1 /* $NetBSD: pmap_prot2.c,v 1.8 1998/11/15 17:32:43 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 #include <sys/cdefs.h> 33 #if defined(LIBC_SCCS) && !defined(lint) 34 #if 0 35 static char *sccsid = "@(#)pmap_prot2.c 1.3 87/08/11 Copyr 1984 Sun Micro"; 36 static char *sccsid = "@(#)pmap_prot2.c 2.1 88/07/29 4.0 RPCSRC"; 37 #else 38 __RCSID("$NetBSD: pmap_prot2.c,v 1.8 1998/11/15 17:32:43 christos Exp $"); 39 #endif 40 #endif 41 42 /* 43 * pmap_prot2.c 44 * Protocol for the local binder service, or pmap. 45 * 46 * Copyright (C) 1984, Sun Microsystems, Inc. 47 */ 48 49 #include "namespace.h" 50 51 #include <rpc/types.h> 52 #include <rpc/xdr.h> 53 #include <rpc/pmap_prot.h> 54 55 #ifdef __weak_alias 56 __weak_alias(xdr_pmaplist,_xdr_pmaplist); 57 #endif 58 59 /* 60 * What is going on with linked lists? (!) 61 * First recall the link list declaration from pmap_prot.h: 62 * 63 * struct pmaplist { 64 * struct pmap pml_map; 65 * struct pmaplist *pml_map; 66 * }; 67 * 68 * Compare that declaration with a corresponding xdr declaration that 69 * is (a) pointer-less, and (b) recursive: 70 * 71 * typedef union switch (bool_t) { 72 * 73 * case TRUE: struct { 74 * struct pmap; 75 * pmaplist_t foo; 76 * }; 77 * 78 * case FALSE: struct {}; 79 * } pmaplist_t; 80 * 81 * Notice that the xdr declaration has no nxt pointer while 82 * the C declaration has no bool_t variable. The bool_t can be 83 * interpreted as ``more data follows me''; if FALSE then nothing 84 * follows this bool_t; if TRUE then the bool_t is followed by 85 * an actual struct pmap, and then (recursively) by the 86 * xdr union, pamplist_t. 87 * 88 * This could be implemented via the xdr_union primitive, though this 89 * would cause a one recursive call per element in the list. Rather than do 90 * that we can ``unwind'' the recursion 91 * into a while loop and do the union arms in-place. 92 * 93 * The head of the list is what the C programmer wishes to past around 94 * the net, yet is the data that the pointer points to which is interesting; 95 * this sounds like a job for xdr_reference! 96 */ 97 bool_t 98 xdr_pmaplist(xdrs, rp) 99 XDR *xdrs; 100 struct pmaplist **rp; 101 { 102 /* 103 * more_elements is pre-computed in case the direction is 104 * XDR_ENCODE or XDR_FREE. more_elements is overwritten by 105 * xdr_bool when the direction is XDR_DECODE. 106 */ 107 bool_t more_elements; 108 int freeing = (xdrs->x_op == XDR_FREE); 109 struct pmaplist **next = NULL; /* pacify gcc */ 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), xdr_pmap)) 126 return (FALSE); 127 rp = (freeing) ? next : &((*rp)->pml_next); 128 } 129 } 130