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authorRoland McGrath <roland@gnu.org>1995-02-18 01:27:10 +0000
committerRoland McGrath <roland@gnu.org>1995-02-18 01:27:10 +0000
commit28f540f45bbacd939bfd07f213bcad2bf730b1bf (patch)
tree15f07c4c43d635959c6afee96bde71fb1b3614ee /sunrpc/pmap_prot2.c
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+/* @(#)pmap_prot2.c 2.1 88/07/29 4.0 RPCSRC */
+/*
+ * Sun RPC is a product of Sun Microsystems, Inc. and is provided for
+ * unrestricted use provided that this legend is included on all tape
+ * media and as a part of the software program in whole or part. Users
+ * may copy or modify Sun RPC without charge, but are not authorized
+ * to license or distribute it to anyone else except as part of a product or
+ * program developed by the user.
+ *
+ * SUN RPC IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING THE
+ * WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
+ *
+ * Sun RPC is provided with no support and without any obligation on the
+ * part of Sun Microsystems, Inc. to assist in its use, correction,
+ * modification or enhancement.
+ *
+ * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
+ * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY SUN RPC
+ * OR ANY PART THEREOF.
+ *
+ * In no event will Sun Microsystems, Inc. be liable for any lost revenue
+ * or profits or other special, indirect and consequential damages, even if
+ * Sun has been advised of the possibility of such damages.
+ *
+ * Sun Microsystems, Inc.
+ * 2550 Garcia Avenue
+ * Mountain View, California 94043
+ */
+#if !defined(lint) && defined(SCCSIDS)
+static char sccsid[] = "@(#)pmap_prot2.c 1.3 87/08/11 Copyr 1984 Sun Micro";
+#endif
+
+/*
+ * pmap_prot2.c
+ * Protocol for the local binder service, or pmap.
+ *
+ * Copyright (C) 1984, Sun Microsystems, Inc.
+ */
+
+#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(xdrs, rp)
+ register XDR *xdrs;
+ register 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;
+ register int freeing = (xdrs->x_op == XDR_FREE);
+ register 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);
+ }
+}