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pmap_prot2.c revision 1.15.60.1 
      1 /*	$NetBSD: pmap_prot2.c,v 1.15.60.1 2012/04/17 00:05:23 yamt 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 #include <sys/cdefs.h>
     33 #if defined(LIBC_SCCS) && !defined(lint)
     34 #if 0
     35 static char *sccsid = "@(#)pmap_prot2.c 1.3 87/08/11 Copyr 1984 Sun Micro";
     36 static char *sccsid = "@(#)pmap_prot2.c	2.1 88/07/29 4.0 RPCSRC";
     37 #else
     38 __RCSID("$NetBSD: pmap_prot2.c,v 1.15.60.1 2012/04/17 00:05:23 yamt Exp $");
     39 #endif
     40 #endif
     41 
     42 /*
     43  * pmap_prot2.c
     44  * Protocol for the local binder service, or pmap.
     45  *
     46  * Copyright (C) 1984, Sun Microsystems, Inc.
     47  */
     48 
     49 #include "namespace.h"
     50 
     51 #include <assert.h>
     52 
     53 #include <rpc/types.h>
     54 #include <rpc/xdr.h>
     55 #include <rpc/pmap_prot.h>
     56 
     57 #ifdef __weak_alias
     58 __weak_alias(xdr_pmaplist,_xdr_pmaplist)
     59 #endif
     60 
     61 /*
     62  * What is going on with linked lists? (!)
     63  * First recall the link list declaration from pmap_prot.h:
     64  *
     65  * struct pmaplist {
     66  *	struct pmap pml_map;
     67  *	struct pmaplist *pml_map;
     68  * };
     69  *
     70  * Compare that declaration with a corresponding xdr declaration that
     71  * is (a) pointer-less, and (b) recursive:
     72  *
     73  * typedef union switch (bool_t) {
     74  *
     75  *	case TRUE: struct {
     76  *		struct pmap;
     77  * 		pmaplist_t foo;
     78  *	};
     79  *
     80  *	case FALSE: struct {};
     81  * } pmaplist_t;
     82  *
     83  * Notice that the xdr declaration has no nxt pointer while
     84  * the C declaration has no bool_t variable.  The bool_t can be
     85  * interpreted as ``more data follows me''; if FALSE then nothing
     86  * follows this bool_t; if TRUE then the bool_t is followed by
     87  * an actual struct pmap, and then (recursively) by the
     88  * xdr union, pamplist_t.
     89  *
     90  * This could be implemented via the xdr_union primitive, though this
     91  * would cause a one recursive call per element in the list.  Rather than do
     92  * that we can ``unwind'' the recursion
     93  * into a while loop and do the union arms in-place.
     94  *
     95  * The head of the list is what the C programmer wishes to past around
     96  * the net, yet is the data that the pointer points to which is interesting;
     97  * this sounds like a job for xdr_reference!
     98  */
     99 bool_t
    100 xdr_pmaplist(XDR *xdrs, struct pmaplist **rp)
    101 {
    102 	/*
    103 	 * more_elements is pre-computed in case the direction is
    104 	 * XDR_ENCODE or XDR_FREE.  more_elements is overwritten by
    105 	 * xdr_bool when the direction is XDR_DECODE.
    106 	 */
    107 	bool_t more_elements;
    108 	int freeing;
    109 	struct pmaplist **next	= NULL; /* pacify gcc */
    110 
    111 	_DIAGASSERT(xdrs != NULL);
    112 	_DIAGASSERT(rp != NULL);
    113 
    114 	freeing = (xdrs->x_op == XDR_FREE);
    115 
    116 	for (;;) {
    117 		more_elements = (bool_t)(*rp != NULL);
    118 		if (! xdr_bool(xdrs, &more_elements))
    119 			return (FALSE);
    120 		if (! more_elements)
    121 			return (TRUE);  /* we are done */
    122 		/*
    123 		 * the unfortunate side effect of non-recursion is that in
    124 		 * the case of freeing we must remember the next object
    125 		 * before we free the current object ...
    126 		 */
    127 		if (freeing)
    128 			next = &((*rp)->pml_next);
    129 		if (! xdr_reference(xdrs, (caddr_t *)rp,
    130 		    (u_int)sizeof(struct pmaplist), (xdrproc_t)xdr_pmap))
    131 			return (FALSE);
    132 		rp = (freeing) ? next : &((*rp)->pml_next);
    133 	}
    134 }
    135 
    136 
    137 /*
    138  * xdr_pmaplist_ptr() is specified to take a PMAPLIST *, but is identical in
    139  * functionality to xdr_pmaplist().
    140  */
    141 bool_t
    142 xdr_pmaplist_ptr(XDR *xdrs, struct pmaplist *rp)
    143 {
    144 
    145 	_DIAGASSERT(xdrs != NULL);
    146 	_DIAGASSERT(rp != NULL);
    147 
    148 	return xdr_pmaplist(xdrs, (struct pmaplist **)(void *)rp);
    149 }
    150