1 /* $NetBSD: pmap_prot2.c,v 1.2 1995/02/25 03:01:50 cgd 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) 33 /*static char *sccsid = "from: @(#)pmap_prot2.c 1.3 87/08/11 Copyr 1984 Sun Micro";*/ 34 /*static char *sccsid = "from: @(#)pmap_prot2.c 2.1 88/07/29 4.0 RPCSRC";*/ 35 static char *rcsid = "$NetBSD: pmap_prot2.c,v 1.2 1995/02/25 03:01:50 cgd Exp $"; 36 #endif 37 38 /* 39 * pmap_prot2.c 40 * Protocol for the local binder service, or pmap. 41 * 42 * Copyright (C) 1984, Sun Microsystems, Inc. 43 */ 44 45 #include <rpc/types.h> 46 #include <rpc/xdr.h> 47 #include <rpc/pmap_prot.h> 48 49 50 /* 51 * What is going on with linked lists? (!) 52 * First recall the link list declaration from pmap_prot.h: 53 * 54 * struct pmaplist { 55 * struct pmap pml_map; 56 * struct pmaplist *pml_map; 57 * }; 58 * 59 * Compare that declaration with a corresponding xdr declaration that 60 * is (a) pointer-less, and (b) recursive: 61 * 62 * typedef union switch (bool_t) { 63 * 64 * case TRUE: struct { 65 * struct pmap; 66 * pmaplist_t foo; 67 * }; 68 * 69 * case FALSE: struct {}; 70 * } pmaplist_t; 71 * 72 * Notice that the xdr declaration has no nxt pointer while 73 * the C declaration has no bool_t variable. The bool_t can be 74 * interpreted as ``more data follows me''; if FALSE then nothing 75 * follows this bool_t; if TRUE then the bool_t is followed by 76 * an actual struct pmap, and then (recursively) by the 77 * xdr union, pamplist_t. 78 * 79 * This could be implemented via the xdr_union primitive, though this 80 * would cause a one recursive call per element in the list. Rather than do 81 * that we can ``unwind'' the recursion 82 * into a while loop and do the union arms in-place. 83 * 84 * The head of the list is what the C programmer wishes to past around 85 * the net, yet is the data that the pointer points to which is interesting; 86 * this sounds like a job for xdr_reference! 87 */ 88 bool_t 89 xdr_pmaplist(xdrs, rp) 90 register XDR *xdrs; 91 register struct pmaplist **rp; 92 { 93 /* 94 * more_elements is pre-computed in case the direction is 95 * XDR_ENCODE or XDR_FREE. more_elements is overwritten by 96 * xdr_bool when the direction is XDR_DECODE. 97 */ 98 bool_t more_elements; 99 register int freeing = (xdrs->x_op == XDR_FREE); 100 register struct pmaplist **next; 101 102 while (TRUE) { 103 more_elements = (bool_t)(*rp != NULL); 104 if (! xdr_bool(xdrs, &more_elements)) 105 return (FALSE); 106 if (! more_elements) 107 return (TRUE); /* we are done */ 108 /* 109 * the unfortunate side effect of non-recursion is that in 110 * the case of freeing we must remember the next object 111 * before we free the current object ... 112 */ 113 if (freeing) 114 next = &((*rp)->pml_next); 115 if (! xdr_reference(xdrs, (caddr_t *)rp, 116 (u_int)sizeof(struct pmaplist), xdr_pmap)) 117 return (FALSE); 118 rp = (freeing) ? next : &((*rp)->pml_next); 119 } 120 } 121