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28f540f4 RM |
1 | /* @(#)pmap_prot2.c 2.1 88/07/29 4.0 RPCSRC */ |
2 | /* | |
3 | * Sun RPC is a product of Sun Microsystems, Inc. and is provided for | |
4 | * unrestricted use provided that this legend is included on all tape | |
5 | * media and as a part of the software program in whole or part. Users | |
6 | * may copy or modify Sun RPC without charge, but are not authorized | |
7 | * to license or distribute it to anyone else except as part of a product or | |
8 | * program developed by the user. | |
e7fd8a39 | 9 | * |
28f540f4 RM |
10 | * SUN RPC IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING THE |
11 | * WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR | |
12 | * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE. | |
e7fd8a39 | 13 | * |
28f540f4 RM |
14 | * Sun RPC is provided with no support and without any obligation on the |
15 | * part of Sun Microsystems, Inc. to assist in its use, correction, | |
16 | * modification or enhancement. | |
e7fd8a39 | 17 | * |
28f540f4 RM |
18 | * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE |
19 | * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY SUN RPC | |
20 | * OR ANY PART THEREOF. | |
e7fd8a39 | 21 | * |
28f540f4 RM |
22 | * In no event will Sun Microsystems, Inc. be liable for any lost revenue |
23 | * or profits or other special, indirect and consequential damages, even if | |
24 | * Sun has been advised of the possibility of such damages. | |
e7fd8a39 | 25 | * |
28f540f4 RM |
26 | * Sun Microsystems, Inc. |
27 | * 2550 Garcia Avenue | |
28 | * Mountain View, California 94043 | |
29 | */ | |
30 | #if !defined(lint) && defined(SCCSIDS) | |
31 | static char sccsid[] = "@(#)pmap_prot2.c 1.3 87/08/11 Copyr 1984 Sun Micro"; | |
32 | #endif | |
33 | ||
34 | /* | |
35 | * pmap_prot2.c | |
36 | * Protocol for the local binder service, or pmap. | |
37 | * | |
38 | * Copyright (C) 1984, Sun Microsystems, Inc. | |
39 | */ | |
40 | ||
41 | #include <rpc/types.h> | |
42 | #include <rpc/xdr.h> | |
43 | #include <rpc/pmap_prot.h> | |
44 | ||
45 | ||
e7fd8a39 | 46 | /* |
28f540f4 RM |
47 | * What is going on with linked lists? (!) |
48 | * First recall the link list declaration from pmap_prot.h: | |
49 | * | |
50 | * struct pmaplist { | |
e7fd8a39 UD |
51 | * struct pmap pml_map; |
52 | * struct pmaplist *pml_map; | |
28f540f4 RM |
53 | * }; |
54 | * | |
e7fd8a39 | 55 | * Compare that declaration with a corresponding xdr declaration that |
28f540f4 RM |
56 | * is (a) pointer-less, and (b) recursive: |
57 | * | |
58 | * typedef union switch (bool_t) { | |
28f540f4 | 59 | * |
e7fd8a39 UD |
60 | * case TRUE: struct { |
61 | * struct pmap; | |
62 | * pmaplist_t foo; | |
63 | * }; | |
64 | * | |
65 | * case FALSE: struct {}; | |
28f540f4 RM |
66 | * } pmaplist_t; |
67 | * | |
68 | * Notice that the xdr declaration has no nxt pointer while | |
69 | * the C declaration has no bool_t variable. The bool_t can be | |
70 | * interpreted as ``more data follows me''; if FALSE then nothing | |
71 | * follows this bool_t; if TRUE then the bool_t is followed by | |
e7fd8a39 UD |
72 | * an actual struct pmap, and then (recursively) by the |
73 | * xdr union, pamplist_t. | |
28f540f4 RM |
74 | * |
75 | * This could be implemented via the xdr_union primitive, though this | |
76 | * would cause a one recursive call per element in the list. Rather than do | |
77 | * that we can ``unwind'' the recursion | |
78 | * into a while loop and do the union arms in-place. | |
79 | * | |
80 | * The head of the list is what the C programmer wishes to past around | |
81 | * the net, yet is the data that the pointer points to which is interesting; | |
82 | * this sounds like a job for xdr_reference! | |
83 | */ | |
84 | bool_t | |
e7fd8a39 UD |
85 | xdr_pmaplist (xdrs, rp) |
86 | XDR *xdrs; | |
87 | struct pmaplist **rp; | |
28f540f4 | 88 | { |
e7fd8a39 UD |
89 | /* |
90 | * more_elements is pre-computed in case the direction is | |
91 | * XDR_ENCODE or XDR_FREE. more_elements is overwritten by | |
92 | * xdr_bool when the direction is XDR_DECODE. | |
93 | */ | |
94 | bool_t more_elements; | |
95 | int freeing = (xdrs->x_op == XDR_FREE); | |
96 | struct pmaplist **next = NULL; | |
28f540f4 | 97 | |
e7fd8a39 UD |
98 | while (TRUE) |
99 | { | |
100 | more_elements = (bool_t) (*rp != NULL); | |
101 | if (!xdr_bool (xdrs, &more_elements)) | |
102 | return FALSE; | |
103 | if (!more_elements) | |
104 | return TRUE; /* we are done */ | |
105 | /* | |
106 | * the unfortunate side effect of non-recursion is that in | |
107 | * the case of freeing we must remember the next object | |
108 | * before we free the current object ... | |
109 | */ | |
110 | if (freeing) | |
111 | next = &((*rp)->pml_next); | |
112 | if (!xdr_reference (xdrs, (caddr_t *) rp, | |
113 | (u_int) sizeof (struct pmaplist), | |
114 | (xdrproc_t) xdr_pmap)) | |
115 | return FALSE; | |
116 | rp = freeing ? next : &((*rp)->pml_next); | |
117 | } | |
28f540f4 | 118 | } |