Test-HashingSpeed.C

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// code taken more-or-less from Paul Hsieh's tests
 
#include "Hasher.H"
#include "int.H"
 
#include <stdio.h>
#include <time.h>
 
#ifndef CLOCKS_PER_SEC
# ifdef CLK_TCK
#  define CLOCKS_PER_SEC (CLK_TCK)
# endif
#endif
 
#undef mix
#undef rot
 
/*
-------------------------------------------------------------------------------
lookup3.c, by Bob Jenkins, May 2006, Public Domain.
 
These are functions for producing 32-bit hashes for hash table lookup.
hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
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's in
the public domain.  It has no warranty.
 
You probably want to use hashlittle().  hashlittle() and hashbig()
hash byte arrays.  hashlittle() is is faster than hashbig() on
little-endian machines.  Intel and AMD are little-endian machines.
On second thought, you probably want hashlittle2(), which is identical to
hashlittle() except it returns two 32-bit hashes for the price of one.
You could implement hashbig2() if you wanted but I haven't bothered here.
 
If you want to find a hash of, say, exactly 7 integers, do
  a = i1;  b = i2;  c = i3;
  mix(a,b,c);
  a += i4; b += i5; c += i6;
  mix(a,b,c);
  a += i7;
  final(a,b,c);
then use c as the hash value.  If you have a variable length array of
4-byte integers to hash, use hashword().  If you have a byte array (like
a character string), use hashlittle().  If you have several byte arrays, or
a mix of things, see the comments above hashlittle().
 
Why is this so big?  I read 12 bytes at a time into 3 4-byte integers,
then mix those integers.  This is fast (you can do a lot more thorough
mixing with 12*3 instructions on 3 integers than you can with 3 instructions
on 1 byte), but shoehorning those bytes into integers efficiently is messy.
-------------------------------------------------------------------------------
*/
 
#include <stdio.h>      /* defines printf for tests */
#include <time.h>       /* defines time_t for timings in the test */
#include <sys/param.h>  /* attempt to define endianness */
#ifdef linux
    #include <endian.h> /* attempt to define endianness */
#endif
 
/*
 * My best guess at if you are big-endian or little-endian.  This may
 * need adjustment.
 */
#if (defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && \
     __BYTE_ORDER == __LITTLE_ENDIAN) || \
    (defined(i386) || defined(__i386__) || defined(__i486__) || \
     defined(__i586__) || defined(__i686__) || defined(vax) || defined(MIPSEL))
# define HASH_LITTLE_ENDIAN 1
# define HASH_BIG_ENDIAN 0
#elif (defined(__BYTE_ORDER) && defined(__BIG_ENDIAN) && \
       __BYTE_ORDER == __BIG_ENDIAN) || \
      (defined(sparc) || defined(POWERPC) || defined(mc68000) || defined(sel))
# define HASH_LITTLE_ENDIAN 0
# define HASH_BIG_ENDIAN 1
#else
# define HASH_LITTLE_ENDIAN 0
# define HASH_BIG_ENDIAN 0
#endif
 
#define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
 
/*
-------------------------------------------------------------------------------
mix -- mix 3 32-bit values reversibly.
 
This is reversible, so any information in (a,b,c) before mix() is
still in (a,b,c) after mix().
 
If four pairs of (a,b,c) inputs are run through mix(), or through
mix() in reverse, there are at least 32 bits of the output that
are sometimes the same for one pair and different for another pair.
This was tested for:
* pairs that differed by one bit, by two bits, in any combination
  of top bits of (a,b,c), or in any combination of bottom bits of
  (a,b,c).
* "differ" is defined as +, -, ^, or ~^.  For + and -, I transformed
  the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
  is commonly produced by subtraction) look like a single 1-bit
  difference.
* the base values were pseudorandom, all zero but one bit set, or
  all zero plus a counter that starts at zero.
 
Some k values for my "a-=c; a^=rot(c,k); c+=b;" arrangement that
satisfy this are
    4  6  8 16 19  4
    9 15  3 18 27 15
   14  9  3  7 17  3
Well, "9 15 3 18 27 15" didn't quite get 32 bits diffing
for "differ" defined as + with a one-bit base and a two-bit delta.  I
used http://burtleburtle.net/bob/hash/avalanche.html to choose
the operations, constants, and arrangements of the variables.
 
This does not achieve avalanche.  There are input bits of (a,b,c)
that fail to affect some output bits of (a,b,c), especially of a.  The
most thoroughly mixed value is c, but it doesn't really even achieve
avalanche in c.
 
