Majors hash function implementation in C

hash.cpp

#include "hash.hh"

HashFunc::HashFunc ()
{
}

HashFunc::~HashFunc ()
{
}

uint
HashFunc::ELFHash(const char* str, uint len)
{
  return this->ELFHash(str, len, 0);
}

uint
HashFunc::ELFHash(const char* str, uint len, uint hash)
{
   uint x    = 0;
   uint 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;
}

uint
HashFunc::RSHash(const char* str, uint len)
{
  return this->RSHash(str, len, 0);
}

uint
HashFunc::RSHash(const char* str, uint len, uint hash)
{
   uint b    = 378551;
   uint a    = 63689;
   uint i    = 0;

   for(i = 0; i < len; str++, i++)
   {
      hash = hash * a + (*str);
      a    = a * b;
   }

   return hash;
}
/* End Of RS Hash Function */

uint
HashFunc::JSHash(const char* str, uint len)
{
  return this->JSHash(str, len, 1315423911);
}

uint
HashFunc::JSHash(const char* str, uint len, uint hash)
{
   uint i    = 0;

   for(i = 0; i < len; str++, i++)
   {
      hash ^= ((hash << 5) + (*str) + (hash >> 2));
   }

   return hash;
}
/* End Of JS Hash Function */

uint
HashFunc::PJWHash(const char* str, uint len)
{
  return this->PJWHash(str, len, 0);
}

uint
HashFunc::PJWHash(const char* str, uint len, uint hash)
{
   const uint BitsInUnsignedInt = (uint)(sizeof(uint) * 8);
   const uint ThreeQuarters     = (uint)((BitsInUnsignedInt  * 3) / 4);
   const uint OneEighth         = (uint)(BitsInUnsignedInt / 8);
   const uint HighBits          = (uint)(0xFFFFFFFF) << (BitsInUnsignedInt - OneEighth);
   uint test              = 0;
   uint 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 */


uint
HashFunc::BKDRHash(const char* str, uint len)
{
  return this->BKDRHash(str, len, 0);
}
uint
HashFunc::BKDRHash(const char* str, uint len, uint hash)
{
   uint seed = 131; /* 31 131 1313 13131 131313 etc.. */
   uint i    = 0;

   for(i = 0; i < len; str++, i++)
   {
      hash = (hash * seed) + (*str);
   }

   return hash;
}
/* End Of BKDR Hash Function */


uint
HashFunc::SDBMHash(const char* str, uint len)
{
  return this->SDBMHash(str, len, 0);
}

uint
HashFunc::SDBMHash(const char* str, uint len, uint hash)
{
   uint i    = 0;

   for(i = 0; i < len; str++, i++)
   {
      hash = (*str) + (hash << 6) + (hash << 16) - hash;
   }

   return hash;
}
/* End Of SDBM Hash Function */


uint
HashFunc::DJBHash(const char* str, uint len)
{
  return this->DJBHash(str, len, 5381);
}

uint
HashFunc::DJBHash(const char* str, uint len, uint hash)
{
   uint i    = 0;

   for(i = 0; i < len; str++, i++)
   {
      hash = ((hash << 5) + hash) + (*str);
   }

   return hash;
}
/* End Of DJB Hash Function */
uint
HashFunc::DEKHash(const char* str, uint len)
{
  return this->DEKHash(str, len, len);
}

uint
HashFunc::DEKHash(const char* str, uint len, uint hash)
{
   uint i    = 0;

   for(i = 0; i < len; str++, i++)
   {
      hash = ((hash << 5) ^ (hash >> 27)) ^ (*str);
   }
   return hash;
}
/* End Of DEK Hash Function */


uint
HashFunc::BPHash(const char* str, uint len)
{
  return this->BPHash(str, len, 0);
}

uint
HashFunc::BPHash(const char* str, uint len, uint hash)
{
   uint i    = 0;
   for(i = 0; i < len; str++, i++)
   {
      hash = hash << 7 ^ (*str);
   }

   return hash;
}
/* End Of BP Hash Function */


uint
HashFunc::FNVHash(const char* str, uint len)
{
  return this->FNVHash(str, len, 0);
}

uint
HashFunc::FNVHash(const char* str, uint len, uint hash)
{
   const uint fnv_prime = 0x811C9DC5;
   uint i         = 0;

   for(i = 0; i < len; str++, i++)
   {
      hash *= fnv_prime;
      hash ^= (*str);
   }

   return hash;
}
/* End Of FNV Hash Function */

uint
HashFunc::APHash(const char* str, uint len)
{
  return this->APHash(str, len, 0xAAAAAAAA);
}

uint
HashFunc::APHash(const char* str, uint len, uint hash)
{
   uint 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;
}

hash.hh

#ifndef HASH_HH_
# define HASH_HH_

# include <cstring>
# include <iostream>
# include <istream>
# include <fstream>

typedef unsigned int uint;

class HashFunc
{
public:

  HashFunc ();
  ~HashFunc ();

  /**
   * Private string hashing methods
   */
  uint FNVHash (const char* str, uint len); // 1 Best one
  uint SDBMHash (const char* str, uint len); // 2 Second Best one
  uint APHash (const char* str, uint len); // 3 Third Best one
  uint RSHash (const char* str, uint len); // 4
  uint BKDRHash (const char* str, uint len); // 4
  uint DJBHash (const char* str, uint len); // 5
  uint JSHash (const char* str, uint len); // 6
  uint DEKHash (const char* str, uint len); // 6
  uint ELFHash (const char* str, uint len); // 7
  uint PJWHash (const char* str, uint len); // 7
  uint BPHash (const char* str, uint len); // 8

  uint FNVHash (const char* str, uint len, uint hash);
  uint SDBMHash (const char* str, uint len, uint hash);
  uint APHash (const char* str, uint len, uint hash);
  uint RSHash (const char* str, uint len, uint hash);
  uint BKDRHash (const char* str, uint len, uint hash);
  uint DJBHash (const char* str, uint len, uint hash);
  uint JSHash (const char* str, uint len, uint hash);
  uint DEKHash (const char* str, uint len, uint hash);
  uint ELFHash (const char* str, uint len, uint hash);
  uint PJWHash (const char* str, uint len, uint hash);
  uint BPHash (const char* str, uint len, uint hash);
};

#endif /* !HASH_HH_ */