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-rw-r--r--lib/oid_registry.c89
1 files changed, 89 insertions, 0 deletions
diff --git a/lib/oid_registry.c b/lib/oid_registry.c
new file mode 100644
index 000000000000..33cfd171f627
--- /dev/null
+++ b/lib/oid_registry.c
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+/* ASN.1 Object identifier (OID) registry
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/export.h>
+#include <linux/oid_registry.h>
+#include "oid_registry_data.c"
+
+/**
+ * look_up_OID - Find an OID registration for the specified data
+ * @data: Binary representation of the OID
+ * @datasize: Size of the binary representation
+ */
+enum OID look_up_OID(const void *data, size_t datasize)
+{
+ const unsigned char *octets = data;
+ enum OID oid;
+ unsigned char xhash;
+ unsigned i, j, k, hash;
+ size_t len;
+
+ /* Hash the OID data */
+ hash = datasize - 1;
+
+ for (i = 0; i < datasize; i++)
+ hash += octets[i] * 33;
+ hash = (hash >> 24) ^ (hash >> 16) ^ (hash >> 8) ^ hash;
+ hash &= 0xff;
+
+ /* Binary search the OID registry. OIDs are stored in ascending order
+ * of hash value then ascending order of size and then in ascending
+ * order of reverse value.
+ */
+ i = 0;
+ k = OID__NR;
+ while (i < k) {
+ j = (i + k) / 2;
+
+ xhash = oid_search_table[j].hash;
+ if (xhash > hash) {
+ k = j;
+ continue;
+ }
+ if (xhash < hash) {
+ i = j + 1;
+ continue;
+ }
+
+ oid = oid_search_table[j].oid;
+ len = oid_index[oid + 1] - oid_index[oid];
+ if (len > datasize) {
+ k = j;
+ continue;
+ }
+ if (len < datasize) {
+ i = j + 1;
+ continue;
+ }
+
+ /* Variation is most likely to be at the tail end of the
+ * OID, so do the comparison in reverse.
+ */
+ while (len > 0) {
+ unsigned char a = oid_data[oid_index[oid] + --len];
+ unsigned char b = octets[len];
+ if (a > b) {
+ k = j;
+ goto next;
+ }
+ if (a < b) {
+ i = j + 1;
+ goto next;
+ }
+ }
+ return oid;
+ next:
+ ;
+ }
+
+ return OID__NR;
+}
+EXPORT_SYMBOL_GPL(look_up_OID);