rpc.subproj/pmap_prot2.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
   7  * Reserved.  This file contains Original Code and/or Modifications of
   8  * Original Code as defined in and that are subject to the Apple Public
   9  * Source License Version 1.1 (the "License").  You may not use this file
  10  * except in compliance with the License.  Please obtain a copy of the
  11  * License at http://www.apple.com/publicsource and read it before using
  12  * this file.
  13  *
  14  * The Original Code and all software distributed under the License are
  15  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  16  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  17  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT.  Please see the
  19  * License for the specific language governing rights and limitations
  20  * under the License.
  21  *
  22  * @APPLE_LICENSE_HEADER_END@
  23  */
  24 /*
  25  * Sun RPC is a product of Sun Microsystems, Inc. and is provided for
  26  * unrestricted use provided that this legend is included on all tape
  27  * media and as a part of the software program in whole or part.  Users
  28  * may copy or modify Sun RPC without charge, but are not authorized
  29  * to license or distribute it to anyone else except as part of a product or
  30  * program developed by the user.
  31  *
  32  * SUN RPC IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING THE
  33  * WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
  34  * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
  35  *
  36  * Sun RPC is provided with no support and without any obligation on the
  37  * part of Sun Microsystems, Inc. to assist in its use, correction,
  38  * modification or enhancement.
  39  *
  40  * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
  41  * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY SUN RPC
  42  * OR ANY PART THEREOF.
  43  *
  44  * In no event will Sun Microsystems, Inc. be liable for any lost revenue
  45  * or profits or other special, indirect and consequential damages, even if
  46  * Sun has been advised of the possibility of such damages.
  47  *
  48  * Sun Microsystems, Inc.
  49  * 2550 Garcia Avenue
  50  * Mountain View, California  94043
  51  */
  52
  53 #if defined(LIBC_SCCS) && !defined(lint)
  54 /*static char *sccsid = "from: @(#)pmap_prot2.c 1.3 87/08/11 Copyr 1984 Sun Micro";*/
  55 /*static char *sccsid = "from: @(#)pmap_prot2.c 2.1 88/07/29 4.0 RPCSRC";*/
  56 static char *rcsid = "$Id: pmap_prot2.c,v 1.2 1999/10/14 21:56:53 wsanchez Exp $";
  57 #endif
  58
  59 /*
  60  * pmap_prot2.c
  61  * Protocol for the local binder service, or pmap.
  62  *
  63  * Copyright (C) 1984, Sun Microsystems, Inc.
  64  */
  65
  66 #include <rpc/types.h>
  67 #include <rpc/xdr.h>
  68 #include <rpc/pmap_prot.h>
  69
  70
  71 /*
  72  * What is going on with linked lists? (!)
  73  * First recall the link list declaration from pmap_prot.h:
  74  *
  75  * struct pmaplist {
  76  *      struct pmap pml_map;
  77  *      struct pmaplist *pml_map;
  78  * };
  79  *
  80  * Compare that declaration with a corresponding xdr declaration that
  81  * is (a) pointer-less, and (b) recursive:
  82  *
  83  * typedef union switch (bool_t) {
  84  *
  85  *      case TRUE: struct {
  86  *              struct pmap;
  87  *              pmaplist_t foo;
  88  *      };
  89  *
  90  *      case FALSE: struct {};
  91  * } pmaplist_t;
  92  *
  93  * Notice that the xdr declaration has no nxt pointer while
  94  * the C declaration has no bool_t variable.  The bool_t can be
  95  * interpreted as ``more data follows me''; if FALSE then nothing
  96  * follows this bool_t; if TRUE then the bool_t is followed by
  97  * an actual struct pmap, and then (recursively) by the
  98  * xdr union, pamplist_t.
  99  *
 100  * This could be implemented via the xdr_union primitive, though this
 101  * would cause a one recursive call per element in the list.  Rather than do
 102  * that we can ``unwind'' the recursion
 103  * into a while loop and do the union arms in-place.
 104  *
 105  * The head of the list is what the C programmer wishes to past around
 106  * the net, yet is the data that the pointer points to which is interesting;
 107  * this sounds like a job for xdr_reference!
 108  */
 109 bool_t
 110 xdr_pmaplist(xdrs, rp)
 111         register XDR *xdrs;
 112         register struct pmaplist **rp;
 113 {
 114         /*
 115          * more_elements is pre-computed in case the direction is
 116          * XDR_ENCODE or XDR_FREE.  more_elements is overwritten by
 117          * xdr_bool when the direction is XDR_DECODE.
 118          */
 119         bool_t more_elements;
 120         register int freeing = (xdrs->x_op == XDR_FREE);
 121         register struct pmaplist **next;
 122
 123         while (TRUE) {
 124                 more_elements = (bool_t)(*rp != NULL);
 125                 if (! xdr_bool(xdrs, &more_elements))
 126                         return (FALSE);
 127                 if (! more_elements)
 128                         return (TRUE);  /* we are done */
 129                 /*
 130                  * the unfortunate side effect of non-recursion is that in
 131                  * the case of freeing we must remember the next object
 132                  * before we free the current object ...
 133                  */
 134                 if (freeing)
 135                         next = &((*rp)->pml_next);
 136                 if (! xdr_reference(xdrs, (caddr_t *)rp,
 137                     (u_int)sizeof(struct pmaplist), xdr_pmap))
 138                         return (FALSE);
 139                 rp = (freeing) ? next : &((*rp)->pml_next);
 140         }
 141 }