参考：https://en.wikipedia.org/wiki/List_of_hash_functions

fnv hash

返回值：一个 int 整数

unsigned int fnv_hash (void* key, int len)
{
    unsigned char* p = key;
    unsigned int h = 2166136261;
    int i;

    for (i = 0; i < len; i++)
        h = (h*16777619) ^ p[i];

    return h;
}

Jenkins hash function

uint32_t jenkins_one_at_a_time_hash(char *key, size_t len)
{
    uint32_t hash, i;
    for(hash = i = 0; i < len; ++i)
    {
        hash += key[i];
        hash += (hash << 10);
        hash ^= (hash >> 6);
    }
    hash += (hash << 3);
    hash ^= (hash >> 11);
    hash += (hash << 15);
    return hash;
}

djb2

http://www.cse.yorku.ca/~oz/hash.html

unsigned long hash(unsigned char *str)
{
    unsigned long hash = 5381;
    int c;

    while (c = *str++)
        hash = ((hash << 5) + hash) + c; /* hash * 33 + c */

    return hash;
}

sdbm

unsigned long sdbm(unsigned char *str)
{
    unsigned long hash = 0;
    int c;

    while (c = *str++)
        hash = c + (hash << 6) + (hash << 16) - hash;

    return hash;
}

lose lose

unsigned long hash(unsigned char *str)
{
    unsigned int hash = 0;
    int c;

    while (c = *str++)
        hash += c;

    return hash;
}