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 #if defined(LIBC_SCCS) && !defined(lint) 34 static char *sccsid2 = "@(#)pmap_prot2.c 1.3 87/08/11 Copyr 1984 Sun Micro"; 35 static char *sccsid = "@(#)pmap_prot2.c 2.1 88/07/29 4.0 RPCSRC"; 36 #endif 37 #include <sys/cdefs.h> 38 __FBSDID("$FreeBSD$"); 39 40 /* 41 * pmap_prot2.c 42 * Protocol for the local binder service, or pmap. 43 * 44 * Copyright (C) 1984, Sun Microsystems, Inc. 45 */ 46 47 #include "namespace.h" 48 #include <assert.h> 49 50 #include <rpc/types.h> 51 #include <rpc/xdr.h> 52 #include <rpc/pmap_prot.h> 53 #include "un-namespace.h" 54 55 56 /* 57 * What is going on with linked lists? (!) 58 * First recall the link list declaration from pmap_prot.h: 59 * 60 * struct pmaplist { 61 * struct pmap pml_map; 62 * struct pmaplist *pml_map; 63 * }; 64 * 65 * Compare that declaration with a corresponding xdr declaration that 66 * is (a) pointer-less, and (b) recursive: 67 * 68 * typedef union switch (bool_t) { 69 * 70 * case TRUE: struct { 71 * struct pmap; 72 * pmaplist_t foo; 73 * }; 74 * 75 * case FALSE: struct {}; 76 * } pmaplist_t; 77 * 78 * Notice that the xdr declaration has no nxt pointer while 79 * the C declaration has no bool_t variable. The bool_t can be 80 * interpreted as ``more data follows me''; if FALSE then nothing 81 * follows this bool_t; if TRUE then the bool_t is followed by 82 * an actual struct pmap, and then (recursively) by the 83 * xdr union, pamplist_t. 84 * 85 * This could be implemented via the xdr_union primitive, though this 86 * would cause a one recursive call per element in the list. Rather than do 87 * that we can ``unwind'' the recursion 88 * into a while loop and do the union arms in-place. 89 * 90 * The head of the list is what the C programmer wishes to past around 91 * the net, yet is the data that the pointer points to which is interesting; 92 * this sounds like a job for xdr_reference! 93 */ 94 bool_t 95 xdr_pmaplist(XDR *xdrs, struct pmaplist **rp) 96 { 97 /* 98 * more_elements is pre-computed in case the direction is 99 * XDR_ENCODE or XDR_FREE. more_elements is overwritten by 100 * xdr_bool when the direction is XDR_DECODE. 101 */ 102 bool_t more_elements; 103 int freeing; 104 struct pmaplist **next = NULL; /* pacify gcc */ 105 106 assert(xdrs != NULL); 107 assert(rp != NULL); 108 109 freeing = (xdrs->x_op == XDR_FREE); 110 111 for (;;) { 112 more_elements = (bool_t)(*rp != NULL); 113 if (! xdr_bool(xdrs, &more_elements)) 114 return (FALSE); 115 if (! more_elements) 116 return (TRUE); /* we are done */ 117 /* 118 * the unfortunate side effect of non-recursion is that in 119 * the case of freeing we must remember the next object 120 * before we free the current object ... 121 */ 122 if (freeing) 123 next = &((*rp)->pml_next); 124 if (! xdr_reference(xdrs, (caddr_t *)rp, 125 (u_int)sizeof(struct pmaplist), (xdrproc_t)xdr_pmap)) 126 return (FALSE); 127 rp = (freeing) ? next : &((*rp)->pml_next); 128 } 129 } 130 131 132 /* 133 * xdr_pmaplist_ptr() is specified to take a PMAPLIST *, but is identical in 134 * functionality to xdr_pmaplist(). 135 */ 136 bool_t 137 xdr_pmaplist_ptr(XDR *xdrs, struct pmaplist *rp) 138 { 139 return xdr_pmaplist(xdrs, (struct pmaplist **)(void *)rp); 140 } 141