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 */ 

以上就是小编为大家带来的常用Hash算法(C语言的简单实现)的全部内容了，希望对大家有所帮助，多多支持我们~