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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 = "$FreeBSD: src/lib/libc/rpc/pmap_prot2.c,v 1.7 1999/08/28 00:00:42 peter Exp $";
38 * Protocol for the local binder service, or pmap.
40 * Copyright (C) 1984, Sun Microsystems, Inc.
43 #include <rpc/types.h>
45 #include <rpc/pmap_prot.h>
49 * What is going on with linked lists? (!)
50 * First recall the link list declaration from pmap_prot.h:
53 * struct pmap pml_map;
54 * struct pmaplist *pml_map;
57 * Compare that declaration with a corresponding xdr declaration that
58 * is (a) pointer-less, and (b) recursive:
60 * typedef union switch (bool_t) {
67 * case FALSE: struct {};
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.
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.
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!
87 xdr_pmaplist(xdrs, rp)
89 register struct pmaplist **rp;
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.
97 register int freeing = (xdrs->x_op == XDR_FREE);
98 register struct pmaplist **next = NULL;
101 more_elements = (bool_t)(*rp != NULL);
102 if (! xdr_bool(xdrs, &more_elements))
105 return (TRUE); /* we are done */
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 ...
112 next = &((*rp)->pml_next);
113 if (! xdr_reference(xdrs, (caddr_t *)rp,
114 (u_int)sizeof(struct pmaplist), xdr_pmap))
116 rp = (freeing) ? next : &((*rp)->pml_next);