pmap_prot2.c revision 92990 
1/*	$NetBSD: pmap_prot2.c,v 1.14 2000/07/06 03:10:34 christos Exp $	*/
2
3/*
4 * Sun RPC is a product of Sun Microsystems, Inc. and is provided for
5 * unrestricted use provided that this legend is included on all tape
6 * media and as a part of the software program in whole or part.  Users
7 * may copy or modify Sun RPC without charge, but are not authorized
8 * to license or distribute it to anyone else except as part of a product or
9 * program developed by the user.
10 *
11 * SUN RPC IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING THE
12 * WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
13 * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
14 *
15 * Sun RPC is provided with no support and without any obligation on the
16 * part of Sun Microsystems, Inc. to assist in its use, correction,
17 * modification or enhancement.
18 *
19 * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
20 * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY SUN RPC
21 * OR ANY PART THEREOF.
22 *
23 * In no event will Sun Microsystems, Inc. be liable for any lost revenue
24 * or profits or other special, indirect and consequential damages, even if
25 * Sun has been advised of the possibility of such damages.
26 *
27 * Sun Microsystems, Inc.
28 * 2550 Garcia Avenue
29 * Mountain View, California  94043
30 */
31
32#if defined(LIBC_SCCS) && !defined(lint)
33static char *sccsid = "@(#)pmap_prot2.c 1.3 87/08/11 Copyr 1984 Sun Micro";
34static char *sccsid = "@(#)pmap_prot2.c	2.1 88/07/29 4.0 RPCSRC";
35#endif
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD: head/lib/libc/rpc/pmap_prot2.c 92990 2002-03-22 23:18:37Z obrien $");
38
39/*
40 * pmap_prot2.c
41 * Protocol for the local binder service, or pmap.
42 *
43 * Copyright (C) 1984, Sun Microsystems, Inc.
44 */
45
46#include "namespace.h"
47#include <assert.h>
48
49#include <rpc/types.h>
50#include <rpc/xdr.h>
51#include <rpc/pmap_prot.h>
52#include "un-namespace.h"
53
54
55/*
56 * What is going on with linked lists? (!)
57 * First recall the link list declaration from pmap_prot.h:
58 *
59 * struct pmaplist {
60 *	struct pmap pml_map;
61 *	struct pmaplist *pml_map;
62 * };
63 *
64 * Compare that declaration with a corresponding xdr declaration that
65 * is (a) pointer-less, and (b) recursive:
66 *
67 * typedef union switch (bool_t) {
68 *
69 *	case TRUE: struct {
70 *		struct pmap;
71 * 		pmaplist_t foo;
72 *	};
73 *
74 *	case FALSE: struct {};
75 * } pmaplist_t;
76 *
77 * Notice that the xdr declaration has no nxt pointer while
78 * the C declaration has no bool_t variable.  The bool_t can be
79 * interpreted as ``more data follows me''; if FALSE then nothing
80 * follows this bool_t; if TRUE then the bool_t is followed by
81 * an actual struct pmap, and then (recursively) by the
82 * xdr union, pamplist_t.
83 *
84 * This could be implemented via the xdr_union primitive, though this
85 * would cause a one recursive call per element in the list.  Rather than do
86 * that we can ``unwind'' the recursion
87 * into a while loop and do the union arms in-place.
88 *
89 * The head of the list is what the C programmer wishes to past around
90 * the net, yet is the data that the pointer points to which is interesting;
91 * this sounds like a job for xdr_reference!
92 */
93bool_t
94xdr_pmaplist(xdrs, rp)
95	XDR *xdrs;
96	struct pmaplist **rp;
97{
98	/*
99	 * more_elements is pre-computed in case the direction is
100	 * XDR_ENCODE or XDR_FREE.  more_elements is overwritten by
101	 * xdr_bool when the direction is XDR_DECODE.
102	 */
103	bool_t more_elements;
104	int freeing;
105	struct pmaplist **next	= NULL; /* pacify gcc */
106
107	assert(xdrs != NULL);
108	assert(rp != NULL);
109
110	freeing = (xdrs->x_op == XDR_FREE);
111
112	for (;;) {
113		more_elements = (bool_t)(*rp != NULL);
114		if (! xdr_bool(xdrs, &more_elements))
115			return (FALSE);
116		if (! more_elements)
117			return (TRUE);  /* we are done */
118		/*
119		 * the unfortunate side effect of non-recursion is that in
120		 * the case of freeing we must remember the next object
121		 * before we free the current object ...
122		 */
123		if (freeing)
124			next = &((*rp)->pml_next);
125		if (! xdr_reference(xdrs, (caddr_t *)rp,
126		    (u_int)sizeof(struct pmaplist), (xdrproc_t)xdr_pmap))
127			return (FALSE);
128		rp = (freeing) ? next : &((*rp)->pml_next);
129	}
130}
131
132
133/*
134 * xdr_pmaplist_ptr() is specified to take a PMAPLIST *, but is identical in
135 * functionality to xdr_pmaplist().
136 */
137bool_t
138xdr_pmaplist_ptr(xdrs, rp)
139	XDR *xdrs;
140	struct pmaplist *rp;
141{
142	return xdr_pmaplist(xdrs, (struct pmaplist **)(void *)rp);
143}
144