# (MARK)各种字符串hash算法

[ ]

The content is recoverd from Wordpress Blog, for more details please check HERE

##### December 17, 2014

VOID001 Comments 0 Comment

``````// RS Hash Function
unsigned int RSHash(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 );
}

// JS Hash Function
unsigned int JSHash(char* str)
{
unsigned int hash = 1315423911 ;
while (*str)
{
hash ^= ((hash << 5 ) + (*str ++ ) + (hash >> 2 ));
}
return (hash & 0x7FFFFFFF );
}

// P. J. Weinberger Hash Function
unsigned int PJWHash(char* str)
{
unsigned int BitsInUnignedInt = (unsigned int )( sizeof (unsigned int)*8 );
unsigned int ThreeQuarters = (unsigned int )((BitsInUnignedInt*3 ) / 4 );
unsigned int OneEighth = (unsigned int )(BitsInUnignedInt / 8 );
unsigned int HighBits = (unsigned int )( 0xFFFFFFFF ) << (BitsInUnignedInt - 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 );
}

// ELF Hash Function
unsigned int ELFHash(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 );
}

// BKDR Hash Function
unsigned int BKDRHash(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 );
}

// SDBM Hash Function
unsigned int SDBMHash(char* str)
{
unsigned int hash = 0 ;
while (*str)
{
hash = (*str ++ ) + (hash << 6 ) + (hash << 16 ) - hash;
}
return (hash & 0x7FFFFFFF );
}

// DJB Hash Function
unsigned int DJBHash(char* str)
{
unsigned int hash = 5381 ;
while (*str)
{
hash += (hash << 5 ) + (*str ++ );
}
return (hash & 0x7FFFFFFF );
}

// AP Hash Function
unsigned int APHash(char* str)
{
unsigned int hash = 0 ;
int i;
for (i = 0 ;*str; i ++ )
{
if ((i & 1 ) The content is recoverd from Wordpress Blog, for more details please check [HERE](recover-my-blog) 0 )    {
hash ^= ((hash << 7 ) ^ (*str ++ ) ^ (hash >> 3 ));
}    else {
hash ^= ( ~ ((hash << 11 ) ^ (*str ++ ) ^ (hash >> 5 )));
}
}
return (hash & 0x7FFFFFFF );
}
``````