This allows some parallelism.  Read-after-writes are good at doubling
the number of bits affected, so the goal of mixing pulls in the opposite
direction as the goal of parallelism.  I did what I could.  Rotates
seem to cost as much as shifts on every machine I could lay my hands
on, and rotates are much kinder to the top and bottom bits, so I used
rotates.
-------------------------------------------------------------------------------
*/
#define mix(a,b,c) \
{ \
  a -= c;  a ^= rot(c, 4);  c += b; \
  b -= a;  b ^= rot(a, 6);  a += c; \
  c -= b;  c ^= rot(b, 8);  b += a; \
  a -= c;  a ^= rot(c,16);  c += b; \
  b -= a;  b ^= rot(a,19);  a += c; \
  c -= b;  c ^= rot(b, 4);  b += a; \
}
 
/*
-------------------------------------------------------------------------------
final -- final mixing of 3 32-bit values (a,b,c) into c
 
Pairs of (a,b,c) values differing in only a few bits will usually
produce values of c that look totally different.  This was tested for
* pairs that differed by one bit, by two bits, in any combination
  of top bits of (a,b,c), or in any combination of bottom bits of
  (a,b,c).
* "differ" is defined as +, -, ^, or ~^.  For + and -, I transformed
  the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
  is commonly produced by subtraction) look like a single 1-bit
  difference.
* the base values were pseudorandom, all zero but one bit set, or
  all zero plus a counter that starts at zero.
 
These constants passed:
 14 11 25 16 4 14 24
 12 14 25 16 4 14 24
and these came close:
  4  8 15 26 3 22 24
 10  8 15 26 3 22 24
 11  8 15 26 3 22 24
-------------------------------------------------------------------------------
*/
#define final(a,b,c) \
{ \
    c ^= b; c -= rot(b, 14); \
    a ^= c; a -= rot(c, 11); \
    b ^= a; b -= rot(a, 25); \
    c ^= b; c -= rot(b, 16); \
    a ^= c; a -= rot(c, 4);  \
    b ^= a; b -= rot(a, 14); \
    c ^= b; c -= rot(b, 24); \
}
 
/*
--------------------------------------------------------------------
 This works on all machines.  To be useful, it requires
 -- that the key be an array of uint32_t's, and
 -- that the length be the number of uint32_t's in the key
 
 The function hashword() is identical to hashlittle() on little-endian
 machines, and identical to hashbig() on big-endian machines,
 except that the length has to be measured in uint32_ts rather than in
 bytes.  hashlittle() is more complicated than hashword() only because
 hashlittle() has to dance around fitting the key bytes into registers.
--------------------------------------------------------------------
*/
uint32_t hashword(
const uint32_t *k,                   /* the key, an array of uint32_t values */
size_t          length,               /* the length of the key, in uint32_ts */
uint32_t        initval)         /* the previous hash, or an arbitrary value */
{
  uint32_t a,b,c;
 
  /* Set up the internal state */
  a = b = c = 0xdeadbeef + (((uint32_t)length)<<2) + initval;
 
  /*------------------------------------------------- handle most of the key */
  while (length > 3)
  {
    a += k[0];
    b += k[1];
    c += k[2];
    mix(a,b,c);
    length -= 3;
    k += 3;
  }
 
  /*------------------------------------------- handle the last 3 uint32_t's */
  switch(length)                     /* all the case statements fall through */
  {
  case 3 : c+=k[2];
  case 2 : b+=k[1];
  case 1 : a+=k[0];
    final(a,b,c);
  case 0:     /* case 0: nothing left to add */
    break;
  }
  /*------------------------------------------------------ report the result */
  return c;
}
 
 
/*
--------------------------------------------------------------------
hashword2() -- same as hashword(), but take two seeds and return two
32-bit values.  pc and pb must both be nonnull, and *pc and *pb must
both be initialized with seeds.  If you pass in (*pb)==0, the output
(*pc) will be the same as the return value from hashword().
--------------------------------------------------------------------
*/
void hashword2 (
const uint32_t *k,                   /* the key, an array of uint32_t values */
size_t          length,               /* the length of the key, in uint32_ts */
uint32_t       *pc,                      /* IN: seed OUT: primary hash value */
uint32_t       *pb)               /* IN: more seed OUT: secondary hash value */
{
  uint32_t a,b,c;
 
  /* Set up the internal state */
  a = b = c = 0xdeadbeef + ((uint32_t)(length<<2)) + *pc;
  c += *pb;
 
  /*------------------------------------------------- handle most of the key */
  while (length > 3)
  {
    a += k[0];
    b += k[1];
    c += k[2];
    mix(a,b,c);
    length -= 3;
    k += 3;
  }
 
  /*------------------------------------------- handle the last 3 uint32_t's */
  switch(length)                     /* all the case statements fall through */
  {
  case 3 : c+=k[2];
  case 2 : b+=k[1];
  case 1 : a+=k[0];
    final(a,b,c);
  case 0:     /* case 0: nothing left to add */
    break;
  }
  /*------------------------------------------------------ report the result */
  *pc=c; *pb=b;
}
 
 
/*
-------------------------------------------------------------------------------
hashlittle() -- hash a variable-length key into a 32-bit value
  k       : the key (the unaligned variable-length array of bytes)
  length  : the length of the key, counting by bytes
  initval : can be any 4-byte value
Returns a 32-bit value.  Every bit of the key affects every bit of
the return value.  Two keys differing by one or two bits will have
totally different hash values.
 
