# Common string Hash functions

Source: Internet
Author: User

A few commonly used string hash functions are as follows:

Sdbmhash function
`unsigned int sdbmhash (char *str) {    unsigned int hash = 0;     while (*STR)    {        //equivalent To:hash = 65599*hash + (*str++);        hash = (*str++) + (hash << 6) + (hash << +)-hash;    }     `
Rshash function

`RS Hash functionunsigned 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);}`

Jshash function
`JS Hash functionunsigned int Jshash (char *str) {    unsigned int hash = 1315423911;     while (*STR)    {        hash ^= (Hash << 5) + (*str++) + (hash >> 2));    }     Return (hash & 0x7FFFFFFF);}`

Pjwhash function
```P. J. Weinberger Hash functionunsigned int Pjwhash (char *str) {    unsigned int bitsinunignedint = (unsigned int) (Sizeo f (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);}
```
Elfhash function
`ELF Hash functionunsigned 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 >>);            Hash &= ~x;        }    }     Return (hash & 0x7FFFFFFF);}`
Bkdrhash function (recommended)
`BKDR Hash functionunsigned int Bkdrhash (char *str) {    unsigned int seed = 131;//131 1313 13131 131313 etc..    unsigned int hash = 0;     while (*STR)    {        hash = hash * seed + (*str++);    }     `

Djbhash function
`DJB Hash functionunsigned int Djbhash (char *str) {    unsigned int hash = 5381;     while (*STR)    {        hash + = (hash << 5) + (*str++);    }     Return (hash & 0x7FFFFFFF);}`

Aphash function
`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 << one) ^ (*str++) ^ (hash >> 5));}    }     Return (hash & 0x7FFFFFFF);}`

Common string Hash functions

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