_space_shift),
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avm_max = avm_local
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} avm_space;
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#define r_space(rp) (avm_space)(r_type_attrs(rp) & a_space)
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#define r_space_index(rp) ((int)r_space(rp) >> r_space_shift)
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#define r_set_space(rp,space) r_store_attrs(rp, a_space, (uint)space)
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/*
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* According to the PostScript language specification, attempting to store
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* a reference to a local object into a global object must produce an
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* invalidaccess error. However, systemdict must be able to refer to
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* a number of local dictionaries such as userdict and errordict.
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* Therefore, we implement a special hack in 'def' that allows such stores
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* if the dictionary being stored into is systemdict (which is normally
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* only writable during initialization) or a dictionary that appears
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* in systemdict (such as level2dict), and the current save level is zero
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* (to guarantee that we can't get dangling pointers).
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* We could allow this for any global dictionary, except that the garbage
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* collector must treat any such dictionaries as roots when collecting
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* local VM without collecting global VM.
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* We make a similar exception for .makeglobaloperator; this requires
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* treating the operator table as a GC root as well.
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*
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* We extend the local-into-global store check because we have four VM
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* spaces (local, global, system, and foreign), and we allow PostScript
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* programs to create objects in any of the first three. If we define
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* the "generation" of an object as foreign = 0, system = 1, global = 2,
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* and local = 3, then a store is legal iff the generation of the object
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* into which a pointer is being stored is greater than or equal to
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* the generation of the object into which the store is occurring.
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*
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* We must check for local-into-global stores in three categories of places:
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*
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* - The scanner, when it encounters a //name inside {}.
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*
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* - All operators that allocate ref-containing objects and also
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* store into them:
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* packedarray gstate makepattern?
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* makefont scalefont definefont filter
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*
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* - All operators that store refs into existing objects
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* ("operators" marked with * are actually PostScript procedures):
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* put(array) putinterval(array) astore copy(to array)
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* def store* put(dict) copy(dict)
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* dictstack execstack .make(global)operator
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* currentgstate defineusername
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*/
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/* Test whether an object is in local space, */
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/* which implies that we need not check when storing into it. */
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#define r_is_local(rp) (r_space(rp) == avm_local)
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/* Test whether an object is foreign, i.e., outside known space. */
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#define r_is_foreign(rp) (r_space(rp) == avm_foreign)
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/* Check whether a store is allowed. */
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#define store_check_space(destspace,rpnew)\
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if ( r_space(rpnew) > (destspace) )\
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return_error(e_invalidaccess)
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#define store_check_dest(rpdest,rpnew)\
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store_check_space(r_space(rpdest), rpnew)
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/* BACKWARD COMPATIBILITY (not used by any Ghostscript code per se) */
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#define check_store_space(rdest,rnewcont)\
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store_check_dest(&(rdest),&(rnewcont))
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#endif /* ivmspace_INCLUDED */
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