字符串各种hash函数

深碍√TFBOYSˉ_ 2021-10-23 21:40 289阅读 0赞

附：各种哈希函数的C语言程序代码
    unsigned int SDBMHash(char *str)
    {
        unsigned int hash = 0;
     
        while (*str)
        {
            // equivalent to: hash = 65599*hash + (*str++);
            hash = (*str++) + (hash << 6) + (hash << 16) - hash;
        }
     
        return (hash & 0x7FFFFFFF);
    }
     
    // 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);
    }
     
    // 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);
    }