lib/libc/rpc/pmap_prot2.c

   1 /*
   2  * Sun RPC is a product of Sun Microsystems, Inc. and is provided for
   3  * unrestricted use provided that this legend is included on all tape
   4  * media and as a part of the software program in whole or part.  Users
   5  * may copy or modify Sun RPC without charge, but are not authorized
   6  * to license or distribute it to anyone else except as part of a product or
   7  * program developed by the user.
   8  *
   9  * SUN RPC IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING THE
  10  * WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
  11  * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
  12  *
  13  * Sun RPC is provided with no support and without any obligation on the
  14  * part of Sun Microsystems, Inc. to assist in its use, correction,
  15  * modification or enhancement.
  16  *
  17  * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
  18  * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY SUN RPC
  19  * OR ANY PART THEREOF.
  20  *
  21  * In no event will Sun Microsystems, Inc. be liable for any lost revenue
  22  * or profits or other special, indirect and consequential damages, even if
  23  * Sun has been advised of the possibility of such damages.
  24  *
  25  * Sun Microsystems, Inc.
  26  * 2550 Garcia Avenue
  27  * Mountain View, California  94043
  28  *
  29  * @(#)pmap_prot2.c 1.3 87/08/11 Copyr 1984 Sun Micro
  30  * @(#)pmap_prot2.c     2.1 88/07/29 4.0 RPCSRC
  31  * $NetBSD: pmap_prot2.c,v 1.14 2000/07/06 03:10:34 christos Exp $
  32  * $FreeBSD: src/lib/libc/rpc/pmap_prot2.c,v 1.10 2004/10/16 06:11:35 obrien Exp $
  33  * $DragonFly: src/lib/libc/rpc/pmap_prot2.c,v 1.4 2005/11/13 12:27:04 swildner Exp $
  34  */
  35
  36 /*
  37  * pmap_prot2.c
  38  * Protocol for the local binder service, or pmap.
  39  *
  40  * Copyright (C) 1984, Sun Microsystems, Inc.
  41  */
  42
  43 #include "namespace.h"
  44 #include <assert.h>
  45
  46 #include <rpc/types.h>
  47 #include <rpc/xdr.h>
  48 #include <rpc/pmap_prot.h>
  49 #include "un-namespace.h"
  50
  51
  52 /*
  53  * What is going on with linked lists? (!)
  54  * First recall the link list declaration from pmap_prot.h:
  55  *
  56  * struct pmaplist {
  57  *      struct pmap pml_map;
  58  *      struct pmaplist *pml_map;
  59  * };
  60  *
  61  * Compare that declaration with a corresponding xdr declaration that
  62  * is (a) pointer-less, and (b) recursive:
  63  *
  64  * typedef union switch (bool_t) {
  65  *
  66  *      case TRUE: struct {
  67  *              struct pmap;
  68  *              pmaplist_t foo;
  69  *      };
  70  *
  71  *      case FALSE: struct {};
  72  * } pmaplist_t;
  73  *
  74  * Notice that the xdr declaration has no nxt pointer while
  75  * the C declaration has no bool_t variable.  The bool_t can be
  76  * interpreted as ``more data follows me''; if FALSE then nothing
  77  * follows this bool_t; if TRUE then the bool_t is followed by
  78  * an actual struct pmap, and then (recursively) by the
  79  * xdr union, pamplist_t.
  80  *
  81  * This could be implemented via the xdr_union primitive, though this
  82  * would cause a one recursive call per element in the list.  Rather than do
  83  * that we can ``unwind'' the recursion
  84  * into a while loop and do the union arms in-place.
  85  *
  86  * The head of the list is what the C programmer wishes to past around
  87  * the net, yet is the data that the pointer points to which is interesting;
  88  * this sounds like a job for xdr_reference!
  89  */
  90 bool_t
  91 xdr_pmaplist(XDR *xdrs, struct pmaplist **rp)
  92 {
  93         /*
  94          * more_elements is pre-computed in case the direction is
  95          * XDR_ENCODE or XDR_FREE.  more_elements is overwritten by
  96          * xdr_bool when the direction is XDR_DECODE.
  97          */
  98         bool_t more_elements;
  99         int freeing;
 100         struct pmaplist **next  = NULL; /* pacify gcc */
 101
 102         assert(xdrs != NULL);
 103         assert(rp != NULL);
 104
 105         freeing = (xdrs->x_op == XDR_FREE);
 106
 107         for (;;) {
 108                 more_elements = (bool_t)(*rp != NULL);
 109                 if (! xdr_bool(xdrs, &more_elements))
 110                         return (FALSE);
 111                 if (! more_elements)
 112                         return (TRUE);  /* we are done */
 113                 /*
 114                  * the unfortunate side effect of non-recursion is that in
 115                  * the case of freeing we must remember the next object
 116                  * before we free the current object ...
 117                  */
 118                 if (freeing)
 119                         next = &((*rp)->pml_next);
 120                 if (! xdr_reference(xdrs, (caddr_t *)rp,
 121                     (u_int)sizeof(struct pmaplist), (xdrproc_t)xdr_pmap))
 122                         return (FALSE);
 123                 rp = (freeing) ? next : &((*rp)->pml_next);
 124         }
 125 }
 126
 127
 128 /*
 129  * xdr_pmaplist_ptr() is specified to take a PMAPLIST *, but is identical in
 130  * functionality to xdr_pmaplist().
 131  */
 132 bool_t
 133 xdr_pmaplist_ptr(XDR *xdrs, struct pmaplist *rp)
 134 {
 135         return xdr_pmaplist(xdrs, (struct pmaplist **)(void *)rp);
 136 }