1 | /* |
2 | * pmap_prot2.c |
3 | * Protocol for the local binder service, or pmap. |
4 | * |
5 | * Copyright (c) 2010, Oracle America, Inc. |
6 | * |
7 | * Redistribution and use in source and binary forms, with or without |
8 | * modification, are permitted provided that the following conditions are |
9 | * met: |
10 | * |
11 | * * Redistributions of source code must retain the above copyright |
12 | * notice, this list of conditions and the following disclaimer. |
13 | * * Redistributions in binary form must reproduce the above |
14 | * copyright notice, this list of conditions and the following |
15 | * disclaimer in the documentation and/or other materials |
16 | * provided with the distribution. |
17 | * * Neither the name of the "Oracle America, Inc." nor the names of its |
18 | * contributors may be used to endorse or promote products derived |
19 | * from this software without specific prior written permission. |
20 | * |
21 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
22 | * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
23 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
24 | * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
25 | * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, |
26 | * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
27 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE |
28 | * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
29 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
30 | * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING |
31 | * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
32 | * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
33 | */ |
34 | |
35 | #include <rpc/types.h> |
36 | #include <rpc/xdr.h> |
37 | #include <rpc/pmap_prot.h> |
38 | #include <shlib-compat.h> |
39 | |
40 | |
41 | /* |
42 | * What is going on with linked lists? (!) |
43 | * First recall the link list declaration from pmap_prot.h: |
44 | * |
45 | * struct pmaplist { |
46 | * struct pmap pml_map; |
47 | * struct pmaplist *pml_map; |
48 | * }; |
49 | * |
50 | * Compare that declaration with a corresponding xdr declaration that |
51 | * is (a) pointer-less, and (b) recursive: |
52 | * |
53 | * typedef union switch (bool_t) { |
54 | * |
55 | * case TRUE: struct { |
56 | * struct pmap; |
57 | * pmaplist_t foo; |
58 | * }; |
59 | * |
60 | * case FALSE: struct {}; |
61 | * } pmaplist_t; |
62 | * |
63 | * Notice that the xdr declaration has no nxt pointer while |
64 | * the C declaration has no bool_t variable. The bool_t can be |
65 | * interpreted as ``more data follows me''; if FALSE then nothing |
66 | * follows this bool_t; if TRUE then the bool_t is followed by |
67 | * an actual struct pmap, and then (recursively) by the |
68 | * xdr union, pamplist_t. |
69 | * |
70 | * This could be implemented via the xdr_union primitive, though this |
71 | * would cause a one recursive call per element in the list. Rather than do |
72 | * that we can ``unwind'' the recursion |
73 | * into a while loop and do the union arms in-place. |
74 | * |
75 | * The head of the list is what the C programmer wishes to past around |
76 | * the net, yet is the data that the pointer points to which is interesting; |
77 | * this sounds like a job for xdr_reference! |
78 | */ |
79 | bool_t |
80 | xdr_pmaplist (XDR *xdrs, struct pmaplist **rp) |
81 | { |
82 | /* |
83 | * more_elements is pre-computed in case the direction is |
84 | * XDR_ENCODE or XDR_FREE. more_elements is overwritten by |
85 | * xdr_bool when the direction is XDR_DECODE. |
86 | */ |
87 | bool_t more_elements; |
88 | int freeing = (xdrs->x_op == XDR_FREE); |
89 | struct pmaplist *next = NULL; |
90 | |
91 | while (TRUE) |
92 | { |
93 | more_elements = (bool_t) (*rp != NULL); |
94 | if (!xdr_bool (xdrs, &more_elements)) |
95 | return FALSE; |
96 | if (!more_elements) |
97 | return TRUE; /* we are done */ |
98 | /* |
99 | * the unfortunate side effect of non-recursion is that in |
100 | * the case of freeing we must remember the next object |
101 | * before we free the current object ... |
102 | */ |
103 | if (freeing) |
104 | next = (*rp)->pml_next; |
105 | if (!xdr_reference (xdrs, (caddr_t *) rp, |
106 | (u_int) sizeof (struct pmaplist), |
107 | (xdrproc_t) xdr_pmap)) |
108 | return FALSE; |
109 | rp = freeing ? &next : &((*rp)->pml_next); |
110 | } |
111 | } |
112 | libc_hidden_nolink_sunrpc (xdr_pmaplist, GLIBC_2_0) |
113 | |