90 строки
1.9 KiB
C
90 строки
1.9 KiB
C
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/* ASN.1 Object identifier (OID) registry
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*
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* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#include <linux/export.h>
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#include <linux/oid_registry.h>
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#include "oid_registry_data.c"
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/**
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* look_up_OID - Find an OID registration for the specified data
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* @data: Binary representation of the OID
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* @datasize: Size of the binary representation
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*/
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enum OID look_up_OID(const void *data, size_t datasize)
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{
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const unsigned char *octets = data;
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enum OID oid;
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unsigned char xhash;
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unsigned i, j, k, hash;
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size_t len;
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/* Hash the OID data */
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hash = datasize - 1;
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for (i = 0; i < datasize; i++)
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hash += octets[i] * 33;
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hash = (hash >> 24) ^ (hash >> 16) ^ (hash >> 8) ^ hash;
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hash &= 0xff;
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/* Binary search the OID registry. OIDs are stored in ascending order
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* of hash value then ascending order of size and then in ascending
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* order of reverse value.
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*/
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i = 0;
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k = OID__NR;
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while (i < k) {
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j = (i + k) / 2;
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xhash = oid_search_table[j].hash;
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if (xhash > hash) {
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k = j;
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continue;
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}
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if (xhash < hash) {
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i = j + 1;
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continue;
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}
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oid = oid_search_table[j].oid;
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len = oid_index[oid + 1] - oid_index[oid];
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if (len > datasize) {
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k = j;
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continue;
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}
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if (len < datasize) {
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i = j + 1;
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continue;
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}
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/* Variation is most likely to be at the tail end of the
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* OID, so do the comparison in reverse.
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*/
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while (len > 0) {
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unsigned char a = oid_data[oid_index[oid] + --len];
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unsigned char b = octets[len];
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if (a > b) {
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k = j;
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goto next;
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}
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if (a < b) {
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i = j + 1;
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goto next;
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}
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}
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return oid;
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next:
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;
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}
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return OID__NR;
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}
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EXPORT_SYMBOL_GPL(look_up_OID);
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