1 /* 2 * Sun RPC is a product of Sun Microsystems, Inc. and is provided for 3 * unrestricted use provided that this legend is included on all tape 4 * media and as a part of the software program in whole or part. Users 5 * may copy or modify Sun RPC without charge, but are not authorized 6 * to license or distribute it to anyone else except as part of a product or 7 * program developed by the user. 8 * 9 * SUN RPC IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING THE 10 * WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR 11 * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE. 12 * 13 * Sun RPC is provided with no support and without any obligation on the 14 * part of Sun Microsystems, Inc. to assist in its use, correction, 15 * modification or enhancement. 16 * 17 * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE 18 * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY SUN RPC 19 * OR ANY PART THEREOF. 20 * 21 * In no event will Sun Microsystems, Inc. be liable for any lost revenue 22 * or profits or other special, indirect and consequential damages, even if 23 * Sun has been advised of the possibility of such damages. 24 * 25 * Sun Microsystems, Inc. 26 * 2550 Garcia Avenue 27 * Mountain View, California 94043 28 * 29 * @(#)pmap_prot2.c 1.3 87/08/11 Copyr 1984 Sun Micro 30 * @(#)pmap_prot2.c 2.1 88/07/29 4.0 RPCSRC 31 * $FreeBSD: src/lib/libc/rpc/pmap_prot2.c,v 1.7 1999/08/28 00:00:42 peter Exp $ 32 * $DragonFly: src/lib/libc/rpc/pmap_prot2.c,v 1.3 2004/10/25 19:38:02 drhodus Exp $ 33 */ 34 35 /* 36 * pmap_prot2.c 37 * Protocol for the local binder service, or pmap. 38 * 39 * Copyright (C) 1984, Sun Microsystems, Inc. 40 */ 41 42 #include <rpc/types.h> 43 #include <rpc/xdr.h> 44 #include <rpc/pmap_prot.h> 45 46 47 /* 48 * What is going on with linked lists? (!) 49 * First recall the link list declaration from pmap_prot.h: 50 * 51 * struct pmaplist { 52 * struct pmap pml_map; 53 * struct pmaplist *pml_map; 54 * }; 55 * 56 * Compare that declaration with a corresponding xdr declaration that 57 * is (a) pointer-less, and (b) recursive: 58 * 59 * typedef union switch (bool_t) { 60 * 61 * case TRUE: struct { 62 * struct pmap; 63 * pmaplist_t foo; 64 * }; 65 * 66 * case FALSE: struct {}; 67 * } pmaplist_t; 68 * 69 * Notice that the xdr declaration has no nxt pointer while 70 * the C declaration has no bool_t variable. The bool_t can be 71 * interpreted as ``more data follows me''; if FALSE then nothing 72 * follows this bool_t; if TRUE then the bool_t is followed by 73 * an actual struct pmap, and then (recursively) by the 74 * xdr union, pamplist_t. 75 * 76 * This could be implemented via the xdr_union primitive, though this 77 * would cause a one recursive call per element in the list. Rather than do 78 * that we can ``unwind'' the recursion 79 * into a while loop and do the union arms in-place. 80 * 81 * The head of the list is what the C programmer wishes to past around 82 * the net, yet is the data that the pointer points to which is interesting; 83 * this sounds like a job for xdr_reference! 84 */ 85 bool_t 86 xdr_pmaplist(xdrs, rp) 87 XDR *xdrs; 88 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 = (xdrs->x_op == XDR_FREE); 97 struct pmaplist **next = NULL; 98 99 while (TRUE) { 100 more_elements = (bool_t)(*rp != NULL); 101 if (! xdr_bool(xdrs, &more_elements)) 102 return (FALSE); 103 if (! more_elements) 104 return (TRUE); /* we are done */ 105 /* 106 * the unfortunate side effect of non-recursion is that in 107 * the case of freeing we must remember the next object 108 * before we free the current object ... 109 */ 110 if (freeing) 111 next = &((*rp)->pml_next); 112 if (! xdr_reference(xdrs, (caddr_t *)rp, 113 (u_int)sizeof(struct pmaplist), xdr_pmap)) 114 return (FALSE); 115 rp = (freeing) ? next : &((*rp)->pml_next); 116 } 117 } 118