转一下常见的常用的哈希函数

转载自 http://blog.csdn.net/alongela/article/details/8247713

const int MOD = 10007;

unsigned int RSHash(const char* str)
{
unsigned int b = 378551;
unsigned int a = 63689;
unsigned int hash = 0;
while (*str)
{
hash = hash * a + *str++;
a *= b;
}
return (hash & 0x7fffffff) % MOD;
}

unsigned int JSHash(const char* str)
{
unsigned int hash = 1315423911;
while (*str)
{
hash ^= ((hash << 5) + *str++ + (hash >> 2));
}
return (hash & 0x7fffffff) % MOD;
}

unsigned int PJWHash(const char* str)
{
unsigned int BitsInUnsignedInt = (unsigned int)(sizeof(unsigned int) * 8);
unsigned int ThreeQuarters = (unsigned int)((BitsInUnsignedInt * 3) / 4);
unsigned int OneEighth = (unsigned int)(BitsInUnsignedInt / 8);
unsigned int HighBits = (unsigned int)(0xffffffff) << (BitsInUnsignedInt - OneEighth);
unsigned int hash = 0;
unsigned int test = 0;
while (*str)
{
hash = (hash << OneEighth) + *str++;
if((test = hash & HighBits) != 0)
{
hash = (( hash ^ (test >> ThreeQuarters)) & (~HighBits));
}
}
return (hash & 0x7fffffff) % MOD;
}

unsigned int ELFHash(const char* str)
{
unsigned int hash = 0;
unsigned int x = 0;
while (*str)
{
hash = (hash << 4) + *str++;
if((x = hash & 0xF0000000L) != 0)
{
hash ^= (x >> 24);
}
hash &= ~x;
}
return (hash & 0x7fffffff) % MOD;
}

unsigned int BKDRHash(const char* str)
{
unsigned int seed = 131; // 31 131 1313 13131 131313 etc..
unsigned int hash = 0;
while (*str)
{
hash = (hash * seed) + *str++;
}
return (hash & 0x7fffffff) % MOD;
}

unsigned int SDBMHash(const char* str)
{
unsigned int hash = 0;
while (*str)
{
hash = *str++ + (hash << 6) + (hash << 16) - hash;
}
return (hash & 0x7fffffff) % MOD;
}

unsigned int DJBHash(const char* str)
{
unsigned int hash = 5381;
while (*str)
{
hash = ((hash << 5) + hash) + *str++;
}
return (hash & 0x7fffffff) % MOD;
}

unsigned int DEKHash(const char* str)
{
unsigned int hash = static_cast<unsigned int>(strlen(str));
while (*str)
{
hash = ((hash << 5) ^ (hash >> 27)) ^ *str++;
}
return (hash & 0x7fffffff) % MOD;
}

unsigned int BPHash(const char* str)
{
unsigned int hash = 0;
while (*str)
{
hash = hash << 7 ^ *str++;
}
return (hash & 0x7fffffff) % MOD;
}

unsigned int FNVHash(const char* str)
{
const unsigned int fnv_prime = 0x811C9DC5;
unsigned int hash = 0;
while (*str)
{
hash *= fnv_prime;
hash ^= *str++;
}
return (hash & 0x7fffffff) % MOD;
}

unsigned int APHash(const char* str)
{
unsigned int hash = 0xAAAAAAAA;
for(int i = 0; str[i] != 0; ++i)
{
hash ^= ((i & 1) == 0) ? ( (hash << 7) ^ str[i] * (hash >> 3)) :
(~((hash << 11) + (str[i] ^ (hash >> 5))));
}
return (hash & 0x7fffffff) % MOD;
}

转载自 http://blog.csdn.net/alongela/article/details/8247713