128 bit Integer hash function

Question

Looking for a string to integer hash function with values in the range of mysql bigint unsigned datatype (0 <= n <= 18446744073709551615). Converting md5/sha1 to integer with the base of 16 does not fit this requirement.

Answer 1

Java uses a rolling hash that should work for you

From java.lang.String :

public int hashCode() {
    int h = hash;
    if (h == 0 && count > 0) {
        int off = offset;
        char val[] = value;
        int len = count;

        for (int i = 0; i < len; i++) {
            h = 31*h + val[off++];
        }
        hash = h;
    }
    return h;
}

The idea is to calculate the hash as :

s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]

To deal with overflow, you can add a step where the hash is checked against 18446744073709551615 and if it is larger take the mod of the hash and 18446744073709551615.