/*      $OpenBSD: pmap_prot2.c,v 1.8 2015/09/13 15:36:56 guenther Exp $ */

/*
 * Copyright (c) 2010, Oracle America, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 *       copyright notice, this list of conditions and the following
 *       disclaimer in the documentation and/or other materials
 *       provided with the distribution.
 *     * Neither the name of the "Oracle America, Inc." nor the names of its
 *       contributors may be used to endorse or promote products derived
 *       from this software without specific prior written permission.
 *
 *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 *   FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 *   COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 *   INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 *   DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 *   GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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 *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * pmap_prot2.c
 * Protocol for the local binder service, or pmap.
 */

#include <rpc/types.h>
#include <rpc/xdr.h>
#include <rpc/pmap_prot.h>


/* 
 * What is going on with linked lists? (!)
 * First recall the link list declaration from pmap_prot.h:
 *
 * struct pmaplist {
 *      struct pmap pml_map;
 *      struct pmaplist *pml_map;
 * };
 *
 * Compare that declaration with a corresponding xdr declaration that 
 * is (a) pointer-less, and (b) recursive:
 *
 * typedef union switch (bool_t) {
 * 
 *      case TRUE: struct {
 *              struct pmap;
 *              pmaplist_t foo;
 *      };
 *
 *      case FALSE: struct {};
 * } pmaplist_t;
 *
 * Notice that the xdr declaration has no nxt pointer while
 * the C declaration has no bool_t variable.  The bool_t can be
 * interpreted as ``more data follows me''; if FALSE then nothing
 * follows this bool_t; if TRUE then the bool_t is followed by
 * an actual struct pmap, and then (recursively) by the 
 * xdr union, pamplist_t.  
 *
 * This could be implemented via the xdr_union primitive, though this
 * would cause a one recursive call per element in the list.  Rather than do
 * that we can ``unwind'' the recursion
 * into a while loop and do the union arms in-place.
 *
 * The head of the list is what the C programmer wishes to past around
 * the net, yet is the data that the pointer points to which is interesting;
 * this sounds like a job for xdr_reference!
 */
bool_t
xdr_pmaplist(XDR *xdrs, struct pmaplist **rp)
{
        /*
         * more_elements is pre-computed in case the direction is
         * XDR_ENCODE or XDR_FREE.  more_elements is overwritten by
         * xdr_bool when the direction is XDR_DECODE.
         */
        bool_t more_elements;
        int freeing = (xdrs->x_op == XDR_FREE);
        struct pmaplist **next;

        while (TRUE) {
                more_elements = (bool_t)(*rp != NULL);
                if (! xdr_bool(xdrs, &more_elements))
                        return (FALSE);
                if (! more_elements)
                        return (TRUE);  /* we are done */
                /*
                 * the unfortunate side effect of non-recursion is that in
                 * the case of freeing we must remember the next object
                 * before we free the current object ...
                 */
                if (freeing)
                        next = &((*rp)->pml_next); 
                if (! xdr_reference(xdrs, (caddr_t *)rp,
                    (u_int)sizeof(struct pmaplist), xdr_pmap))
                        return (FALSE);
                rp = (freeing) ? next : &((*rp)->pml_next);
        }
}
DEF_WEAK(xdr_pmaplist);