unsigned int RSHash(char* str, unsigned int len)   
{   
   unsigned int b    = 378551;   
   unsigned int a    = 63689;   
   unsigned int hash = 0;   
   unsigned int i    = 0;   
   for(i = 0; i < len; str++, i++)   
   {   
      hash = hash * a + (*str);   
      a    = a * b;   
   }   
   return hash;   
}   
/* End Of RS Hash Function */  
  
unsigned int JSHash(char* str, unsigned int len)   
{   
   unsigned int hash = 1315423911;   
   unsigned int i    = 0;   
   for(i = 0; i < len; str++, i++)   
   {   
      hash ^= ((hash << 5) + (*str) + (hash >> 2));   
   }   
   return hash;   
}   
/* End Of JS Hash Function */  
  
unsigned int PJWHash(char* str, unsigned int len)   
{   
   const unsigned int BitsInUnsignedInt = (unsigned int)(sizeof(unsigned int) * 8);   
   const unsigned int ThreeQuarters     = (unsigned int)((BitsInUnsignedInt  * 3) / 4);   
   const unsigned int OneEighth         = (unsigned int)(BitsInUnsignedInt / 8);   
   const unsigned int HighBits          = (unsigned int)(0xFFFFFFFF) << (BitsInUnsignedInt - OneEighth);   
   unsigned int hash              = 0;   
   unsigned int test              = 0;   
   unsigned int i                 = 0;   
   for(i = 0; i < len; str++, i++)   
   {   
      hash = (hash << OneEighth) + (*str);   
      if((test = hash & HighBits)  != 0)   
      {   
         hash = (( hash ^ (test >> ThreeQuarters)) & (~HighBits));   
      }   
   }   
   return hash;   
}   
/* End Of  P. J. Weinberger Hash Function */  
  
unsigned int ELFHash(char* str, unsigned int len)   
{   
   unsigned int hash = 0;   
   unsigned int x    = 0;   
   unsigned int i    = 0;   
   for(i = 0; i < len; str++, i++)   
   {   
      hash = (hash << 4) + (*str);   
      if((x = hash & 0xF0000000L) != 0)   
      {   
         hash ^= (x >> 24);   
      }   
      hash &= ~x;   
   }   
   return hash;   
}   
/* End Of ELF Hash Function */  
  
unsigned int BKDRHash(char* str, unsigned int len)   
{   
   unsigned int seed = 131; /* 31 131 1313 13131 131313 etc.. */  
   unsigned int hash = 0;   
   unsigned int i    = 0;   
   for(i = 0; i < len; str++, i++)   
   {   
      hash = (hash * seed) + (*str);   
   }   
   return hash;   
}   
/* End Of BKDR Hash Function */  
  
unsigned int SDBMHash(char* str, unsigned int len)   
{   
   unsigned int hash = 0;   
   unsigned int i    = 0;   
   for(i = 0; i < len; str++, i++)   
   {   
      hash = (*str) + (hash << 6) + (hash << 16) - hash;   
   }   
   return hash;   
}   
/* End Of SDBM Hash Function */  
  
unsigned int DJBHash(char* str, unsigned int len)   
{   
   unsigned int hash = 5381;   
   unsigned int i    = 0;   
   for(i = 0; i < len; str++, i++)   
   {   
      hash = ((hash << 5) + hash) + (*str);   
   }   
   return hash;   
}   
/* End Of DJB Hash Function */  
  
unsigned int DEKHash(char* str, unsigned int len)   
{   
   unsigned int hash = len;   
   unsigned int i    = 0;   
   for(i = 0; i < len; str++, i++)   
   {   
      hash = ((hash << 5) ^ (hash >> 27)) ^ (*str);   
   }   
   return hash;   
}   
/* End Of DEK Hash Function */  
  
unsigned int BPHash(char* str, unsigned int len)   
{   
   unsigned int hash = 0;   
   unsigned int i    = 0;   
   for(i = 0; i < len; str++, i++)   
   {   
      hash = hash << 7 ^ (*str);   
   }   
   return hash;   
}   
/* End Of BP Hash Function */  
  
unsigned int FNVHash(char* str, unsigned int len)   
{   
   const unsigned int fnv_prime = 0x811C9DC5;   
   unsigned int hash      = 0;   
   unsigned int i         = 0;   
   for(i = 0; i < len; str++, i++)   
   {   
      hash *= fnv_prime;   
      hash ^= (*str);   
   }   
   return hash;   
}   
/* End Of FNV Hash Function */  
  
unsigned int APHash(char* str, unsigned int len)   
{   
   unsigned int hash = 0xAAAAAAAA;   
   unsigned int i    = 0;   
   for(i = 0; i < len; str++, i++)   
   {   
      hash ^= ((i & 1) == 0) ? (  (hash <<  7) ^ (*str) * (hash >> 3)) :   
                               (~((hash << 11) + (*str) ^ (hash >> 5)));   
   }   
   return hash;   
}   
/* End Of AP Hash Function */ 
 

