X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu%2Fjhash.h;fp=urcu%2Fjhash.h;h=27b9f7f4a20ac133aeadbcb6e5af36a4cd707753;hp=0000000000000000000000000000000000000000;hb=674f7a6983f888438c36f8fba179db1a5349d3e9;hpb=bb698e267fb01c1ed4073d83cfa8d935539ef52d

diff --git a/urcu/jhash.h b/urcu/jhash.h
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+#ifndef _KCOMPAT_JHASH_H
+#define _KCOMPAT_JHASH_H
+
+/* jhash.h: Jenkins hash support.
+ *
+ * Copyright (C) 1996 Bob Jenkins (bob_jenkins@burtleburtle.net)
+ *
+ * http://burtleburtle.net/bob/hash/
+ *
+ * These are the credits from Bob's sources:
+ *
+ * lookup2.c, by Bob Jenkins, December 1996, Public Domain.
+ * hash(), hash2(), hash3, and mix() are externally useful functions.
+ * Routines to test the hash are included if SELF_TEST is defined.
+ * You can use this free for any purpose.  It has no warranty.
+ *
+ * Copyright (C) 2003 David S. Miller (davem@redhat.com)
+ *
+ * I've modified Bob's hash to be useful in the Linux kernel, and
+ * any bugs present are surely my fault.  -DaveM
+ */
+
+#include <stdint.h>
+
+typedef uint32_t u32;
+
+/* NOTE: Arguments are modified. */
+#define __jhash_mix(a, b, c) \
+{ \
+  a -= b; a -= c; a ^= (c>>13); \
+  b -= c; b -= a; b ^= (a<<8); \
+  c -= a; c -= b; c ^= (b>>13); \
+  a -= b; a -= c; a ^= (c>>12);  \
+  b -= c; b -= a; b ^= (a<<16); \
+  c -= a; c -= b; c ^= (b>>5); \
+  a -= b; a -= c; a ^= (c>>3);  \
+  b -= c; b -= a; b ^= (a<<10); \
+  c -= a; c -= b; c ^= (b>>15); \
+}
+
+/* The golden ration: an arbitrary value */
+#define JHASH_GOLDEN_RATIO	0x9e3779b9
+
+/* The most generic version, hashes an arbitrary sequence
+ * of bytes.  No alignment or length assumptions are made about
+ * the input key.
+ */
+static inline u32 jhash(const void *key, u32 length, u32 initval)
+{
+	u32 a, b, c, len;
+	const u8 *k = key;
+
+	len = length;
+	a = b = JHASH_GOLDEN_RATIO;
+	c = initval;
+
+	while (len >= 12) {
+		a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24));
+		b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24));
+		c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24));
+
+		__jhash_mix(a,b,c);
+
+		k += 12;
+		len -= 12;
+	}
+
+	c += length;
+	switch (len) {
+	case 11: c += ((u32)k[10]<<24);
+	case 10: c += ((u32)k[9]<<16);
+	case 9 : c += ((u32)k[8]<<8);
+	case 8 : b += ((u32)k[7]<<24);
+	case 7 : b += ((u32)k[6]<<16);
+	case 6 : b += ((u32)k[5]<<8);
+	case 5 : b += k[4];
+	case 4 : a += ((u32)k[3]<<24);
+	case 3 : a += ((u32)k[2]<<16);
+	case 2 : a += ((u32)k[1]<<8);
+	case 1 : a += k[0];
+	};
+
+	__jhash_mix(a,b,c);
+
+	return c;
+}
+
+#endif /* _KCOMPAT_JHASH_H */