1 /* $OpenBSD: pmap_prot2.c,v 1.6 2005/08/08 08:05:35 espie Exp $ */ 2 /* 3 * Sun RPC is a product of Sun Microsystems, Inc. and is provided for 4 * unrestricted use provided that this legend is included on all tape 5 * media and as a part of the software program in whole or part. Users 6 * may copy or modify Sun RPC without charge, but are not authorized 7 * to license or distribute it to anyone else except as part of a product or 8 * program developed by the user. 9 * 10 * SUN RPC IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING THE 11 * WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR 12 * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE. 13 * 14 * Sun RPC is provided with no support and without any obligation on the 15 * part of Sun Microsystems, Inc. to assist in its use, correction, 16 * modification or enhancement. 17 * 18 * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE 19 * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY SUN RPC 20 * OR ANY PART THEREOF. 21 * 22 * In no event will Sun Microsystems, Inc. be liable for any lost revenue 23 * or profits or other special, indirect and consequential damages, even if 24 * Sun has been advised of the possibility of such damages. 25 * 26 * Sun Microsystems, Inc. 27 * 2550 Garcia Avenue 28 * Mountain View, California 94043 29 */ 30 31 /* 32 * pmap_prot2.c 33 * Protocol for the local binder service, or pmap. 34 * 35 * Copyright (C) 1984, Sun Microsystems, Inc. 36 */ 37 38 #include <rpc/types.h> 39 #include <rpc/xdr.h> 40 #include <rpc/pmap_prot.h> 41 42 43 /* 44 * What is going on with linked lists? (!) 45 * First recall the link list declaration from pmap_prot.h: 46 * 47 * struct pmaplist { 48 * struct pmap pml_map; 49 * struct pmaplist *pml_map; 50 * }; 51 * 52 * Compare that declaration with a corresponding xdr declaration that 53 * is (a) pointer-less, and (b) recursive: 54 * 55 * typedef union switch (bool_t) { 56 * 57 * case TRUE: struct { 58 * struct pmap; 59 * pmaplist_t foo; 60 * }; 61 * 62 * case FALSE: struct {}; 63 * } pmaplist_t; 64 * 65 * Notice that the xdr declaration has no nxt pointer while 66 * the C declaration has no bool_t variable. The bool_t can be 67 * interpreted as ``more data follows me''; if FALSE then nothing 68 * follows this bool_t; if TRUE then the bool_t is followed by 69 * an actual struct pmap, and then (recursively) by the 70 * xdr union, pamplist_t. 71 * 72 * This could be implemented via the xdr_union primitive, though this 73 * would cause a one recursive call per element in the list. Rather than do 74 * that we can ``unwind'' the recursion 75 * into a while loop and do the union arms in-place. 76 * 77 * The head of the list is what the C programmer wishes to past around 78 * the net, yet is the data that the pointer points to which is interesting; 79 * this sounds like a job for xdr_reference! 80 */ 81 bool_t 82 xdr_pmaplist(XDR *xdrs, struct pmaplist **rp) 83 { 84 /* 85 * more_elements is pre-computed in case the direction is 86 * XDR_ENCODE or XDR_FREE. more_elements is overwritten by 87 * xdr_bool when the direction is XDR_DECODE. 88 */ 89 bool_t more_elements; 90 int freeing = (xdrs->x_op == XDR_FREE); 91 struct pmaplist **next; 92 93 while (TRUE) { 94 more_elements = (bool_t)(*rp != NULL); 95 if (! xdr_bool(xdrs, &more_elements)) 96 return (FALSE); 97 if (! more_elements) 98 return (TRUE); /* we are done */ 99 /* 100 * the unfortunate side effect of non-recursion is that in 101 * the case of freeing we must remember the next object 102 * before we free the current object ... 103 */ 104 if (freeing) 105 next = &((*rp)->pml_next); 106 if (! xdr_reference(xdrs, (caddr_t *)rp, 107 (u_int)sizeof(struct pmaplist), xdr_pmap)) 108 return (FALSE); 109 rp = (freeing) ? next : &((*rp)->pml_next); 110 } 111 } 112