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/* $OpenBSD: pmap_prot2.c,v 1.7 2010/09/01 14:43:34 millert 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
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* 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);
}
}
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