/*

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Copyright 1992, 1993, 1994 Sun Microsystems, Inc.  Printed in the United
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This product is protected by copyright and distributed under the following
license restricting its use.

The Interface Definition Language Compiler Front End (CFE) is made
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this product is incorporated in whole or part. You may copy and extend
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and documentation for the Interface Definition Language CFE.

INTERFACE DEFINITION LANGUAGE CFE IS PROVIDED AS IS WITH NO WARRANTIES OF
ANY KIND INCLUDING THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS
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 */

/*
 * ast_recursive.cc - Check whether a type is used recursively in a situation
 *		      where this use would be illegal.
 *
 * EXPLANATION: The CORBAS says that the only legal use of recursive types is
 * in a manifest sequence declared inside a struct or union whose base type is
 * the struct or union
 *
 * ALGORITH FOR CHECK:
 * Sequences push a NULL on the scope stack to mark where in the scope nesting
 * they appear.
 *
 * - If the type is not a struct or union, return FALSE (legal use of type)
 * - Otherwise check up the scope stack, looking for this base type. If we
 *   find a NULL return FALSE (legal use of type, since it is inside some
 *   sequence). If we find the type on the stack, return TRUE (illegal use
 *   since it was not bracketed by a sequence). If we don't find the base
 *   type nor a sequence, return FALSE (legal use, since we're not nested).
 */

#include	<idl.hh>
#include	<idl_extern.hh>

/*
 * FE_illegal_recursive_type() - Implement the algorithm described above
 */
idl_bool
AST_illegal_recursive_type(AST_Decl *t)
{
  UTL_ScopeStackActiveIterator *i;
  UTL_Scope		       *s;
  AST_Structure		       *st1 = NULL, *st2;
  AST_Union		       *un1 = NULL, *un2;
  idl_bool		       check_for_struct = I_FALSE,
			       check_for_union = I_FALSE;

  if (t == NULL) return I_FALSE;
  
  /*
   * We only care about structs and unions
   */
  if (t->node_type() != AST_Decl::NT_struct &&
      t->node_type() != AST_Decl::NT_union)
    return I_FALSE;	// NOT ILLEGAL
  /*
   * Narrow the type appropriately so comparison will work
   */
  if (t->node_type() == AST_Decl::NT_struct) {
    check_for_struct = I_TRUE;
    st1 = AST_Structure::narrow_from_decl(t);
    if (st1 == NULL)
      return I_FALSE;	// NOT ILLEGAL
  } else if (t->node_type() == AST_Decl::NT_union) {
    check_for_union = I_TRUE;
    un1 = AST_Union::narrow_from_decl(t);
    if (un1 == NULL)
      return I_FALSE;	// NOT ILLEGAL
  }
  /*
   * OK, iterate up the stack
   */
  i = new UTL_ScopeStackActiveIterator(idl_global->scopes());
  while (!(i->is_done())) {
    s = i->item();
    /*
     * If we hit a NULL we're done since it means that we're nested inside
     * a sequence, where recursive types may be used
     */
    if (s == NULL) {
      delete i;
      return I_FALSE;	// NOT ILLEGAL
    }
    /*
     * OK, must check this scope
     */
    if (s->scope_node_type() == AST_Decl::NT_struct && check_for_struct) {
      st2 = AST_Structure::narrow_from_scope(s);
      if (st2 != NULL && st2 == st1) {
	delete i;
        return I_TRUE;	// ILLEGAL RECURSIVE TYPE USE
      }
    } else if (s->scope_node_type() == AST_Decl::NT_union &&
	       check_for_union) {
      un2 = AST_Union::narrow_from_scope(s);
      if (un2 != NULL && un2 == un1) {
        delete i;
	return I_TRUE;	// ILLEGAL RECURSIVE TYPE USE
      }
    }
    /*
     * This one is fine, get next item
     */
    i->next();
  }
  /*
   * No more scopes to check. This type was used legally
   */
  delete i;
  return I_FALSE;		// NOT ILLEGAL
}