-------------------------------------------------------------------------------------------------------------------------------------------------------------

幾種經典的Hash演算法的實現(原始碼)

●PHP中出現的字串Hash函式

static unsigned long hashpjw(char *arKey, unsigned int nKeyLength)
{
unsigned long h = 0, g;
char *arEnd=arKey+nKeyLength; 

while (arKey < arEnd) {
h = (h << 4) + *arKey++;
if ((g = (h & 0xF0000000))) {
h = h ^ (g >> 24);
h = h ^ g;
}
}
return h;
}
 

●OpenSSL中出現的字串Hash函式

unsigned long lh_strhash(char *str)
{
int i,l;
unsigned long ret=0;
unsigned short *s; 

if (str == NULL) return(0);
l=(strlen(str)+1)/2;
s=(unsigned short *)str; 

for (i=0; i
ret^=(s[i]<<(i&0x0f));
return(ret);
} 

/* The following hash seems to work very well on normal text strings 
* no collisions on /usr/dict/words and it distributes on %2^n quite 
* well, not as good as MD5, but still good. 
*/
unsigned long lh_strhash(const char *c)
{
unsigned long ret=0;
long n;
unsigned long v;
int r; 

if ((c == NULL) || (*c == '\0'))
return(ret);
/*
unsigned char b[16]; 
MD5(c,strlen(c),b); 
return(b[0]|(b[1]<<8)|(b[2]<<16)|(b[3]<<24)); 
*/ 

n=0x100;
while (*c)
{
v=n|(*c);
n+=0x100;
r= (int)((v>>2)^v)&0x0f;
ret=(ret(32-r));
ret&=0xFFFFFFFFL;
ret^=v*v;
c++;
} 

return((ret>>16)^ret);
}
 

●MySql中出現的字串Hash函式

#ifndef NEW_HASH_FUNCTION 

/* Calc hashvalue for a key */
static uint calc_hashnr(const byte *key,uint length)
{
register uint nr=1, nr2=4; 

while (length--)
{
nr^= (((nr & 63)+nr2)*((uint) (uchar) *key++))+ (nr << 8);
nr2+=3;
} 

return((uint) nr);
} 

/* Calc hashvalue for a key, case indepenently */
static uint calc_hashnr_caseup(const byte *key,uint length)
{
register uint nr=1, nr2=4; 

while (length--)
{
nr^= (((nr & 63)+nr2)*((uint) (uchar) toupper(*key++)))+ (nr << 8);
nr2+=3;
} 

return((uint) nr);
}
#else
/* 
* Fowler/Noll/Vo hash 
* 
* The basis of the hash algorithm was taken from an idea sent by email to the 
* IEEE Posix P1003.2 mailing list from Phong Vo ([email protected]) and 
* Glenn Fowler ([email protected]). Landon Curt Noll ([email protected]) 
* later improved on their algorithm. 
* 
* The magic is in the interesting relationship between the special prime 
* 16777619 (2^24 + 403) and 2^32 and 2^8. 
* 
* This hash produces the fewest collisions of any function that we've seen so 
* far, and works well on both numbers and strings. 
*/
uint calc_hashnr(const byte *key, uint len)
{
const byte *end=key+len;
uint hash; 

for (hash = 0; key < end; key++)
{
hash *= 16777619;
hash ^= (uint) *(uchar*) key;
} 

return (hash);
} 

uint calc_hashnr_caseup(const byte *key, uint len)
{
const byte *end=key+len;
uint hash; 

for (hash = 0; key < end; key++)
{
hash *= 16777619;
hash ^= (uint) (uchar) toupper(*key);
} 

return (hash);
}
#endif

Mysql中對字串Hash函式還區分了大小寫

●另一個經典字串Hash函式

unsigned int hash(char *str)
{
register unsigned int h;
register unsigned char *p; 

for(h=0, p = (unsigned char *)str; *p ; p++)
h = 31 * h + *p; 

return h;
}