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 */ 87 bool_t 88 xdr_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 */ 129 bool_t 130 xdr_pmaplist_ptr(XDR *xdrs, struct pmaplist *rp) 131 { 132 return xdr_pmaplist(xdrs, (struct pmaplist **)(void *)rp); 133 } 134