The best hash table sizes are powers of 2.  There is no need to do
mod a prime (mod is sooo slow!).  If you need less than 32 bits,
use a bitmask.  For example, if you need only 10 bits, do
  h = (h & hashmask(10));
In which case, the hash table should have hashsize(10) elements.
 
If you are hashing n strings (uint8_t **)k, do it like this:
  for (i=0, h=0; i<n; ++i) h = hashlittle( k[i], len[i], h);
 
By Bob Jenkins, 2006.  bob_jenkins@burtleburtle.net.  You may use this
code any way you wish, private, educational, or commercial.  It's free.
 
Use for hash table lookup, or anything where one collision in 2^^32 is
acceptable.  Do NOT use for cryptographic purposes.
-------------------------------------------------------------------------------
*/
 
uint32_t hashlittle( const void *key, size_t length, uint32_t initval)
{
  uint32_t a,b,c;                                          /* internal state */
  union { const void *ptr; size_t i; } u;     /* needed for Mac Powerbook G4 */
 
  /* Set up the internal state */
  a = b = c = 0xdeadbeef + ((uint32_t)length) + initval;
 
  u.ptr = key;
  if (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0)) {
    const uint32_t *k = (const uint32_t *)key;         /* read 32-bit chunks */
    const uint8_t  *k8;
 
    /*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
    while (length > 12)
    {
      a += k[0];
      b += k[1];
      c += k[2];
      mix(a,b,c);
      length -= 12;
      k += 3;
    }
 
    /*----------------------------- handle the last (probably partial) block */
 
    k8 = (const uint8_t *)k;
    switch(length)
    {
    case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
    case 11: c+=((uint32_t)k8[10])<<16;  /* fall through */
    case 10: c+=((uint32_t)k8[9])<<8;    /* fall through */
    case 9 : c+=k8[8];                   /* fall through */
    case 8 : b+=k[1]; a+=k[0]; break;
    case 7 : b+=((uint32_t)k8[6])<<16;   /* fall through */
    case 6 : b+=((uint32_t)k8[5])<<8;    /* fall through */
    case 5 : b+=k8[4];                   /* fall through */
    case 4 : a+=k[0]; break;
    case 3 : a+=((uint32_t)k8[2])<<16;   /* fall through */
    case 2 : a+=((uint32_t)k8[1])<<8;    /* fall through */
    case 1 : a+=k8[0]; break;
    case 0 : return c;
    }
 
  } else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
    const uint16_t *k = (const uint16_t *)key;         /* read 16-bit chunks */
    const uint8_t  *k8;
 
    /*--------------- all but last block: aligned reads and different mixing */
    while (length > 12)
    {
      a += k[0] + (((uint32_t)k[1])<<16);
      b += k[2] + (((uint32_t)k[3])<<16);
      c += k[4] + (((uint32_t)k[5])<<16);
      mix(a,b,c);
      length -= 12;
      k += 6;
    }
 
    /*----------------------------- handle the last (probably partial) block */
    k8 = (const uint8_t *)k;
    switch(length)
    {
    case 12: c+=k[4]+(((uint32_t)k[5])<<16);
             b+=k[2]+(((uint32_t)k[3])<<16);
             a+=k[0]+(((uint32_t)k[1])<<16);
             break;
    case 11: c+=((uint32_t)k8[10])<<16;     /* fall through */
    case 10: c+=k[4];
             b+=k[2]+(((uint32_t)k[3])<<16);
             a+=k[0]+(((uint32_t)k[1])<<16);
             break;
    case 9 : c+=k8[8];                      /* fall through */
    case 8 : b+=k[2]+(((uint32_t)k[3])<<16);
             a+=k[0]+(((uint32_t)k[1])<<16);
             break;
    case 7 : b+=((uint32_t)k8[6])<<16;      /* fall through */
    case 6 : b+=k[2];
             a+=k[0]+(((uint32_t)k[1])<<16);
             break;
    case 5 : b+=k8[4];                      /* fall through */
    case 4 : a+=k[0]+(((uint32_t)k[1])<<16);
             break;
    case 3 : a+=((uint32_t)k8[2])<<16;      /* fall through */
    case 2 : a+=k[0];
             break;
    case 1 : a+=k8[0];
             break;
    case 0 : return c;                     /* zero length requires no mixing */
    }
 
  } else {                        /* need to read the key one byte at a time */
    const uint8_t *k = (const uint8_t *)key;
 
