若干经典的字符串哈希函数 C/C++编程

// 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 ) << (BitsInU
nignedInt - 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 ) == 0 )
{
hash ^= ((hash << 7 ) ^ ( * str ++ ) ^ (hash >> 3 ));
}
else
{
hash ^= ( ~ ((hash << 11 ) ^ ( * str ++ ) ^ (hash >> 5 )));
}
}

return (hash & 0x7FFFFFFF );
}
比较经典的字符串hash就这些了吧,"ELF Hash Function" <-这个比较常用..