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1 | /* ASN.1 Object identifier (OID) registry |
2 | * | |
3 | * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. | |
4 | * Written by David Howells (dhowells@redhat.com) | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or | |
7 | * modify it under the terms of the GNU General Public Licence | |
8 | * as published by the Free Software Foundation; either version | |
9 | * 2 of the Licence, or (at your option) any later version. | |
10 | */ | |
11 | ||
12 | #include <linux/export.h> | |
13 | #include <linux/oid_registry.h> | |
14 | #include "oid_registry_data.c" | |
15 | ||
16 | /** | |
17 | * look_up_OID - Find an OID registration for the specified data | |
18 | * @data: Binary representation of the OID | |
19 | * @datasize: Size of the binary representation | |
20 | */ | |
21 | enum OID look_up_OID(const void *data, size_t datasize) | |
22 | { | |
23 | const unsigned char *octets = data; | |
24 | enum OID oid; | |
25 | unsigned char xhash; | |
26 | unsigned i, j, k, hash; | |
27 | size_t len; | |
28 | ||
29 | /* Hash the OID data */ | |
30 | hash = datasize - 1; | |
31 | ||
32 | for (i = 0; i < datasize; i++) | |
33 | hash += octets[i] * 33; | |
34 | hash = (hash >> 24) ^ (hash >> 16) ^ (hash >> 8) ^ hash; | |
35 | hash &= 0xff; | |
36 | ||
37 | /* Binary search the OID registry. OIDs are stored in ascending order | |
38 | * of hash value then ascending order of size and then in ascending | |
39 | * order of reverse value. | |
40 | */ | |
41 | i = 0; | |
42 | k = OID__NR; | |
43 | while (i < k) { | |
44 | j = (i + k) / 2; | |
45 | ||
46 | xhash = oid_search_table[j].hash; | |
47 | if (xhash > hash) { | |
48 | k = j; | |
49 | continue; | |
50 | } | |
51 | if (xhash < hash) { | |
52 | i = j + 1; | |
53 | continue; | |
54 | } | |
55 | ||
56 | oid = oid_search_table[j].oid; | |
57 | len = oid_index[oid + 1] - oid_index[oid]; | |
58 | if (len > datasize) { | |
59 | k = j; | |
60 | continue; | |
61 | } | |
62 | if (len < datasize) { | |
63 | i = j + 1; | |
64 | continue; | |
65 | } | |
66 | ||
67 | /* Variation is most likely to be at the tail end of the | |
68 | * OID, so do the comparison in reverse. | |
69 | */ | |
70 | while (len > 0) { | |
71 | unsigned char a = oid_data[oid_index[oid] + --len]; | |
72 | unsigned char b = octets[len]; | |
73 | if (a > b) { | |
74 | k = j; | |
75 | goto next; | |
76 | } | |
77 | if (a < b) { | |
78 | i = j + 1; | |
79 | goto next; | |
80 | } | |
81 | } | |
82 | return oid; | |
83 | next: | |
84 | ; | |
85 | } | |
86 | ||
87 | return OID__NR; | |
88 | } | |
89 | EXPORT_SYMBOL_GPL(look_up_OID); |