目录

• 根据字符串生成Hash值 唯一ID值
  • 一丶Hash函数
    • 1.APHash
    • 2.RsHash
    • 3.jsHash
    • 4.PJW Hash
    • 5.ELF Hash
    • 6.BKDR Hash
    • 7.SDMB Hash
    • 8.DJB Hash
    • 9.DEKHash
  • 二丶代码下载

根据字符串生成Hash值 唯一ID值

参考网址: http://www.partow.net/programming/hashfunctions/

一丶Hash函数

1.APHash

APHash

uint32_t hash(const char* message, size_t message_length)
{
   uint32_t internal_state = 0xA5A5A5A5; // IV: A magic number
   uint32_t message_block = 0;

   // Loop over the message 32-bits at-a-time
   while (message_length >= 4)
   {
      memcpy(message_block, message, sizeof(uint32_t));

      internal_state = mix(message_block, internal_state);

      message_length -= sizeof(uint32_t);
      message        += sizeof(uint32_t);
   }

   // Are there any remaining bytes?
   if (message_length)
   {
      memcpy(message_block, message, message_length);
      internal_state = mix(message_block, internal_state);
   }

   return internal_state;
}

另一种
// 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);
}

2.RsHash

unsigned int RSHash(const char* str, unsigned int length)
{
   unsigned int b    = 378551;
   unsigned int a    = 63689;
   unsigned int hash = 0;
   unsigned int i    = 0;

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

   return hash;
}

3.jsHash

unsigned int JSHash(const char* str, unsigned int length)
{
   unsigned int hash = 1315423911;
   unsigned int i    = 0;

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

   return hash;
}

4.PJW Hash

nsigned int PJWHash(const char* str, unsigned int length)
{
   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 < length; ++str, ++i)
   {
      hash = (hash << OneEighth) + (*str);

      if ((test = hash & HighBits) != 0)
      {
         hash = (( hash ^ (test >> ThreeQuarters)) & (~HighBits));
      }
   }

   return hash;
}

5.ELF Hash

unsigned int ELFHash(const char* str, unsigned int length)
{
   unsigned int hash = 0;
   unsigned int x    = 0;
   unsigned int i    = 0;

   for (i = 0; i < length; ++str, ++i)
   {
      hash = (hash << 4) + (*str);

      if ((x = hash & 0xF0000000L) != 0)
      {
         hash ^= (x >> 24);
      }

      hash &= ~x;
   }

   return hash;
}

6.BKDR Hash

unsigned int BKDRHash(const char* str, unsigned int length)
{
   unsigned int seed = 131; /* 31 131 1313 13131 131313 etc.. */
   unsigned int hash = 0;
   unsigned int i    = 0;

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

   return hash;
}

7.SDMB Hash

unsigned int SDBMHash(const char* str, unsigned int length)
{
   unsigned int hash = 0;
   unsigned int i    = 0;

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

   return hash;
}

8.DJB Hash

unsigned int DJBHash(const char* str, unsigned int length)
{
   unsigned int hash = 5381;
   unsigned int i    = 0;

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

   return hash;
}

9.DEKHash

unsigned int DEKHash(const char* str, unsigned int length)
{
   unsigned int hash = len;
   unsigned int i    = 0;

   for (i = 0; i < length; ++str, ++i)
   {
      hash = ((hash << 5) ^ (hash >> 27)) ^ (*str);
   }

   return hash;
}

二丶代码下载

链接：https://pan.baidu.com/s/1gXE4O7y2dJmCoGO6AuandQ 提取码：1111