lib/libc/rpc/pmap_prot2.c

   1 /*      $NetBSD: pmap_prot2.c,v 1.16 2012/03/20 17:14:50 matt Exp $     */
   2
   3 /*
   4  * Sun RPC is a product of Sun Microsystems, Inc. and is provided for
   5  * unrestricted use provided that this legend is included on all tape
   6  * media and as a part of the software program in whole or part.  Users
   7  * may copy or modify Sun RPC without charge, but are not authorized
   8  * to license or distribute it to anyone else except as part of a product or
   9  * program developed by the user.
  10  *
  11  * SUN RPC IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING THE
  12  * WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
  13  * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
  14  *
  15  * Sun RPC is provided with no support and without any obligation on the
  16  * part of Sun Microsystems, Inc. to assist in its use, correction,
  17  * modification or enhancement.
  18  *
  19  * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
  20  * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY SUN RPC
  21  * OR ANY PART THEREOF.
  22  *
  23  * In no event will Sun Microsystems, Inc. be liable for any lost revenue
  24  * or profits or other special, indirect and consequential damages, even if
  25  * Sun has been advised of the possibility of such damages.
  26  *
  27  * Sun Microsystems, Inc.
  28  * 2550 Garcia Avenue
  29  * Mountain View, California  94043
  30  */
  31
  32 #include <sys/cdefs.h>
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 #if 0
  35 static char *sccsid = "@(#)pmap_prot2.c 1.3 87/08/11 Copyr 1984 Sun Micro";
  36 static char *sccsid = "@(#)pmap_prot2.c 2.1 88/07/29 4.0 RPCSRC";
  37 #else
  38 __RCSID("$NetBSD: pmap_prot2.c,v 1.16 2012/03/20 17:14:50 matt Exp $");
  39 #endif
  40 #endif
  41
  42 /*
  43  * pmap_prot2.c
  44  * Protocol for the local binder service, or pmap.
  45  *
  46  * Copyright (C) 1984, Sun Microsystems, Inc.
  47  */
  48
  49 #include "namespace.h"
  50
  51 #include <assert.h>
  52
  53 #include <rpc/types.h>
  54 #include <rpc/xdr.h>
  55 #include <rpc/pmap_prot.h>
  56
  57 #ifdef __weak_alias
  58 __weak_alias(xdr_pmaplist,_xdr_pmaplist)
  59 #endif
  60
  61 /*
  62  * What is going on with linked lists? (!)
  63  * First recall the link list declaration from pmap_prot.h:
  64  *
  65  * struct pmaplist {
  66  *      struct pmap pml_map;
  67  *      struct pmaplist *pml_map;
  68  * };
  69  *
  70  * Compare that declaration with a corresponding xdr declaration that
  71  * is (a) pointer-less, and (b) recursive:
  72  *
  73  * typedef union switch (bool_t) {
  74  *
  75  *      case TRUE: struct {
  76  *              struct pmap;
  77  *              pmaplist_t foo;
  78  *      };
  79  *
  80  *      case FALSE: struct {};
  81  * } pmaplist_t;
  82  *
  83  * Notice that the xdr declaration has no nxt pointer while
  84  * the C declaration has no bool_t variable.  The bool_t can be
  85  * interpreted as ``more data follows me''; if FALSE then nothing
  86  * follows this bool_t; if TRUE then the bool_t is followed by
  87  * an actual struct pmap, and then (recursively) by the
  88  * xdr union, pamplist_t.
  89  *
  90  * This could be implemented via the xdr_union primitive, though this
  91  * would cause a one recursive call per element in the list.  Rather than do
  92  * that we can ``unwind'' the recursion
  93  * into a while loop and do the union arms in-place.
  94  *
  95  * The head of the list is what the C programmer wishes to past around
  96  * the net, yet is the data that the pointer points to which is interesting;
  97  * this sounds like a job for xdr_reference!
  98  */
  99 bool_t
 100 xdr_pmaplist(XDR *xdrs, struct pmaplist **rp)
 101 {
 102         /*
 103          * more_elements is pre-computed in case the direction is
 104          * XDR_ENCODE or XDR_FREE.  more_elements is overwritten by
 105          * xdr_bool when the direction is XDR_DECODE.
 106          */
 107         bool_t more_elements;
 108         int freeing;
 109         struct pmaplist **next  = NULL; /* pacify gcc */
 110
 111         _DIAGASSERT(xdrs != NULL);
 112         _DIAGASSERT(rp != NULL);
 113
 114         freeing = (xdrs->x_op == XDR_FREE);
 115
 116         for (;;) {
 117                 more_elements = (bool_t)(*rp != NULL);
 118                 if (! xdr_bool(xdrs, &more_elements))
 119                         return (FALSE);
 120                 if (! more_elements)
 121                         return (TRUE);  /* we are done */
 122                 /*
 123                  * the unfortunate side effect of non-recursion is that in
 124                  * the case of freeing we must remember the next object
 125                  * before we free the current object ...
 126                  */
 127                 if (freeing)
 128                         next = &((*rp)->pml_next);
 129                 if (! xdr_reference(xdrs, (caddr_t *)rp,
 130                     (u_int)sizeof(struct pmaplist), (xdrproc_t)xdr_pmap))
 131                         return (FALSE);
 132                 rp = (freeing) ? next : &((*rp)->pml_next);
 133         }
 134 }
 135
 136
 137 /*
 138  * xdr_pmaplist_ptr() is specified to take a PMAPLIST *, but is identical in
 139  * functionality to xdr_pmaplist().
 140  */
 141 bool_t
 142 xdr_pmaplist_ptr(XDR *xdrs, struct pmaplist *rp)
 143 {
 144
 145         _DIAGASSERT(xdrs != NULL);
 146         _DIAGASSERT(rp != NULL);
 147
 148         return xdr_pmaplist(xdrs, (struct pmaplist **)(void *)rp);
 149 }