https://github.com/Microsoft/mssql-jdbc: Microsoft JDBC Driver for SQL Server. (Microsoft Corporation) 
package mssql.googlecode.cityhash;


Copyright (C) 2012 tamtam180
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a
copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations
under the License.

Author:tamtam180 - kirscheless at gmail.com
See Also:
/**
 * Copyright (C) 2012 tamtam180
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a
 * copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations
 * under the License.
 *
 * @author tamtam180 - kirscheless at gmail.com
 * @see <a href=
 *      "http://google-opensource.blogspot.jp/2011/04/introducing-cityhash.html">http://google-opensource.blogspot.jp/2011/04/introducing-cityhash.html</a>
 * @see <a href="http://code.google.com/p/cityhash/">http://code.google.com/p/cityhash/</a>
 */
public final class CityHash {

    private static final long k0 = 0xc3a5c85c97cb3127L;
    private static final long k1 = 0xb492b66fbe98f273L;
    private static final long k2 = 0x9ae16a3b2f90404fL;
    private static final long k3 = 0xc949d7c7509e6557L;

    private static long toLongLE(byte[] b,
            int i) {
        return (((long) b[i + 7] << 56) + ((long) (b[i + 6] & 255) << 48) + ((long) (b[i + 5] & 255) << 40) + ((long) (b[i + 4] & 255) << 32)
                + ((long) (b[i + 3] & 255) << 24) + ((b[i + 2] & 255) << 16) + ((b[i + 1] & 255) << 8) + ((b[i + 0] & 255) << 0));
    }

    private static int toIntLE(byte[] b,
            int i) {
        return (((b[i + 3] & 255) << 24) + ((b[i + 2] & 255) << 16) + ((b[i + 1] & 255) << 8) + ((b[i + 0] & 255) << 0));
    }

    private static long fetch64(byte[] s,
            int pos) {
        return toLongLE(s, pos);
    }

    private static int fetch32(byte[] s,
            int pos) {
        return toIntLE(s, pos);
    }

    private static long rotate(long val,
            int shift) {
        return shift == 0 ? val : (val >>> shift) | (val << (64 - shift));
    }

    private static long rotateByAtLeast1(long val,
            int shift) {
        return (val >>> shift) | (val << (64 - shift));
    }

    private static long shiftMix(long val) {
        return val ^ (val >>> 47);
    }

    private static final long kMul = 0x9ddfea08eb382d69L;

    private static long hash128to64(long u,
            long v) {
        long a = (u ^ v) * kMul;
        a ^= (a >>> 47);
        long b = (v ^ a) * kMul;
        b ^= (b >>> 47);
        b *= kMul;
        return b;
    }

    private static long hashLen16(long u,
            long v) {
        return hash128to64(u, v);
    }

    private static long hashLen0to16(byte[] s,
            int pos,
            int len) {
        if (len > 8) {
            long a = fetch64(s, pos + 0);
            long b = fetch64(s, pos + len - 8);
            return hashLen16(a, rotateByAtLeast1(b + len, len)) ^ b;
        }
        if (len >= 4) {
            long a = 0xffffffffL & fetch32(s, pos + 0);
            return hashLen16((a << 3) + len, 0xffffffffL & fetch32(s, pos + len - 4));
        }
        if (len > 0) {
            int a = s[pos + 0] & 0xFF;
            int b = s[pos + (len >>> 1)] & 0xFF;
            int c = s[pos + len - 1] & 0xFF;
            int y = a + (b << 8);
            int z = len + (c << 2);
            return shiftMix(y * k2 ^ z * k3) * k2;
        }
        return k2;
    }

    private static long hashLen17to32(byte[] s,
            int pos,
            int len) {
        long a = fetch64(s, pos + 0) * k1;
        long b = fetch64(s, pos + 8);
        long c = fetch64(s, pos + len - 8) * k2;
        long d = fetch64(s, pos + len - 16) * k0;
        return hashLen16(rotate(a - b, 43) + rotate(c, 30) + d, a + rotate(b ^ k3, 20) - c + len);
    }

