xref: /plan9/sys/src/cmd/gs/src/opdef.h (revision 593dc095aefb2a85c828727bbfa9da139a49bdf4)

/* Copyright (C) 1991, 1995, 1998, 1999 artofcode LLC.  All rights reserved.

  This software is provided AS-IS with no warranty, either express or
  implied.

  This software is distributed under license and may not be copied,
  modified or distributed except as expressly authorized under the terms
  of the license contained in the file LICENSE in this distribution.

  For more information about licensing, please refer to
  http://www.ghostscript.com/licensing/. For information on
  commercial licensing, go to http://www.artifex.com/licensing/ or
  contact Artifex Software, Inc., 101 Lucas Valley Road #110,
  San Rafael, CA  94903, U.S.A., +1(415)492-9861.
*/

/* $Id: opdef.h,v 1.6 2002/06/16 04:47:10 lpd Exp $ */
/* Operator definition interface for Ghostscript */

#ifndef opdef_INCLUDED
#  define opdef_INCLUDED

/*
 * Define the structure for initializing the operator table.  Each operator
 * file zxxx.c declares an array of these as follows:

   const op_def * const zxxx_op_defs[] = {
      {"1name", zname},
      ...
      op_def_end(iproc)
   };

 * where iproc is an initialization procedure for the file or 0, and, for
 * each operator defined, the initial digit of the name string indicates
 * the number of arguments and zname is the address of the associated C
 * function to invoke.
 *
 * The array definition always appears at the END of the file, to avoid
 * the need for forward declarations for all the operator procedures.
 *
 * Operators may be stored in dictionaries other than systemdict.
 * We support this with op_def entries of a special form:

   op_def_begin_dict("dictname"),

 */
typedef struct {
    const char *oname;
    op_proc_t proc;
} op_def;

#define op_def_begin_dict(dname) {dname, 0}
#define op_def_begin_filter() op_def_begin_dict("filterdict")
#define op_def_begin_level2() op_def_begin_dict("level2dict")
#define op_def_begin_ll3() op_def_begin_dict("ll3dict")
#define op_def_is_begin_dict(def) ((def)->proc == 0)
#define op_def_end(iproc) {0, iproc}

/*
 * NOTE: for implementation reasons, a single table of operator definitions
 * is limited to 16 entries, including op_def_begin_xxx entries.  If a file
 * defines more operators than this, it must split them into multiple
 * tables and have multiple -oper entries in the makefile.  Currently,
 * only 4 out of 85 operator files require this.
 */
#define OP_DEFS_LOG2_MAX_SIZE 4
#define OP_DEFS_MAX_SIZE (1 << OP_DEFS_LOG2_MAX_SIZE)

/*
 * Define the table of pointers to all operator definition tables.
 */
extern const op_def *const op_defs_all[];

/*
 * Internal operators whose names begin with %, such as continuation
 * operators, do not appear in systemdict.  Ghostscript assumes
 * that these operators cannot appear anywhere (in executable form)
 * except on the e-stack; to maintain this invariant, the execstack
 * operator converts them to literal form, and cvx refuses to convert
 * them back.  As a result of this invariant, they do not need to
 * push themselves back on the e-stack when executed, since the only
 * place they could have come from was the e-stack.
 */
#define op_def_is_internal(def) ((def)->oname[1] == '%')

/*
 * All operators are catalogued in a table; this is necessary because
 * they must have a short packed representation for the sake of 'bind'.
 * The `size' of an operator is normally its index in this table;
 * however, internal operators have a `size' of 0, and their true index
 * must be found by searching the table for their procedure address.
 */
ushort op_find_index(const ref *);

#define op_index(opref)\
  (r_size(opref) == 0 ? op_find_index(opref) : r_size(opref))

/*
 * There are actually two kinds of operators: the real ones (t_operator),
 * and ones defined by procedures (t_oparray).  The catalog for t_operators
 * is (indirectly) op_defs_all, and their index is in the range
 * [1..op_def_count-1].
 */
#define op_index_is_operator(index) ((index) < op_def_count)
extern const uint op_def_count;

#define op_index_def(index)\
  (&op_defs_all[(index) >> OP_DEFS_LOG2_MAX_SIZE]\
    [(index) & (OP_DEFS_MAX_SIZE - 1)])
#define op_num_args(opref) (op_index_def(op_index(opref))->oname[0] - '0')
#define op_index_proc(index) (op_index_def(index)->proc)

/*
 * There are two catalogs for t_oparrays, one global and one local.
 * Operator indices for the global table are in the range
 *      [op_def_count..op_def_count+op_array_global.count-1]
 * Operator indices for the local table are in the range
 *      [op_def_count+r_size(&op_array_global.table)..
 *        op_def_count+r_size(&op_array_global.table)+op_array_local.count-1]
 */
typedef struct op_array_table_s {
    ref table;			/* t_array */
    ushort *nx_table;		/* name indices */
    uint count;			/* # of occupied entries */
    uint base_index;		/* operator index of first entry */
    uint attrs;			/* ref attrs of ops in this table */
    ref *root_p;		/* self-pointer for GC root */
} op_array_table;
extern op_array_table
       op_array_table_global, op_array_table_local;

#define op_index_op_array_table(index)\
  ((index) < op_array_table_local.base_index ?\
   &op_array_table_global : &op_array_table_local)

/*
 * Convert an operator index to an operator or oparray ref.
 * This is only used for debugging and for 'get' from packed arrays,
 * so it doesn't have to be very fast.
 */
void op_index_ref(uint, ref *);

#endif /* opdef_INCLUDED */