1 /* $NetBSD: pmap_prot2.c,v 1.4 1997/07/21 14:08:33 jtc 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 1.4 1997/07/21 14:08:33 jtc 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 #include <rpc/types.h> 51 #include <rpc/xdr.h> 52 #include <rpc/pmap_prot.h> 53 54 #ifdef __weak_alias 55 __weak_alias(xdr_pmaplist,_xdr_pmaplist); 56 #endif 57 58 /* 59 * What is going on with linked lists? (!) 60 * First recall the link list declaration from pmap_prot.h: 61 * 62 * struct pmaplist { 63 * struct pmap pml_map; 64 * struct pmaplist *pml_map; 65 * }; 66 * 67 * Compare that declaration with a corresponding xdr declaration that 68 * is (a) pointer-less, and (b) recursive: 69 * 70 * typedef union switch (bool_t) { 71 * 72 * case TRUE: struct { 73 * struct pmap; 74 * pmaplist_t foo; 75 * }; 76 * 77 * case FALSE: struct {}; 78 * } pmaplist_t; 79 * 80 * Notice that the xdr declaration has no nxt pointer while 81 * the C declaration has no bool_t variable. The bool_t can be 82 * interpreted as ``more data follows me''; if FALSE then nothing 83 * follows this bool_t; if TRUE then the bool_t is followed by 84 * an actual struct pmap, and then (recursively) by the 85 * xdr union, pamplist_t. 86 * 87 * This could be implemented via the xdr_union primitive, though this 88 * would cause a one recursive call per element in the list. Rather than do 89 * that we can ``unwind'' the recursion 90 * into a while loop and do the union arms in-place. 91 * 92 * The head of the list is what the C programmer wishes to past around 93 * the net, yet is the data that the pointer points to which is interesting; 94 * this sounds like a job for xdr_reference! 95 */ 96 bool_t 97 xdr_pmaplist(xdrs, rp) 98 register XDR *xdrs; 99 register struct pmaplist **rp; 100 { 101 /* 102 * more_elements is pre-computed in case the direction is 103 * XDR_ENCODE or XDR_FREE. more_elements is overwritten by 104 * xdr_bool when the direction is XDR_DECODE. 105 */ 106 bool_t more_elements; 107 register int freeing = (xdrs->x_op == XDR_FREE); 108 register struct pmaplist **next = NULL; /* pacify gcc */ 109 110 while (TRUE) { 111 more_elements = (bool_t)(*rp != NULL); 112 if (! xdr_bool(xdrs, &more_elements)) 113 return (FALSE); 114 if (! more_elements) 115 return (TRUE); /* we are done */ 116 /* 117 * the unfortunate side effect of non-recursion is that in 118 * the case of freeing we must remember the next object 119 * before we free the current object ... 120 */ 121 if (freeing) 122 next = &((*rp)->pml_next); 123 if (! xdr_reference(xdrs, (caddr_t *)rp, 124 (u_int)sizeof(struct pmaplist), xdr_pmap)) 125 return (FALSE); 126 rp = (freeing) ? next : &((*rp)->pml_next); 127 } 128 } 129