Hash

//
RS Hash Function

unsigned
int RSHash(char *str)

{

  unsigned
int b = 378551;

  unsigned
int a = 63689;

  unsigned
int hash = 0;

  while
(*str)

  {

    hash
= hash * a + (*str++);

    a
*= b;

  }

  return
(hash & 0x7FFFFFFF);

}

//
JS Hash Function

unsigned
int JSHash(char *str)

{

  unsigned
int hash = 1315423911;

  while
(*str)

  {

    hash
^= ((hash << 5) + (*str++) + (hash >> 2));

  }

  return
(hash & 0x7FFFFFFF);

}

//
P. J. Weinberger Hash Function

unsigned
int PJWHash(char *str)

{

  unsigned
int BitsInUnignedInt
= (unsigned int)(sizeof(unsigned
int) * 8);

  unsigned
int ThreeQuarters = (unsigned
int)((BitsInUnignedInt
* 3) / 4);

  unsigned
int OneEighth = (unsigned
int)(BitsInUnignedInt
/ 8);

  unsigned
int HighBits = (unsigned
int)(0xFFFFFFFF) <<
(BitsInUnignedInt - OneEighth);

  unsigned
int hash = 0;

  unsigned
int test = 0;

  while
(*str)

  {

    hash
= (hash << OneEighth) + (*str++);

    if
((test = hash & HighBits) != 0)

    {

      hash
= ((hash ^ (test >> ThreeQuarters)) & (~HighBits));

    }

  }

  return
(hash & 0x7FFFFFFF);

}

//
ELF Hash Function

unsigned
int ELFHash(char
*str)

{

  unsigned
int hash = 0;

  unsigned
int x = 0;

  while
(*str)

  {

    hash
= (hash << 4) + (*str++);

    if
((x = hash & 0xF0000000L) != 0)

    {

      hash
^= (x >> 24);

      hash
&= ~x;

    }

  }

  return
(hash & 0x7FFFFFFF);

}

//
BKDR Hash Function

unsigned
int BKDRHash(char
*str)

{

  unsigned
int seed = 131; //
31 131 1313 13131 131313 etc..

  unsigned
int hash = 0;

  while
(*str)

  {

    hash
= hash * seed + (*str++);

  }

  return
(hash & 0x7FFFFFFF);

}

//
SDBM Hash Function

unsigned
int SDBMHash(char
*str)

{

  unsigned
int hash = 0;

  while
(*str)

  {

    hash
= (*str++) + (hash << 6) + (hash << 16) - hash;

  }

  return
(hash & 0x7FFFFFFF);

}

//
DJB Hash Function

unsigned
int DJBHash(char
*str)

{

  unsigned
int hash = 5381;

  while
(*str)

  {

    hash
+= (hash << 5) + (*str++);

  }

  return
(hash & 0x7FFFFFFF);

}

//
AP Hash Function

unsigned
int APHash(char
*str)

{

  unsigned
int hash = 0;

  int
i;

  for
(i=0; *str; i++)

  {

    if
((i & 1) == 0)

    {

      hash
^= ((hash << 7) ^ (*str++) ^ (hash >> 3));

    }

    else

    {

      hash
^= (~((hash << 11) ^ (*str++) ^ (hash >> 5)));

    }

  }

  return
(hash & 0x7FFFFFFF);

}