    /*--------------- all but the last block: affect some 32 bits of (a,b,c) */
    while (length > 12)
    {
      a += k[0];
      a += ((uint32_t)k[1])<<8;
      a += ((uint32_t)k[2])<<16;
      a += ((uint32_t)k[3])<<24;
      b += k[4];
      b += ((uint32_t)k[5])<<8;
      b += ((uint32_t)k[6])<<16;
      b += ((uint32_t)k[7])<<24;
      c += k[8];
      c += ((uint32_t)k[9])<<8;
      c += ((uint32_t)k[10])<<16;
      c += ((uint32_t)k[11])<<24;
      mix(a,b,c);
      length -= 12;
      k += 12;
    }
 
    /*-------------------------------- last block: affect all 32 bits of (c) */
    switch(length)                   /* all the case statements fall through */
    {
    case 12: c+=((uint32_t)k[11])<<24;
    case 11: c+=((uint32_t)k[10])<<16;
    case 10: c+=((uint32_t)k[9])<<8;
    case 9 : c+=k[8];
 
    case 8 : b+=((uint32_t)k[7])<<24;
    case 7 : b+=((uint32_t)k[6])<<16;
    case 6 : b+=((uint32_t)k[5])<<8;
    case 5 : b+=k[4];
 
    case 4 : a+=((uint32_t)k[3])<<24;
    case 3 : a+=((uint32_t)k[2])<<16;
    case 2 : a+=((uint32_t)k[1])<<8;
    case 1 : a+=k[0];
             break;
 
    case 0 : return c;
    }
  }
 
  final(a,b,c);
  return c;
}
 
 
/*
 * hashlittle2: return 2 32-bit hash values
 *
 * This is identical to hashlittle(), except it returns two 32-bit hash
 * values instead of just one.  This is good enough for hash table
 * lookup with 2^^64 buckets, or if you want a second hash if you're not
 * happy with the first, or if you want a probably-unique 64-bit ID for
 * the key.  *pc is better mixed than *pb, so use *pc first.  If you want
 * a 64-bit value do something like "*pc + (((uint64_t)*pb)<<32)".
 */
void hashlittle2(
  const void *key,       /* the key to hash */
  size_t      length,    /* length of the key */
  uint32_t   *pc,        /* IN: primary initval, OUT: primary hash */
  uint32_t   *pb)        /* IN: secondary initval, OUT: secondary hash */
{
  uint32_t a,b,c;                                          /* internal state */
  union { const void *ptr; size_t i; } u;     /* needed for Mac Powerbook G4 */
 
  /* Set up the internal state */
  a = b = c = 0xdeadbeef + ((uint32_t)length) + *pc;
  c += *pb;
 
  u.ptr = key;
  if (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0)) {
    const uint32_t *k = (const uint32_t *)key;         /* read 32-bit chunks */
    const uint8_t  *k8;
 
    /*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
    while (length > 12)
    {
      a += k[0];
      b += k[1];
      c += k[2];
      mix(a,b,c);
      length -= 12;
      k += 3;
    }
 
    /*----------------------------- handle the last (probably partial) block */
 
    k8 = (const uint8_t *)k;
    switch(length)
    {
    case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
    case 11: c+=((uint32_t)k8[10])<<16;  /* fall through */
    case 10: c+=((uint32_t)k8[9])<<8;    /* fall through */
    case 9 : c+=k8[8];                   /* fall through */
    case 8 : b+=k[1]; a+=k[0]; break;
    case 7 : b+=((uint32_t)k8[6])<<16;   /* fall through */
    case 6 : b+=((uint32_t)k8[5])<<8;    /* fall through */
    case 5 : b+=k8[4];                   /* fall through */
    case 4 : a+=k[0]; break;
    case 3 : a+=((uint32_t)k8[2])<<16;   /* fall through */
    case 2 : a+=((uint32_t)k8[1])<<8;    /* fall through */
    case 1 : a+=k8[0]; break;
    case 0 : *pc=c; *pb=b; return;  /* zero length strings require no mixing */
    }
 
  } else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
    const uint16_t *k = (const uint16_t *)key;         /* read 16-bit chunks */
    const uint8_t  *k8;
 
    /*--------------- all but last block: aligned reads and different mixing */
    while (length > 12)
    {
      a += k[0] + (((uint32_t)k[1])<<16);
      b += k[2] + (((uint32_t)k[3])<<16);
      c += k[4] + (((uint32_t)k[5])<<16);
      mix(a,b,c);
      length -= 12;
      k += 6;
    }
 
