1/*	$NetBSD: pmap_prot2.c,v 1.14 2000/07/06 03:10:34 christos Exp $	*/
2
3/*-
4 * SPDX-License-Identifier: BSD-3-Clause
5 *
6 * Copyright (c) 2009, Sun Microsystems, Inc.
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions are met:
11 * - Redistributions of source code must retain the above copyright notice,
12 *   this list of conditions and the following disclaimer.
13 * - Redistributions in binary form must reproduce the above copyright notice,
14 *   this list of conditions and the following disclaimer in the documentation
15 *   and/or other materials provided with the distribution.
16 * - Neither the name of Sun Microsystems, 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 "AS IS"
21 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
24 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
25 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
26 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
27 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
28 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
29 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
30 * POSSIBILITY OF SUCH DAMAGE.
31 */
32
33/*
34 * pmap_prot2.c
35 * Protocol for the local binder service, or pmap.
36 *
37 * Copyright (C) 1984, Sun Microsystems, Inc.
38 */
39
40#include "namespace.h"
41#include <assert.h>
42
43#include <rpc/types.h>
44#include <rpc/xdr.h>
45#include <rpc/pmap_prot.h>
46#include "un-namespace.h"
47
48
49/*
50 * What is going on with linked lists? (!)
51 * First recall the link list declaration from pmap_prot.h:
52 *
53 * struct pmaplist {
54 *	struct pmap pml_map;
55 *	struct pmaplist *pml_map;
56 * };
57 *
58 * Compare that declaration with a corresponding xdr declaration that
59 * is (a) pointer-less, and (b) recursive:
60 *
61 * typedef union switch (bool_t) {
62 *
63 *	case TRUE: struct {
64 *		struct pmap;
65 * 		pmaplist_t foo;
66 *	};
67 *
68 *	case FALSE: struct {};
69 * } pmaplist_t;
70 *
71 * Notice that the xdr declaration has no nxt pointer while
72 * the C declaration has no bool_t variable.  The bool_t can be
73 * interpreted as ``more data follows me''; if FALSE then nothing
74 * follows this bool_t; if TRUE then the bool_t is followed by
75 * an actual struct pmap, and then (recursively) by the
76 * xdr union, pamplist_t.
77 *
78 * This could be implemented via the xdr_union primitive, though this
79 * would cause a one recursive call per element in the list.  Rather than do
80 * that we can ``unwind'' the recursion
81 * into a while loop and do the union arms in-place.
82 *
83 * The head of the list is what the C programmer wishes to past around
84 * the net, yet is the data that the pointer points to which is interesting;
85 * this sounds like a job for xdr_reference!
86 */
87bool_t
88xdr_pmaplist(XDR *xdrs, struct pmaplist **rp)
89{
90	/*
91	 * more_elements is pre-computed in case the direction is
92	 * XDR_ENCODE or XDR_FREE.  more_elements is overwritten by
93	 * xdr_bool when the direction is XDR_DECODE.
94	 */
95	bool_t more_elements;
96	int freeing;
97	struct pmaplist **next	= NULL; /* pacify gcc */
98
99	assert(xdrs != NULL);
100	assert(rp != NULL);
101
102	freeing = (xdrs->x_op == XDR_FREE);
103
104	for (;;) {
105		more_elements = (bool_t)(*rp != NULL);
106		if (! xdr_bool(xdrs, &more_elements))
107			return (FALSE);
108		if (! more_elements)
109			return (TRUE);  /* we are done */
110		/*
111		 * the unfortunate side effect of non-recursion is that in
112		 * the case of freeing we must remember the next object
113		 * before we free the current object ...
114		 */
115		if (freeing)
116			next = &((*rp)->pml_next);
117		if (! xdr_reference(xdrs, (caddr_t *)rp,
118		    (u_int)sizeof(struct pmaplist), (xdrproc_t)xdr_pmap))
119			return (FALSE);
120		rp = (freeing) ? next : &((*rp)->pml_next);
121	}
122}
123
124
125/*
126 * xdr_pmaplist_ptr() is specified to take a PMAPLIST *, but is identical in
127 * functionality to xdr_pmaplist().
128 */
129bool_t
130xdr_pmaplist_ptr(XDR *xdrs, struct pmaplist *rp)
131{
132	return xdr_pmaplist(xdrs, (struct pmaplist **)(void *)rp);
133}
134