client: add a newline after terse disk util

[fio.git] / hash.h

diff --git a/hash.h b/hash.h
index acf17bb8e7f963b1ea5400a17d24819f319a8062..66dd3d6916ea5b1386948c2d2a661d8bce59abf9 100644 (file)
--- a/hash.h
+++ b/hash.h
@@ -1,5 +1,9 @@
 #ifndef _LINUX_HASH_H
 #define _LINUX_HASH_H
+
+#include <inttypes.h>
+#include "arch/arch.h"
+
 /* Fast hashing routine for a long.
    (C) 2002 William Lee Irwin III, IBM */
 
@@ -13,6 +17,7 @@
  * them can use shifts and additions instead of multiplications for
  * machines where multiplications are slow.
  */
+
 #if BITS_PER_LONG == 32
 /* 2^31 + 2^29 - 2^25 + 2^22 - 2^19 - 2^16 + 1 */
 #define GOLDEN_RATIO_PRIME 0x9e370001UL
@@ -23,13 +28,31 @@
 #error Define GOLDEN_RATIO_PRIME for your wordsize.
 #endif
 
-static inline unsigned long hash_long(unsigned long val, unsigned int bits)
+/*
+ * The above primes are actively bad for hashing, since they are
+ * too sparse. The 32-bit one is mostly ok, the 64-bit one causes
+ * real problems. Besides, the "prime" part is pointless for the
+ * multiplicative hash.
+ *
+ * Although a random odd number will do, it turns out that the golden
+ * ratio phi = (sqrt(5)-1)/2, or its negative, has particularly nice
+ * properties.
+ *
+ * These are the negative, (1 - phi) = (phi^2) = (3 - sqrt(5))/2.
+ * (See Knuth vol 3, section 6.4, exercise 9.)
+ */
+#define GOLDEN_RATIO_32 0x61C88647
+#define GOLDEN_RATIO_64 0x61C8864680B583EBull
+
+static inline unsigned long __hash_long(uint64_t val)
 {
-       unsigned long hash = val;
+       uint64_t hash = val;
 
 #if BITS_PER_LONG == 64
+       hash *= GOLDEN_RATIO_64;
+#else
        /*  Sigh, gcc can't optimise this alone like it does for 32 bits. */
-       unsigned long n = hash;
+       uint64_t n = hash;
        n <<= 18;
        hash -= n;
        n <<= 33;
@@ -42,17 +65,100 @@ static inline unsigned long hash_long(unsigned long val, unsigned int bits)
        hash += n;
        n <<= 2;
        hash += n;
-#else
-       /* On some cpus multiply is faster, on others gcc will do shifts */
-       hash *= GOLDEN_RATIO_PRIME;
 #endif
 
+       return hash;
+}
+
+static inline unsigned long hash_long(unsigned long val, unsigned int bits)
+{
        /* High bits are more random, so use them. */
-       return hash >> (BITS_PER_LONG - bits);
+       return __hash_long(val) >> (BITS_PER_LONG - bits);
+}
+
+static inline uint64_t __hash_u64(uint64_t val)
+{
+       return val * GOLDEN_RATIO_64;
 }
        
 static inline unsigned long hash_ptr(void *ptr, unsigned int bits)
 {
-       return hash_long((unsigned long)ptr, bits);
+       return hash_long((uintptr_t)ptr, bits);
 }
+
+/*
+ * Bob Jenkins jhash
+ */
+
+#define JHASH_INITVAL  GOLDEN_RATIO_32
+
+static inline uint32_t rol32(uint32_t word, uint32_t shift)
+{
+       return (word << shift) | (word >> (32 - shift));
+}
+
+/* __jhash_mix -- mix 3 32-bit values reversibly. */
+#define __jhash_mix(a, b, c)                   \
+{                                              \
+       a -= c;  a ^= rol32(c, 4);  c += b;     \
+       b -= a;  b ^= rol32(a, 6);  a += c;     \
+       c -= b;  c ^= rol32(b, 8);  b += a;     \
+       a -= c;  a ^= rol32(c, 16); c += b;     \
+       b -= a;  b ^= rol32(a, 19); a += c;     \
+       c -= b;  c ^= rol32(b, 4);  b += a;     \
+}
+
+/* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */
+#define __jhash_final(a, b, c)                 \
+{                                              \
+       c ^= b; c -= rol32(b, 14);              \
+       a ^= c; a -= rol32(c, 11);              \
+       b ^= a; b -= rol32(a, 25);              \
+       c ^= b; c -= rol32(b, 16);              \
+       a ^= c; a -= rol32(c, 4);               \
+       b ^= a; b -= rol32(a, 14);              \
+       c ^= b; c -= rol32(b, 24);              \
+}
+
+static inline uint32_t jhash(const void *key, uint32_t length, uint32_t initval)
+{
+       const uint8_t *k = key;
+       uint32_t a, b, c;
+
+       /* Set up the internal state */
+       a = b = c = JHASH_INITVAL + length + initval;
+
+       /* All but the last block: affect some 32 bits of (a,b,c) */
+       while (length > 12) {
+               a += *k;
+               b += *(k + 4);
+               c += *(k + 8);
+               __jhash_mix(a, b, c);
+               length -= 12;
+               k += 12;
+       }
+
+       /* Last block: affect all 32 bits of (c) */
+       /* All the case statements fall through */
+       switch (length) {
+       case 12: c += (uint32_t) k[11] << 24;   /* fall through */
+       case 11: c += (uint32_t) k[10] << 16;   /* fall through */
+       case 10: c += (uint32_t) k[9] << 8;     /* fall through */
+       case 9:  c += k[8];                     /* fall through */
+       case 8:  b += (uint32_t) k[7] << 24;    /* fall through */
+       case 7:  b += (uint32_t) k[6] << 16;    /* fall through */
+       case 6:  b += (uint32_t) k[5] << 8;     /* fall through */
+       case 5:  b += k[4];                     /* fall through */
+       case 4:  a += (uint32_t) k[3] << 24;    /* fall through */
+       case 3:  a += (uint32_t) k[2] << 16;    /* fall through */
+       case 2:  a += (uint32_t) k[1] << 8;     /* fall through */
+       case 1:  a += k[0];
+                __jhash_final(a, b, c);
+       case 0: /* Nothing left to add */
+               break;
+       }
+
+       return c;
+}
+
 #endif /* _LINUX_HASH_H */