228 lines
6.2 KiB
Diff
228 lines
6.2 KiB
Diff
--- a/include/linux/jhash.h
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+++ b/include/linux/jhash.h
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@@ -3,80 +3,95 @@
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/* jhash.h: Jenkins hash support.
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*
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- * Copyright (C) 1996 Bob Jenkins (bob_jenkins@burtleburtle.net)
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+ * Copyright (C) 2006. Bob Jenkins (bob_jenkins@burtleburtle.net)
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*
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* http://burtleburtle.net/bob/hash/
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*
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* These are the credits from Bob's sources:
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*
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- * lookup2.c, by Bob Jenkins, December 1996, Public Domain.
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- * hash(), hash2(), hash3, and mix() are externally useful functions.
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- * Routines to test the hash are included if SELF_TEST is defined.
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- * You can use this free for any purpose. It has no warranty.
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+ * lookup3.c, by Bob Jenkins, May 2006, Public Domain.
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*
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- * Copyright (C) 2003 David S. Miller (davem@redhat.com)
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+ * These are functions for producing 32-bit hashes for hash table lookup.
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+ * hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
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+ * are externally useful functions. Routines to test the hash are included
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+ * if SELF_TEST is defined. You can use this free for any purpose. It's in
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+ * the public domain. It has no warranty.
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+ *
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+ * Copyright (C) 2009 Jozsef Kadlecsik (kadlec@blackhole.kfki.hu)
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*
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* I've modified Bob's hash to be useful in the Linux kernel, and
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- * any bugs present are surely my fault. -DaveM
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+ * any bugs present are my fault. Jozsef
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*/
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-/* NOTE: Arguments are modified. */
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-#define __jhash_mix(a, b, c) \
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+#define __rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
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+
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+/* __jhash_mix - mix 3 32-bit values reversibly. */
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+#define __jhash_mix(a,b,c) \
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+{ \
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+ a -= c; a ^= __rot(c, 4); c += b; \
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+ b -= a; b ^= __rot(a, 6); a += c; \
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+ c -= b; c ^= __rot(b, 8); b += a; \
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+ a -= c; a ^= __rot(c,16); c += b; \
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+ b -= a; b ^= __rot(a,19); a += c; \
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+ c -= b; c ^= __rot(b, 4); b += a; \
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+}
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+
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+/* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */
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+#define __jhash_final(a,b,c) \
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{ \
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- a -= b; a -= c; a ^= (c>>13); \
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- b -= c; b -= a; b ^= (a<<8); \
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- c -= a; c -= b; c ^= (b>>13); \
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- a -= b; a -= c; a ^= (c>>12); \
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- b -= c; b -= a; b ^= (a<<16); \
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- c -= a; c -= b; c ^= (b>>5); \
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- a -= b; a -= c; a ^= (c>>3); \
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- b -= c; b -= a; b ^= (a<<10); \
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- c -= a; c -= b; c ^= (b>>15); \
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+ c ^= b; c -= __rot(b,14); \
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+ a ^= c; a -= __rot(c,11); \
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+ b ^= a; b -= __rot(a,25); \
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+ c ^= b; c -= __rot(b,16); \
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+ a ^= c; a -= __rot(c,4); \
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+ b ^= a; b -= __rot(a,14); \
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+ c ^= b; c -= __rot(b,24); \
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}
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-/* The golden ration: an arbitrary value */
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-#define JHASH_GOLDEN_RATIO 0x9e3779b9
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+/* An arbitrary initial parameter */
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+#define JHASH_GOLDEN_RATIO 0xdeadbeef
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/* The most generic version, hashes an arbitrary sequence
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* of bytes. No alignment or length assumptions are made about
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- * the input key.
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+ * the input key. The result depends on endianness.
