pmap_prot2.c revision 331722 
1/*	$NetBSD: pmap_prot2.c,v 1.14 2000/07/06 03:10:34 christos Exp $	*/
2
3/*-
4 * Copyright (c) 2009, Sun Microsystems, Inc.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions are met:
9 * - Redistributions of source code must retain the above copyright notice,
10 *   this list of conditions and the following disclaimer.
11 * - Redistributions in binary form must reproduce the above copyright notice,
12 *   this list of conditions and the following disclaimer in the documentation
13 *   and/or other materials provided with the distribution.
14 * - Neither the name of Sun Microsystems, Inc. nor the names of its
15 *   contributors may be used to endorse or promote products derived
16 *   from this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
19 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
22 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
23 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
24 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
25 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
26 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
27 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
28 * POSSIBILITY OF SUCH DAMAGE.
29 */
30
31#if defined(LIBC_SCCS) && !defined(lint)
32static char *sccsid2 = "@(#)pmap_prot2.c 1.3 87/08/11 Copyr 1984 Sun Micro";
33static char *sccsid = "@(#)pmap_prot2.c	2.1 88/07/29 4.0 RPCSRC";
34#endif
35#include <sys/cdefs.h>
36__FBSDID("$FreeBSD: stable/11/lib/libc/rpc/pmap_prot2.c 331722 2018-03-29 02:50:57Z eadler $");
37
38/*
39 * pmap_prot2.c
40 * Protocol for the local binder service, or pmap.
41 *
42 * Copyright (C) 1984, Sun Microsystems, Inc.
43 */
44
45#include "namespace.h"
46#include <assert.h>
47
48#include <rpc/types.h>
49#include <rpc/xdr.h>
50#include <rpc/pmap_prot.h>
51#include "un-namespace.h"
52
53
54/*
55 * What is going on with linked lists? (!)
56 * First recall the link list declaration from pmap_prot.h:
57 *
58 * struct pmaplist {
59 *	struct pmap pml_map;
60 *	struct pmaplist *pml_map;
61 * };
62 *
63 * Compare that declaration with a corresponding xdr declaration that
64 * is (a) pointer-less, and (b) recursive:
65 *
66 * typedef union switch (bool_t) {
67 *
68 *	case TRUE: struct {
69 *		struct pmap;
70 * 		pmaplist_t foo;
71 *	};
72 *
73 *	case FALSE: struct {};
74 * } pmaplist_t;
75 *
76 * Notice that the xdr declaration has no nxt pointer while
77 * the C declaration has no bool_t variable.  The bool_t can be
78 * interpreted as ``more data follows me''; if FALSE then nothing
79 * follows this bool_t; if TRUE then the bool_t is followed by
80 * an actual struct pmap, and then (recursively) by the
81 * xdr union, pamplist_t.
82 *
83 * This could be implemented via the xdr_union primitive, though this
84 * would cause a one recursive call per element in the list.  Rather than do
85 * that we can ``unwind'' the recursion
86 * into a while loop and do the union arms in-place.
87 *
88 * The head of the list is what the C programmer wishes to past around
89 * the net, yet is the data that the pointer points to which is interesting;
90 * this sounds like a job for xdr_reference!
91 */
92bool_t
93xdr_pmaplist(XDR *xdrs, struct pmaplist **rp)
94{
95	/*
96	 * more_elements is pre-computed in case the direction is
97	 * XDR_ENCODE or XDR_FREE.  more_elements is overwritten by
98	 * xdr_bool when the direction is XDR_DECODE.
99	 */
100	bool_t more_elements;
101	int freeing;
102	struct pmaplist **next	= NULL; /* pacify gcc */
103
104	assert(xdrs != NULL);
105	assert(rp != NULL);
106
107	freeing = (xdrs->x_op == XDR_FREE);
108
109	for (;;) {
110		more_elements = (bool_t)(*rp != NULL);
111		if (! xdr_bool(xdrs, &more_elements))
112			return (FALSE);
113		if (! more_elements)
114			return (TRUE);  /* we are done */
115		/*
116		 * the unfortunate side effect of non-recursion is that in
117		 * the case of freeing we must remember the next object
118		 * before we free the current object ...
119		 */
120		if (freeing)
121			next = &((*rp)->pml_next);
122		if (! xdr_reference(xdrs, (caddr_t *)rp,
123		    (u_int)sizeof(struct pmaplist), (xdrproc_t)xdr_pmap))
124			return (FALSE);
125		rp = (freeing) ? next : &((*rp)->pml_next);
126	}
127}
128
129
130/*
131 * xdr_pmaplist_ptr() is specified to take a PMAPLIST *, but is identical in
132 * functionality to xdr_pmaplist().
133 */
134bool_t
135xdr_pmaplist_ptr(XDR *xdrs, struct pmaplist *rp)
136{
137	return xdr_pmaplist(xdrs, (struct pmaplist **)(void *)rp);
138}
139