典型Hash算法实现

DJBHash

unsigned int DJBHash(char *str)
{
    unsigned int hash = 5381;
    while(*str) 
    {
        hash = ((hash << 5) + hash) + (*str++); 
    }
    hash &= ~(1 << 31);
    return hash;
}

MurMurHash

uint32_t ngx_murmur_hash2(u_char *data, size_t len)
{
    uint32_t h,k;
    h = 0^len;
    while(len>=4)
    {
        k = data[0];
        k |= data[1] << 8;
        k |= data{2] << 16;
        k |= data[3] << 24;

        k *= 0x5bd1e995;
        k ^= k >> 24;
        k *= 0x5bd1e995;

        data += 4;
        len -= 4;
    }
    switch(len)
    {
        case 3:
            h ^= data[2] << 16;
        case 2:
            h ^= data[1] << 8;
        case 1:
            h ^= data[0];
            h *= 0x5bd1e995;
    }
    h ^= h >> 13;
    h *= 0x5bd1e995;
    h ^= h >> 15;
    
    return h;
}