    /*----------------------------- handle the last (probably partial) block */
    k8 = (const uint8_t *)k;
    switch(length)
    {
    case 12: c+=k[4]+(((uint32_t)k[5])<<16);
             b+=k[2]+(((uint32_t)k[3])<<16);
             a+=k[0]+(((uint32_t)k[1])<<16);
             break;
    case 11: c+=((uint32_t)k8[10])<<16;     /* fall through */
    case 10: c+=k[4];
             b+=k[2]+(((uint32_t)k[3])<<16);
             a+=k[0]+(((uint32_t)k[1])<<16);
             break;
    case 9 : c+=k8[8];                      /* fall through */
    case 8 : b+=k[2]+(((uint32_t)k[3])<<16);
             a+=k[0]+(((uint32_t)k[1])<<16);
             break;
    case 7 : b+=((uint32_t)k8[6])<<16;      /* fall through */
    case 6 : b+=k[2];
             a+=k[0]+(((uint32_t)k[1])<<16);
             break;
    case 5 : b+=k8[4];                      /* fall through */
    case 4 : a+=k[0]+(((uint32_t)k[1])<<16);
             break;
    case 3 : a+=((uint32_t)k8[2])<<16;      /* fall through */
    case 2 : a+=k[0];
             break;
    case 1 : a+=k8[0];
             break;
    case 0 : *pc=c; *pb=b; return;  /* zero length strings require no mixing */
    }
 
  } else {                        /* need to read the key one byte at a time */
    const uint8_t *k = (const uint8_t *)key;
 
    /*--------------- all but the last block: affect some 32 bits of (a,b,c) */
    while (length > 12)
    {
      a += k[0];
      a += ((uint32_t)k[1])<<8;
      a += ((uint32_t)k[2])<<16;
      a += ((uint32_t)k[3])<<24;
      b += k[4];
      b += ((uint32_t)k[5])<<8;
      b += ((uint32_t)k[6])<<16;
      b += ((uint32_t)k[7])<<24;
      c += k[8];
      c += ((uint32_t)k[9])<<8;
      c += ((uint32_t)k[10])<<16;
      c += ((uint32_t)k[11])<<24;
      mix(a,b,c);
      length -= 12;
      k += 12;
    }
 
    /*-------------------------------- last block: affect all 32 bits of (c) */
    switch(length)                   /* all the case statements fall through */
    {
    case 12: c+=((uint32_t)k[11])<<24;
    case 11: c+=((uint32_t)k[10])<<16;
    case 10: c+=((uint32_t)k[9])<<8;
    case 9 : c+=k[8];
    case 8 : b+=((uint32_t)k[7])<<24;
    case 7 : b+=((uint32_t)k[6])<<16;
    case 6 : b+=((uint32_t)k[5])<<8;
    case 5 : b+=k[4];
    case 4 : a+=((uint32_t)k[3])<<24;
    case 3 : a+=((uint32_t)k[2])<<16;
    case 2 : a+=((uint32_t)k[1])<<8;
    case 1 : a+=k[0];
             break;
    case 0 : *pc=c; *pb=b; return;  /* zero length strings require no mixing */
    }
  }
 
  final(a,b,c);
  *pc=c; *pb=b;
}
 
 
 
/*
 * hashbig():
 * This is the same as hashword() on big-endian machines.  It is different
 * from hashlittle() on all machines.  hashbig() takes advantage of
 * big-endian byte ordering.
 */
uint32_t hashbig( const void *key, size_t length, uint32_t initval)
{
  uint32_t a,b,c;
  union { const void *ptr; size_t i; } u; /* to cast key to (size_t) happily */
 
  /* Set up the internal state */
  a = b = c = 0xdeadbeef + ((uint32_t)length) + initval;
 
  u.ptr = key;
  if (HASH_BIG_ENDIAN && ((u.i & 0x3) == 0)) {
    const uint32_t *k = (const uint32_t *)key;         /* read 32-bit chunks */
    const uint8_t  *k8;
 
    /*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
    while (length > 12)
    {
      a += k[0];
      b += k[1];
      c += k[2];
      mix(a,b,c);
      length -= 12;
      k += 3;
    }
 
    /*----------------------------- handle the last (probably partial) block */
 
    k8 = (const uint8_t *)k;
    switch(length)                   /* all the case statements fall through */
    {
    case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
    case 11: c+=((uint32_t)k8[10])<<8;  /* fall through */
    case 10: c+=((uint32_t)k8[9])<<16;  /* fall through */
    case 9 : c+=((uint32_t)k8[8])<<24;  /* fall through */
    case 8 : b+=k[1]; a+=k[0]; break;
    case 7 : b+=((uint32_t)k8[6])<<8;   /* fall through */
    case 6 : b+=((uint32_t)k8[5])<<16;  /* fall through */
    case 5 : b+=((uint32_t)k8[4])<<24;  /* fall through */
    case 4 : a+=k[0]; break;
    case 3 : a+=((uint32_t)k8[2])<<8;   /* fall through */
    case 2 : a+=((uint32_t)k8[1])<<16;  /* fall through */
    case 1 : a+=((uint32_t)k8[0])<<24; break;
    case 0 : return c;
    }
 
