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