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authorJesper Dangaard Brouer <brouer@redhat.com>2018-08-10 14:02:57 +0200
committerDaniel Borkmann <daniel@iogearbox.net>2018-08-10 16:07:49 +0200
commit11395686586bc9ca867b3f27501fd6c48244187a (patch)
tree4f53275a6ac49883aae2eb93e96425c6c8bd4f8b /samples/bpf
parenteb91e4d4db06adef06e7f50c02813c13c6ca5a5b (diff)
samples/bpf: add Paul Hsieh's (LGPL 2.1) hash function SuperFastHash
Adjusted function call API to take an initval. This allow the API user to set the initial value, as a seed. This could also be used for inputting the previous hash. Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'samples/bpf')
-rw-r--r--samples/bpf/hash_func01.h55
1 files changed, 55 insertions, 0 deletions
diff --git a/samples/bpf/hash_func01.h b/samples/bpf/hash_func01.h
new file mode 100644
index 000000000000..38255812e376
--- /dev/null
+++ b/samples/bpf/hash_func01.h
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: LGPL-2.1
+ *
+ * Based on Paul Hsieh's (LGPG 2.1) hash function
+ * From: http://www.azillionmonkeys.com/qed/hash.html
+ */
+
+#define get16bits(d) (*((const __u16 *) (d)))
+
+static __always_inline
+__u32 SuperFastHash (const char *data, int len, __u32 initval) {
+ __u32 hash = initval;
+ __u32 tmp;
+ int rem;
+
+ if (len <= 0 || data == NULL) return 0;
+
+ rem = len & 3;
+ len >>= 2;
+
+ /* Main loop */
+#pragma clang loop unroll(full)
+ for (;len > 0; len--) {
+ hash += get16bits (data);
+ tmp = (get16bits (data+2) << 11) ^ hash;
+ hash = (hash << 16) ^ tmp;
+ data += 2*sizeof (__u16);
+ hash += hash >> 11;
+ }
+
+ /* Handle end cases */
+ switch (rem) {
+ case 3: hash += get16bits (data);
+ hash ^= hash << 16;
+ hash ^= ((signed char)data[sizeof (__u16)]) << 18;
+ hash += hash >> 11;
+ break;
+ case 2: hash += get16bits (data);
+ hash ^= hash << 11;
+ hash += hash >> 17;
+ break;
+ case 1: hash += (signed char)*data;
+ hash ^= hash << 10;
+ hash += hash >> 1;
+ }
+
+ /* Force "avalanching" of final 127 bits */
+ hash ^= hash << 3;
+ hash += hash >> 5;
+ hash ^= hash << 4;
+ hash += hash >> 17;
+ hash ^= hash << 25;
+ hash += hash >> 6;
+
+ return hash;
+}