1 /* $OpenBSD: pmap_prot2.c,v 1.8 2015/09/13 15:36:56 guenther Exp $ */
2
3 /*
4 * Copyright (c) 2010, Oracle America, Inc.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions are
8 * met:
9 *
10 * * Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * * Redistributions in binary form must reproduce the above
13 * copyright notice, this list of conditions and the following
14 * disclaimer in the documentation and/or other materials
15 * provided with the distribution.
16 * * Neither the name of the "Oracle America, Inc." nor the names of its
17 * contributors may be used to endorse or promote products derived
18 * from this software without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
24 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
25 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
27 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
28 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
29 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
30 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
31 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32 */
33
34 /*
35 * pmap_prot2.c
36 * Protocol for the local binder service, or pmap.
37 */
38
39 #include <rpc/types.h>
40 #include <rpc/xdr.h>
41 #include <rpc/pmap_prot.h>
42
43
44 /*
45 * What is going on with linked lists? (!)
46 * First recall the link list declaration from pmap_prot.h:
47 *
48 * struct pmaplist {
49 * struct pmap pml_map;
50 * struct pmaplist *pml_map;
51 * };
52 *
53 * Compare that declaration with a corresponding xdr declaration that
54 * is (a) pointer-less, and (b) recursive:
55 *
56 * typedef union switch (bool_t) {
57 *
58 * case TRUE: struct {
59 * struct pmap;
60 * pmaplist_t foo;
61 * };
62 *
63 * case FALSE: struct {};
64 * } pmaplist_t;
65 *
66 * Notice that the xdr declaration has no nxt pointer while
67 * the C declaration has no bool_t variable. The bool_t can be
68 * interpreted as ``more data follows me''; if FALSE then nothing
69 * follows this bool_t; if TRUE then the bool_t is followed by
70 * an actual struct pmap, and then (recursively) by the
71 * xdr union, pamplist_t.
72 *
73 * This could be implemented via the xdr_union primitive, though this
74 * would cause a one recursive call per element in the list. Rather than do
75 * that we can ``unwind'' the recursion
76 * into a while loop and do the union arms in-place.
77 *
78 * The head of the list is what the C programmer wishes to past around
79 * the net, yet is the data that the pointer points to which is interesting;
80 * this sounds like a job for xdr_reference!
81 */
82 bool_t
xdr_pmaplist(XDR * xdrs,struct pmaplist ** rp)83 xdr_pmaplist(XDR *xdrs, struct pmaplist **rp)
84 {
85 /*
86 * more_elements is pre-computed in case the direction is
87 * XDR_ENCODE or XDR_FREE. more_elements is overwritten by
88 * xdr_bool when the direction is XDR_DECODE.
89 */
90 bool_t more_elements;
91 int freeing = (xdrs->x_op == XDR_FREE);
92 struct pmaplist **next;
93
94 while (TRUE) {
95 more_elements = (bool_t)(*rp != NULL);
96 if (! xdr_bool(xdrs, &more_elements))
97 return (FALSE);
98 if (! more_elements)
99 return (TRUE); /* we are done */
100 /*
101 * the unfortunate side effect of non-recursion is that in
102 * the case of freeing we must remember the next object
103 * before we free the current object ...
104 */
105 if (freeing)
106 next = &((*rp)->pml_next);
107 if (! xdr_reference(xdrs, (caddr_t *)rp,
108 (u_int)sizeof(struct pmaplist), xdr_pmap))
109 return (FALSE);
110 rp = (freeing) ? next : &((*rp)->pml_next);
111 }
112 }
113 DEF_WEAK(xdr_pmaplist);
114