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*/
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static inline u32 jhash(const void *key, u32 length, u32 initval)
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{
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- u32 a, b, c, len;
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+ u32 a,b,c;
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const u8 *k = key;
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- len = length;
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- a = b = JHASH_GOLDEN_RATIO;
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- c = initval;
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-
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- while (len >= 12) {
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- a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24));
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- b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24));
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- c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24));
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-
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- __jhash_mix(a,b,c);
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+ /* Set up the internal state */
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+ a = b = c = JHASH_GOLDEN_RATIO + length + initval;
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+ /* all but the last block: affect some 32 bits of (a,b,c) */
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+ while (length > 12) {
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+ a += (k[0] + ((u32)k[1]<<8) + ((u32)k[2]<<16) + ((u32)k[3]<<24));
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+ b += (k[4] + ((u32)k[5]<<8) + ((u32)k[6]<<16) + ((u32)k[7]<<24));
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+ c += (k[8] + ((u32)k[9]<<8) + ((u32)k[10]<<16) + ((u32)k[11]<<24));
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+ __jhash_mix(a, b, c);
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+ length -= 12;
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k += 12;
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- len -= 12;
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}
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- c += length;
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- switch (len) {
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- case 11: c += ((u32)k[10]<<24);
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- case 10: c += ((u32)k[9]<<16);
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- case 9 : c += ((u32)k[8]<<8);
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- case 8 : b += ((u32)k[7]<<24);
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- case 7 : b += ((u32)k[6]<<16);
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- case 6 : b += ((u32)k[5]<<8);
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+ /* last block: affect all 32 bits of (c) */
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+ /* all the case statements fall through */
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+ switch (length) {
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+ case 12: c += (u32)k[11]<<24;
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+ case 11: c += (u32)k[10]<<16;
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+ case 10: c += (u32)k[9]<<8;
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+ case 9 : c += k[8];
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+ case 8 : b += (u32)k[7]<<24;
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+ case 7 : b += (u32)k[6]<<16;
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+ case 6 : b += (u32)k[5]<<8;
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case 5 : b += k[4];
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- case 4 : a += ((u32)k[3]<<24);
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- case 3 : a += ((u32)k[2]<<16);
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- case 2 : a += ((u32)k[1]<<8);
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+ case 4 : a += (u32)k[3]<<24;
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+ case 3 : a += (u32)k[2]<<16;
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+ case 2 : a += (u32)k[1]<<8;
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case 1 : a += k[0];
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- };
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-
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- __jhash_mix(a,b,c);
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+ __jhash_final(a, b, c);
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+ case 0 :
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+ break;
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+ }
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return c;
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}
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@@ -86,58 +101,57 @@ static inline u32 jhash(const void *key,
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*/
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static inline u32 jhash2(const u32 *k, u32 length, u32 initval)
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{
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- u32 a, b, c, len;
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+ u32 a, b, c;
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- a = b = JHASH_GOLDEN_RATIO;
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- c = initval;
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- len = length;
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+ /* Set up the internal state */
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+ a = b = c = JHASH_GOLDEN_RATIO + (length<<2) + initval;
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- while (len >= 3) {
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+ /* handle most of the key */
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+ while (length > 3) {
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a += k[0];
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b += k[1];
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c += k[2];
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__jhash_mix(a, b, c);
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- k += 3; len -= 3;
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+ length -= 3;
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+ k += 3;
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}
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- c += length * 4;
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-
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- switch (len) {
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- case 2 : b += k[1];
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- case 1 : a += k[0];
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- };
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-
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- __jhash_mix(a,b,c);
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+ /* handle the last 3 u32's */
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+ /* all the case statements fall through */
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+ switch (length) {
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+ case 3: c += k[2];
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+ case 2: b += k[1];
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+ case 1: a += k[0];
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+ __jhash_final(a, b, c);
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+ case 0: /* case 0: nothing left to add */
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+ break;
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+ }
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return c;
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}
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-
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/* A special ultra-optimized versions that knows they are hashing exactly
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* 3, 2 or 1 word(s).
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- *
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- * NOTE: In partilar the "c += length; __jhash_mix(a,b,c);" normally
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- * done at the end is not done here.
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*/
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static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval)
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{
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- a += JHASH_GOLDEN_RATIO;
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- b += JHASH_GOLDEN_RATIO;
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- c += initval;
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+ a += JHASH_GOLDEN_RATIO + initval;
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+ b += JHASH_GOLDEN_RATIO + initval;
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+ c += JHASH_GOLDEN_RATIO + initval;
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- __jhash_mix(a, b, c);
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+ __jhash_final(a, b, c);
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return c;
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}
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static inline u32 jhash_2words(u32 a, u32 b, u32 initval)
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{
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- return jhash_3words(a, b, 0, initval);
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+ return jhash_3words(0, a, b, initval);
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}
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static inline u32 jhash_1word(u32 a, u32 initval)
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{
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- return jhash_3words(a, 0, 0, initval);
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+ return jhash_3words(0, 0, a, initval);
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}
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#endif /* _LINUX_JHASH_H */
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