static UInt128 CityHash128WithSeed(byte[] s, int len, UInt128 seed, int off)
{
if (len < 128)
{
return(CityMurmur(s, len, seed, off));
}
// We expect len >= 128 to be the common case. Keep 56 bytes of state:
// v, w, x, y, and z.
UInt128 v = new UInt128(), w = new UInt128();
ulong x = seed.Low;
ulong y = seed.High;
ulong z = (ulong)len * k1;
v.Low = Rotate(y ^ k1, 49) * k1 + Fetch64(s, off);
v.High = Rotate(v.Low, 42) * k1 + Fetch64(s, off + 8);
w.Low = Rotate(y + z, 35) * k1 + x;
w.High = Rotate(x + Fetch64(s, off + 88), 53) * k1;
// This is the same inner loop as CityHash64(), manually unrolled.
ulong swp;
do
{
x = Rotate(x + y + v.Low + Fetch64(s, off + 16), 37) * k1;
y = Rotate(y + v.High + Fetch64(s, off + 48), 42) * k1;
x ^= w.High;
y ^= v.Low;
z = Rotate(z ^ w.Low, 33);
v = WeakHashLen32WithSeeds(s, v.High * k1, x + w.Low, off);
w = WeakHashLen32WithSeeds(s, z + w.High, y, off + 32);
swp = z;
z = x;
x = swp;
off += 64;
x = Rotate(x + y + v.Low + Fetch64(s, off + 16), 37) * k1;
y = Rotate(y + v.High + Fetch64(s, off + 48), 42) * k1;
x ^= w.High;
y ^= v.Low;
z = Rotate(z ^ w.Low, 33);
v = WeakHashLen32WithSeeds(s, v.High * k1, x + w.Low, off);
w = WeakHashLen32WithSeeds(s, z + w.High, y, off + 32);
swp = z;
z = x;
x = swp;
off += 64;
len -= 128;
} while ((len >= 128));
y += Rotate(w.Low, 37) * k0 + z;
x += Rotate(v.Low + z, 49) * k0;
// If 0 < len < 128, hash up to 4 chunks of 32 bytes each from the end of s.
for (int tail_done = 0; tail_done < len;)
{
tail_done += 32;
y = Rotate(y - x, 42) * k0 + v.High;
w.Low += Fetch64(s, off + len - tail_done + 16);
x = Rotate(x, 49) * k0 + w.Low;
w.Low += v.Low;
v = WeakHashLen32WithSeeds(s, v.Low, v.High, off + len - tail_done);
}
// At this point our 48 bytes of state should contain more than
// enough information for a strong 128-bit hash. We use two
// different 48-byte-to-8-byte hashes to get a 16-byte final result.
x = HashLen16(x, v.Low);
y = HashLen16(y, w.Low);
return(new UInt128(HashLen16(x + v.High, w.High) + y,
HashLen16(x + w.High, y + v.High)));
}
protected abstract byte[] Decompress(Stream compressed, out UInt128 compressedHash);
