1 /* @(#)pmap_prot2.c 2.1 88/07/29 4.0 RPCSRC */ 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 #if !defined(lint) && defined(SCCSIDS) 31 static char sccsid[] = "@(#)pmap_prot2.c 1.3 87/08/11 Copyr 1984 Sun Micro"; 32 #endif 33 34 /* 35 * pmap_prot2.c 36 * Protocol for the local binder service, or pmap. 37 * 38 * Copyright (C) 1984, Sun Microsystems, Inc. 39 */ 40 41 #include <rpc/types.h> 42 #include <rpc/xdr.h> 43 #include <rpc/pmap_prot.h> 44 45 46 /* 47 * What is going on with linked lists? (!) 48 * First recall the link list declaration from pmap_prot.h: 49 * 50 * struct pmaplist { 51 * struct pmap pml_map; 52 * struct pmaplist *pml_map; 53 * }; 54 * 55 * Compare that declaration with a corresponding xdr declaration that 56 * is (a) pointer-less, and (b) recursive: 57 * 58 * typedef union switch (bool_t) { 59 * 60 * case TRUE: struct { 61 * struct pmap; 62 * pmaplist_t foo; 63 * }; 64 * 65 * case FALSE: struct {}; 66 * } pmaplist_t; 67 * 68 * Notice that the xdr declaration has no nxt pointer while 69 * the C declaration has no bool_t variable. The bool_t can be 70 * interpreted as ``more data follows me''; if FALSE then nothing 71 * follows this bool_t; if TRUE then the bool_t is followed by 72 * an actual struct pmap, and then (recursively) by the 73 * xdr union, pamplist_t. 74 * 75 * This could be implemented via the xdr_union primitive, though this 76 * would cause a one recursive call per element in the list. Rather than do 77 * that we can ``unwind'' the recursion 78 * into a while loop and do the union arms in-place. 79 * 80 * The head of the list is what the C programmer wishes to past around 81 * the net, yet is the data that the pointer points to which is interesting; 82 * this sounds like a job for xdr_reference! 83 */ 84 bool_t 85 xdr_pmaplist(xdrs, rp) 86 register XDR *xdrs; 87 register struct pmaplist **rp; 88 { 89 /* 90 * more_elements is pre-computed in case the direction is 91 * XDR_ENCODE or XDR_FREE. more_elements is overwritten by 92 * xdr_bool when the direction is XDR_DECODE. 93 */ 94 bool_t more_elements; 95 register int freeing = (xdrs->x_op == XDR_FREE); 96 register struct pmaplist **next; 97 98 while (TRUE) { 99 more_elements = (bool_t)(*rp != NULL); 100 if (! xdr_bool(xdrs, &more_elements)) 101 return (FALSE); 102 if (! more_elements) 103 return (TRUE); /* we are done */ 104 /* 105 * the unfortunate side effect of non-recursion is that in 106 * the case of freeing we must remember the next object 107 * before we free the current object ... 108 */ 109 if (freeing) 110 next = &((*rp)->pml_next); 111 if (! xdr_reference(xdrs, (caddr_t *)rp, 112 (u_int)sizeof(struct pmaplist), xdr_pmap)) 113 return (FALSE); 114 rp = (freeing) ? next : &((*rp)->pml_next); 115 } 116 } 117