  } else {                        /* need to read the key one byte at a time */
    const uint8_t *k = (const uint8_t *)key;
 
    /*--------------- all but the last block: affect some 32 bits of (a,b,c) */
    while (length > 12)
    {
      a += ((uint32_t)k[0])<<24;
      a += ((uint32_t)k[1])<<16;
      a += ((uint32_t)k[2])<<8;
      a += ((uint32_t)k[3]);
      b += ((uint32_t)k[4])<<24;
      b += ((uint32_t)k[5])<<16;
      b += ((uint32_t)k[6])<<8;
      b += ((uint32_t)k[7]);
      c += ((uint32_t)k[8])<<24;
      c += ((uint32_t)k[9])<<16;
      c += ((uint32_t)k[10])<<8;
      c += ((uint32_t)k[11]);
      mix(a,b,c);
      length -= 12;
      k += 12;
    }
 
    /*-------------------------------- last block: affect all 32 bits of (c) */
    switch(length)                   /* all the case statements fall through */
    {
    case 12: c+=k[11];
    case 11: c+=((uint32_t)k[10])<<8;
    case 10: c+=((uint32_t)k[9])<<16;
    case 9 : c+=((uint32_t)k[8])<<24;
    case 8 : b+=k[7];
    case 7 : b+=((uint32_t)k[6])<<8;
    case 6 : b+=((uint32_t)k[5])<<16;
    case 5 : b+=((uint32_t)k[4])<<24;
    case 4 : a+=k[3];
    case 3 : a+=((uint32_t)k[2])<<8;
    case 2 : a+=((uint32_t)k[1])<<16;
    case 1 : a+=((uint32_t)k[0])<<24;
             break;
    case 0 : return c;
    }
  }
 
  final(a,b,c);
  return c;
}
 
 
uint32_t hashLookup3Orig (const char * k, int length) {
    return hashlittle (k, length, 0);
}
 
uint32_t hashLookup3 (const char * k, int length) {
    return Foam::Hasher(k, length, 0);
}
 
 
 
/* ======================================================================== */
 
static uint32_t crc_16_table[16] = {
  0x0000, 0xCC01, 0xD801, 0x1400, 0xF001, 0x3C00, 0x2800, 0xE401,
  0xA001, 0x6C00, 0x7800, 0xB401, 0x5000, 0x9C01, 0x8801, 0x4400
};
 
/*
 *      This code was found at: http://wannabe.guru.org/alg/node191.html
 *  and still exists here: http://www.fearme.com/misc/alg/node191.html
 *
 *  this source code is based on Rex and Binstock which, in turn,
 *  acknowledges William James Hunt.
 *
 *      According to the site this CRC uses the polynomial x^16+x^5+x^2+1.
 *      Unfortunately, DOCSIS uses x^16+x^12+x^5+1.  D'oh!
 */
 
static uint32_t GetCRC16Update
(
    uint32_t start_crc,
    const char * data_stream,
    int length
) {
uint32_t crc = start_crc;
uint32_t r;
 
  /* while there is more data to process */
  while (length-- > 0) {
 
    /* compute checksum of lower four bits of *data_stream */
    r = crc_16_table[crc & 0xF];
    crc = (crc >> 4) & 0x0FFF;
    crc ^= r ^ crc_16_table[*data_stream & 0xF];
 
    /* now compute checksum of upper four bits of *data_stream */
    r = crc_16_table[crc & 0xF];
    crc = (crc >> 4) & 0x0FFF;
    crc ^= r ^ crc_16_table[(*data_stream >> 4) & 0xF];
 
    /* next... */
    data_stream++;
  }
 
  return crc;
}
 
uint32_t GetCRC16 (const char * data_stream, int length) {
        return GetCRC16Update (0, data_stream, length);
}
 
/* ======================================================================== */
 
static uint32_t crc_table[256];
 
/*  This code was found at:
 *  http://cell.onecall.net/cell-relay/publications/software/CRC/32bitCRC.c.html
 */
 
