Question

I need to create a perfect hash for a list of string identifiers, so before to begin with this implementation (i have never did it before) i want to know if there is any good framework or good tutorial that could be useful?

Thanks!

Answer 1

I use the MurmurHash written by Austin Appleby:

unsigned int Hash (const char* buffer, size_t size, unsigned seed)
{
    const unsigned int m = 0x5bd1e995;
    const int r = 2;
    unsigned int h = seed ^ (unsigned int)size;
    const unsigned char* data = (const unsigned char*)buffer;

    while(size >= 4)
    {
        unsigned int k;

        k = data[0];
        k |= data[1] << 8;
        k |= data[2] << 16;
        k |= data[3] << 24;

        k *= m;
        k ^= k >> r;
        k *= m;

        h *= m;
        h ^= k;

        data += 4;
        size -= 4;
    }

    switch(size)
    {
    case 3:         h ^= data[2] << 16;
    case 2:         h ^= data[1] << 8;
    case 1:         h ^= data[0];
        h *= m;
    }

    h ^= h >> 13;
    h *= m;
    h ^= h >> 15;

    return h;
}

But ultimately your choice of hashing function depends on the trade-off between quality and speed.