rpc.subproj/pmap_prot2.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*
  26  * Sun RPC is a product of Sun Microsystems, Inc. and is provided for
  27  * unrestricted use provided that this legend is included on all tape
  28  * media and as a part of the software program in whole or part.  Users
  29  * may copy or modify Sun RPC without charge, but are not authorized
  30  * to license or distribute it to anyone else except as part of a product or
  31  * program developed by the user.
  32  *
  33  * SUN RPC IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING THE
  34  * WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
  35  * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
  36  *
  37  * Sun RPC is provided with no support and without any obligation on the
  38  * part of Sun Microsystems, Inc. to assist in its use, correction,
  39  * modification or enhancement.
  40  *
  41  * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
  42  * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY SUN RPC
  43  * OR ANY PART THEREOF.
  44  *
  45  * In no event will Sun Microsystems, Inc. be liable for any lost revenue
  46  * or profits or other special, indirect and consequential damages, even if
  47  * Sun has been advised of the possibility of such damages.
  48  *
  49  * Sun Microsystems, Inc.
  50  * 2550 Garcia Avenue
  51  * Mountain View, California  94043
  52  */
  53
  54 #if defined(LIBC_SCCS) && !defined(lint)
  55 /*static char *sccsid = "from: @(#)pmap_prot2.c 1.3 87/08/11 Copyr 1984 Sun Micro";*/
  56 /*static char *sccsid = "from: @(#)pmap_prot2.c 2.1 88/07/29 4.0 RPCSRC";*/
  57 static char *rcsid = "$Id: pmap_prot2.c,v 1.3 2002/02/19 20:36:24 epeyton Exp $";
  58 #endif
  59
  60 /*
  61  * pmap_prot2.c
  62  * Protocol for the local binder service, or pmap.
  63  *
  64  * Copyright (C) 1984, Sun Microsystems, Inc.
  65  */
  66
  67 #include <rpc/types.h>
  68 #include <rpc/xdr.h>
  69 #include <rpc/pmap_prot.h>
  70
  71
  72 /*
  73  * What is going on with linked lists? (!)
  74  * First recall the link list declaration from pmap_prot.h:
  75  *
  76  * struct pmaplist {
  77  *      struct pmap pml_map;
  78  *      struct pmaplist *pml_map;
  79  * };
  80  *
  81  * Compare that declaration with a corresponding xdr declaration that
  82  * is (a) pointer-less, and (b) recursive:
  83  *
  84  * typedef union switch (bool_t) {
  85  *
  86  *      case TRUE: struct {
  87  *              struct pmap;
  88  *              pmaplist_t foo;
  89  *      };
  90  *
  91  *      case FALSE: struct {};
  92  * } pmaplist_t;
  93  *
  94  * Notice that the xdr declaration has no nxt pointer while
  95  * the C declaration has no bool_t variable.  The bool_t can be
  96  * interpreted as ``more data follows me''; if FALSE then nothing
  97  * follows this bool_t; if TRUE then the bool_t is followed by
  98  * an actual struct pmap, and then (recursively) by the
  99  * xdr union, pamplist_t.
 100  *
 101  * This could be implemented via the xdr_union primitive, though this
 102  * would cause a one recursive call per element in the list.  Rather than do
 103  * that we can ``unwind'' the recursion
 104  * into a while loop and do the union arms in-place.
 105  *
 106  * The head of the list is what the C programmer wishes to past around
 107  * the net, yet is the data that the pointer points to which is interesting;
 108  * this sounds like a job for xdr_reference!
 109  */
 110 bool_t
 111 xdr_pmaplist(xdrs, rp)
 112         register XDR *xdrs;
 113         register struct pmaplist **rp;
 114 {
 115         /*
 116          * more_elements is pre-computed in case the direction is
 117          * XDR_ENCODE or XDR_FREE.  more_elements is overwritten by
 118          * xdr_bool when the direction is XDR_DECODE.
 119          */
 120         bool_t more_elements;
 121         register int freeing = (xdrs->x_op == XDR_FREE);
 122         register struct pmaplist **next = NULL;
 123
 124         while (TRUE) {
 125                 more_elements = (bool_t)(*rp != NULL);
 126                 if (! xdr_bool(xdrs, &more_elements))
 127                         return (FALSE);
 128                 if (! more_elements)
 129                         return (TRUE);  /* we are done */
 130                 /*
 131                  * the unfortunate side effect of non-recursion is that in
 132                  * the case of freeing we must remember the next object
 133                  * before we free the current object ...
 134                  */
 135                 if (freeing)
 136                         next = &((*rp)->pml_next);
 137                 if (! xdr_reference(xdrs, (caddr_t *)rp,
 138                     (u_int)sizeof(struct pmaplist), xdr_pmap))
 139                         return (FALSE);
 140                 rp = (freeing) ? next : &((*rp)->pml_next);
 141         }
 142 }