/*                                                                      */
/* crc32h.c -- package to compute 32-bit CRC one byte at a time using   */
/*             the high-bit first (Big-Endian) bit ordering convention  */
/*                                                                      */
/* Synopsis:                                                            */
/*  gen_crc_table() -- generates a 256-word table containing all CRC    */
/*                     remainders for every possible 8-bit byte.  It    */
/*                     must be executed (once) before any CRC updates.  */
/*                                                                      */
/*  unsigned update_crc(crc_accum, data_blk_ptr, data_blk_size)         */
/*           unsigned crc_accum; char *data_blk_ptr; int data_blk_size; */
/*           Returns the updated value of the CRC accumulator after     */
/*           processing each byte in the addressed block of data.       */
/*                                                                      */
/*  It is assumed that an unsigned long is at least 32 bits wide and    */
/*  that the predefined type char occupies one 8-bit byte of storage.   */
/*                                                                      */
/*  The generator polynomial used for this version of the package is    */
/*  x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x^1+x^0 */
/*  as specified in the Autodin/Ethernet/ADCCP protocol standards.      */
/*  Other degree 32 polynomials may be substituted by re-defining the   */
/*  symbol POLYNOMIAL below.  Lower degree polynomials must first be    */
/*  multiplied by an appropriate power of x.  The representation used   */
/*  is that the coefficient of x^0 is stored in the LSB of the 32-bit   */
/*  word and the coefficient of x^31 is stored in the most significant  */
/*  bit.  The CRC is to be appended to the data most significant byte   */
/*  first.  For those protocols in which bytes are transmitted MSB      */
/*  first and in the same order as they are encountered in the block    */
/*  this convention results in the CRC remainder being transmitted with */
/*  the coefficient of x^31 first and with that of x^0 last (just as    */
/*  would be done by a hardware shift register mechanization).          */
/*                                                                      */
/*  The table lookup technique was adapted from the algorithm described */
/*  by Avram Perez, Byte-wise CRC Calculations, IEEE Micro 3, 40 (1983).*/
 
/* generate the table of CRC remainders for all possible bytes */
 
#define CRC32POLYNOMIAL 0x04c11db7L
 
static void GenerateCRC32Table (void) {
int i, j;
uint32_t crc_accum;
 
    for ( i = 0;  i < 256;  i++ ) {
        crc_accum = ( (unsigned long) i << 24 );
        for ( j = 0;  j < 8;  j++ ) {
            if ( crc_accum & 0x80000000L ) {
                crc_accum = ( crc_accum << 1 ) ^ CRC32POLYNOMIAL;
            } else {
                crc_accum = ( crc_accum << 1 );
            }
        }
        crc_table[i] = crc_accum;
    }
    return;
}
 
/* update the CRC on the data block one byte at a time */
 
static uint32_t UpdateCRC32
(
    uint32_t crc_accum,
    const char *data_blk_ptr,
    int data_blk_size
) {
int j;
uint8_t i;
 
        for (j = 0; j < data_blk_size; j++) {
                i = (crc_accum >> 24) ^ *data_blk_ptr++;
                crc_accum = (crc_accum << 8) ^ crc_table[i];
        }
        return crc_accum;
}
 
uint32_t GetCRC32 (const char * data_stream, int length) {
        return UpdateCRC32 (0, data_stream, length);
}
 
/* ======================================================================== */
 
/* Performs two parallel CRC-32 on even and odd bytes of the input, then
   combines the two in a further CRC-32 calculation */
 
uint32_t GetCRC32PH (const char *data_blk_ptr, int data_blk_size) {
int j;
uint8_t i0, i1;
uint32_t crc_accum0 = 0, crc_accum1 = 0x23456789u;
 
        if (data_blk_size & 1) crc_accum0 ^= *data_blk_ptr++;
        for (j = 1; j < data_blk_size; j+=2) {
                i0 = ((crc_accum0 >> 24) ^ *data_blk_ptr++);
                i1 = ((crc_accum1 >> 24) ^ *data_blk_ptr++);
                crc_accum0 = (crc_accum0 << 8) ^ crc_table[i0];
                crc_accum1 = (crc_accum1 << 8) ^ crc_table[i1];
        }
        return crc_accum0 + crc_accum1;
}
 
/* ======================================================================== */
 
/* Fowler / Noll / Vo (FNV) Hash
 
   http://www.isthe.com/chongo/tech/comp/fnv/ */
 
uint32_t FNVHash (const char * data, int len) {
int i;
uint32_t hash;
 
        hash = 2166136261u;
        for (i=0; i < len; i++) {
                hash = (16777619u * hash) ^ data[i];
        }
        return hash;
}
 
/* ======================================================================== */
 
/*
 * http://burtleburtle.net/bob/hash/doobs.html
 */
 
uint32_t oneAtATimeHash (const char * s, int len) {
int32_t hash;
int i;
 
        for (hash = 0, i = 0; i < len; i++) {
                hash += s[i];
                hash += (hash << 10);
                hash ^= (hash >>  6);   /* Non-portable due to ANSI C */
        }
        hash += (hash <<  3);
        hash ^= (hash >> 11);           /* Non-portable due to ANSI C */
        hash += (hash << 15);
        return (uint32_t) hash;
}
 
