常用的字符串hash算法zz

// 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 Functionunsigned 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 Functionunsigned int

SDBMHash(

char

* str)

{

   

unsigned int

hash = 0 ;

    while (*str)

    {

        hash = (*str ++ ) + (hash << 6 ) + (hash << 16 ) – hash;

    }

    return (hash & 0x7FFFFFFF );

}

// DJB Hash Functionunsigned int

DJBHash(

char

* str)

{

   

unsigned int

hash = 5381 ;

    while (*str)

    {

        hash += (hash << 5 ) + (*str ++ );

    }

    return (hash & 0x7FFFFFFF );

}

// AP Hash Functionunsigned 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 );

}