    private static long[] weakHashLen32WithSeeds(long w,
            long x,
            long y,
            long z,
            long a,
            long b) {

        a += w;
        b = rotate(b + a + z, 21);
        long c = a;
        a += x;
        a += y;
        b += rotate(a, 44);
        return new long[] {a + z, b + c};
    }

    private static long[] weakHashLen32WithSeeds(byte[] s,
            int pos,
            long a,
            long b) {
        return weakHashLen32WithSeeds(fetch64(s, pos + 0), fetch64(s, pos + 8), fetch64(s, pos + 16), fetch64(s, pos + 24), a, b);
    }

    private static long hashLen33to64(byte[] s,
            int pos,
            int len) {

        long z = fetch64(s, pos + 24);
        long a = fetch64(s, pos + 0) + (fetch64(s, pos + len - 16) + len) * k0;
        long b = rotate(a + z, 52);
        long c = rotate(a, 37);

        a += fetch64(s, pos + 8);
        c += rotate(a, 7);
        a += fetch64(s, pos + 16);

        long vf = a + z;
        long vs = b + rotate(a, 31) + c;

        a = fetch64(s, pos + 16) + fetch64(s, pos + len - 32);
        z = fetch64(s, pos + len - 8);
        b = rotate(a + z, 52);
        c = rotate(a, 37);
        a += fetch64(s, pos + len - 24);
        c += rotate(a, 7);
        a += fetch64(s, pos + len - 16);

        long wf = a + z;
        long ws = b + rotate(a, 31) + c;
        long r = shiftMix((vf + ws) * k2 + (wf + vs) * k0);

        return shiftMix(r * k0 + vs) * k2;

    }

    static long cityHash64(byte[] s,
            int pos,
            int len) {

        if (len <= 32) {
            if (len <= 16) {
                return hashLen0to16(s, pos, len);
            }
            else {
                return hashLen17to32(s, pos, len);
            }
        }
        else if (len <= 64) {
            return hashLen33to64(s, pos, len);
        }

        long x = fetch64(s, pos + len - 40);
        long y = fetch64(s, pos + len - 16) + fetch64(s, pos + len - 56);
        long z = hashLen16(fetch64(s, pos + len - 48) + len, fetch64(s, pos + len - 24));

        long[] v = weakHashLen32WithSeeds(s, pos + len - 64, len, z);
        long[] w = weakHashLen32WithSeeds(s, pos + len - 32, y + k1, x);
        x = x * k1 + fetch64(s, pos + 0);

        len = (len - 1) & (~63);
        do {
            x = rotate(x + y + v[0] + fetch64(s, pos + 8), 37) * k1;
            y = rotate(y + v[1] + fetch64(s, pos + 48), 42) * k1;
            x ^= w[1];
            y += v[0] + fetch64(s, pos + 40);
            z = rotate(z + w[0], 33) * k1;
            v = weakHashLen32WithSeeds(s, pos + 0, v[1] * k1, x + w[0]);
            w = weakHashLen32WithSeeds(s, pos + 32, z + w[1], y + fetch64(s, pos + 16));
            {
                long swap = z;
                z = x;
                x = swap;
            }
            pos += 64;
            len -= 64;
        }
        while (len != 0);

        return hashLen16(hashLen16(v[0], w[0]) + shiftMix(y) * k1 + z, hashLen16(v[1], w[1]) + x);

    }

    static long cityHash64WithSeed(byte[] s,
            int pos,
            int len,
            long seed) {
        return cityHash64WithSeeds(s, pos, len, k2, seed);
    }

    static long cityHash64WithSeeds(byte[] s,
            int pos,
            int len,
            long seed0,
            long seed1) {
        return hashLen16(cityHash64(s, pos, len) - seed0, seed1);
    }

    static long[] cityMurmur(byte[] s,
            int pos,
            int len,
            long seed0,
            long seed1) {

        long a = seed0;
        long b = seed1;
        long c = 0;
        long d = 0;

        int l = len - 16;
        if (l <= 0) {
            a = shiftMix(a * k1) * k1;
            c = b * k1 + hashLen0to16(s, pos, len);
            d = shiftMix(a + (len >= 8 ? fetch64(s, pos + 0) : c));
        }
        else {

