常用Hash算法(C语言的简单实现)

如下所示：

#include "GeneralHashFunctions.h" 
 
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 */ 

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