/* ======================================================================== */
 
uint32_t oneAtATimeHashPH (const char * s, int len) {
int32_t hash0 = 0, hash1 = 0x23456789;
int i;
 
        if (len & 1) hash1 ^= *s++;
 
        for (i = 1; i < len; i+=2) {
                hash0 += *s++;
                hash1 += *s++;
                hash0 += (hash0 << 10);
                hash1 += (hash1 << 10);
                hash0 ^= (hash0 >>  6); /* Non-portable due to ANSI C */
                hash1 ^= (hash1 >>  6); /* Non-portable due to ANSI C */
        }
 
        hash0 += hash1;
 
        hash0 += (hash0 <<  3);
        hash0 ^= (hash0 >> 11);         /* Non-portable due to ANSI C */
        hash0 += (hash0 << 15);
        return (uint32_t) hash0;
}
 
/* ======================================================================== */
 
/* By Paul Hsieh (C) 2004, 2005.  Covered under the Paul Hsieh derivative
   license. See:
   http://www.azillionmonkeys.com/qed/weblicense.html for license details.
 
   http://www.azillionmonkeys.com/qed/hash.html */
 
#undef get16bits
#if 0
#if (defined(__GNUC__) && defined(__i386__)) || defined(__WATCOMC__) \
  || defined(_MSC_VER) || defined (__BORLANDC__) || defined (__TURBOC__)
#define get16bits(d) (*((const uint16_t *) (d)))
#endif
#endif
 
#if !defined (get16bits)
#define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
                       +(uint32_t)(((const uint8_t *)(d))[0]) )
#endif
 
uint32_t SuperFastHash (const char * data, int len)
{
    uint32_t hash = 0;
 
    if (len <= 0 || data == NULL) return 0;
 
    unsigned rem = len & 3;
    len >>= 2;
 
    /* Main loop */
    for (;len > 0; len--) {
        hash += get16bits(data);
        hash = (hash << 16) ^ ((get16bits(data+2) << 11) ^ hash);
        hash += hash >> 11;
        data += 2*sizeof(uint16_t);
    }
 
    /* Handle end cases */
    switch (rem) {
        case 3 :
            hash += get16bits(data);
            hash ^= hash << 16;
            hash ^= data[sizeof (uint16_t)] << 18;
            hash += hash >> 11;
            break;
 
        case 2 :
            hash += get16bits (data);
            hash ^= hash << 11;
            hash += hash >> 17;
            break;
 
        case 1 : hash += *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;
}
 
/* ======================================================================== */
 
/* A hashing function that I believe was created by either Chris Torek or
   Dan Bernstein */
 
uint32_t alphaNumHash (const char * s, int len) {
uint32_t h;
int i;
 
    for (h = 0, i = 0; i < len; i++) {
        h = (h << 5) + (h * 5) + (unsigned char) s[i];
    }
    return h;
}
 
uint32_t bernstein (const char * s, int len) {
uint32_t h;
int i;
 
    for (h = 0, i = 0; i < len; i++) {
        h = (h << 5) + h + (unsigned char) s[i];
    }
    return h;
}
 
 
// found somewhere in the 2nd addition
uint32_t stroustrup (const char * s, int len) {
    uint32_t h;
 
    for (int i=0; i < len; ++s, ++i)
    {
        h = (h << 1) ^ (unsigned char) s[i];
    }
 
    return h;
}
 
 
/* ======================================================================== */
 
typedef uint32_t (* hashFn) (const char * s, int len);
 
#define BUFF_SZ (128*2)
#define NTESTS 5000000
 
double test (hashFn hash) {
static char buff[BUFF_SZ];
clock_t c0, c1;
int32_t i;
 
        for (buff[0]=0, i=1; i < BUFF_SZ; i++) buff[i] = (char) (i + buff[i-1]);
 
        c0 = clock ();
        for (i=0; i < NTESTS; i++) hash (buff, BUFF_SZ);
        c1 = clock ();
        return (c1 - c0)*(1.0 / (double)CLOCKS_PER_SEC);
}
 
struct tagtest {
        double res;
        char * name;
        hashFn hash;
} tests[] = {
//      { 0.0, "CRC32\t\t", GetCRC32                  },
//      { 0.0, "oneAtATimeHash\t", oneAtATimeHash     },
//      { 0.0, "alphaNumHash\t",  alphaNumHash        },
        { 0.0, "FNVHash\t\t", FNVHash                 },
        { 0.0, "bernstein\t",  bernstein        },
        { 0.0, "stroustrup\t", stroustrup             },
        { 0.0, "hashLookup3\t", hashLookup3           },
        { 0.0, "hashLookup3Orig\t", hashLookup3Orig   },
        { 0.0, "SuperFastHash\t", SuperFastHash       },
        { 0.0, NULL, NULL                             }
};
 
int main () {
int i, j;
    GenerateCRC32Table ();
 
    for (j=0; tests[j].name != NULL; j++) {
        for (i=0; i < 3; i++) {
            double res = test (tests[j].hash);
            if (tests[j].res == 0.0 || tests[j].res > res) tests[j].res = res;
        }
        printf ("%s:%8.4fs\n", tests[j].name, tests[j].res);
    }
 
    return 0;
}