            c = hashLen16(fetch64(s, pos + len - 8) + k1, a);
            d = hashLen16(b + len, c + fetch64(s, pos + len - 16));
            a += d;

            do {
                a ^= shiftMix(fetch64(s, pos + 0) * k1) * k1;
                a *= k1;
                b ^= a;
                c ^= shiftMix(fetch64(s, pos + 8) * k1) * k1;
                c *= k1;
                d ^= c;
                pos += 16;
                l -= 16;
            }
            while (l > 0);
        }

        a = hashLen16(a, c);
        b = hashLen16(d, b);

        return new long[] {a ^ b, hashLen16(b, a)};

    }

    static long[] cityHash128WithSeed(byte[] s,
            int pos,
            int len,
            long seed0,
            long seed1) {

        if (len < 128) {
            return cityMurmur(s, pos, len, seed0, seed1);
        }

        long[] v = new long[2], w = new long[2];
        long x = seed0;
        long y = seed1;
        long z = k1 * len;

        v[0] = rotate(y ^ k1, 49) * k1 + fetch64(s, pos);
        v[1] = rotate(v[0], 42) * k1 + fetch64(s, pos + 8);
        w[0] = rotate(y + z, 35) * k1 + x;
        w[1] = rotate(x + fetch64(s, pos + 88), 53) * k1;

        do {
            x = rotate(x + y + v[0] + fetch64(s, pos + 8), 37) * k1;
            y = rotate(y + v[1] + fetch64(s, pos + 48), 42) * k1;

            x ^= w[1];
            y += v[0] + fetch64(s, pos + 40);
            z = rotate(z + w[0], 33) * k1;
            v = weakHashLen32WithSeeds(s, pos + 0, v[1] * k1, x + w[0]);
            w = weakHashLen32WithSeeds(s, pos + 32, z + w[1], y + fetch64(s, pos + 16));
            {
                long swap = z;
                z = x;
                x = swap;
            }
            pos += 64;
            x = rotate(x + y + v[0] + fetch64(s, pos + 8), 37) * k1;
            y = rotate(y + v[1] + fetch64(s, pos + 48), 42) * k1;
            x ^= w[1];
            y += v[0] + fetch64(s, pos + 40);
            z = rotate(z + w[0], 33) * k1;
            v = weakHashLen32WithSeeds(s, pos, v[1] * k1, x + w[0]);
            w = weakHashLen32WithSeeds(s, pos + 32, z + w[1], y + fetch64(s, pos + 16));
            {
                long swap = z;
                z = x;
                x = swap;
            }
            pos += 64;
            len -= 128;
        }
        while (len >= 128);

        x += rotate(v[0] + z, 49) * k0;
        z += rotate(w[0], 37) * k0;

        for (int tail_done = 0; tail_done < len;) {
            tail_done += 32;
            y = rotate(x + y, 42) * k0 + v[1];
            w[0] += fetch64(s, pos + len - tail_done + 16);
            x = x * k0 + w[0];
            z += w[1] + fetch64(s, pos + len - tail_done);
            w[1] += v[0];
            v = weakHashLen32WithSeeds(s, pos + len - tail_done, v[0] + z, v[1]);
        }

        x = hashLen16(x, v[0]);
        y = hashLen16(y + z, w[0]);

        return new long[] {hashLen16(x + v[1], w[1]) + y, hashLen16(x + w[1], y + v[1])};

    }

    public static long[] cityHash128(byte[] s,
            int pos,
            int len) {

        if (len >= 16) {
            return cityHash128WithSeed(s, pos + 16, len - 16, fetch64(s, pos + 0) ^ k3, fetch64(s, pos + 8));
        }
        else if (len >= 8) {
            return cityHash128WithSeed(new byte[0], 0, 0, fetch64(s, pos + 0) ^ (len * k0), fetch64(s, pos + len - 8) ^ k1);
        }
        else {
            return cityHash128WithSeed(s, pos, len, k0, k1);
        }
    }
}