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 30 #if defined(LIBC_SCCS) && !defined(lint) 31 /*static char *sccsid = "from: @(#)pmap_prot2.c 1.3 87/08/11 Copyr 1984 Sun Micro";*/ 32 /*static char *sccsid = "from: @(#)pmap_prot2.c 2.1 88/07/29 4.0 RPCSRC";*/ 33 static char *rcsid = "$Id: pmap_prot2.c,v 1.3 1996/06/10 20:13:05 jraynard Exp $"; 34 #endif 35 36 /* 37 * pmap_prot2.c 38 * Protocol for the local binder service, or pmap. 39 * 40 * Copyright (C) 1984, Sun Microsystems, Inc. 41 */ 42 43 #include <rpc/types.h> 44 #include <rpc/xdr.h> 45 #include <rpc/pmap_prot.h> 46 47 48 /* 49 * What is going on with linked lists? (!) 50 * First recall the link list declaration from pmap_prot.h: 51 * 52 * struct pmaplist { 53 * struct pmap pml_map; 54 * struct pmaplist *pml_map; 55 * }; 56 * 57 * Compare that declaration with a corresponding xdr declaration that 58 * is (a) pointer-less, and (b) recursive: 59 * 60 * typedef union switch (bool_t) { 61 * 62 * case TRUE: struct { 63 * struct pmap; 64 * pmaplist_t foo; 65 * }; 66 * 67 * case FALSE: struct {}; 68 * } pmaplist_t; 69 * 70 * Notice that the xdr declaration has no nxt pointer while 71 * the C declaration has no bool_t variable. The bool_t can be 72 * interpreted as ``more data follows me''; if FALSE then nothing 73 * follows this bool_t; if TRUE then the bool_t is followed by 74 * an actual struct pmap, and then (recursively) by the 75 * xdr union, pamplist_t. 76 * 77 * This could be implemented via the xdr_union primitive, though this 78 * would cause a one recursive call per element in the list. Rather than do 79 * that we can ``unwind'' the recursion 80 * into a while loop and do the union arms in-place. 81 * 82 * The head of the list is what the C programmer wishes to past around 83 * the net, yet is the data that the pointer points to which is interesting; 84 * this sounds like a job for xdr_reference! 85 */ 86 bool_t 87 xdr_pmaplist(xdrs, rp) 88 register XDR *xdrs; 89 register struct pmaplist **rp; 90 { 91 /* 92 * more_elements is pre-computed in case the direction is 93 * XDR_ENCODE or XDR_FREE. more_elements is overwritten by 94 * xdr_bool when the direction is XDR_DECODE. 95 */ 96 bool_t more_elements; 97 register int freeing = (xdrs->x_op == XDR_FREE); 98 register struct pmaplist **next = NULL; 99 100 while (TRUE) { 101 more_elements = (bool_t)(*rp != NULL); 102 if (! xdr_bool(xdrs, &more_elements)) 103 return (FALSE); 104 if (! more_elements) 105 return (TRUE); /* we are done */ 106 /* 107 * the unfortunate side effect of non-recursion is that in 108 * the case of freeing we must remember the next object 109 * before we free the current object ... 110 */ 111 if (freeing) 112 next = &((*rp)->pml_next); 113 if (! xdr_reference(xdrs, (caddr_t *)rp, 114 (u_int)sizeof(struct pmaplist), xdr_pmap)) 115 return (FALSE); 116 rp = (freeing) ? next : &((*rp)->pml_next); 117 } 118 } 119