static long hash()

in datasketches-memory-java8/src/main/java/org/apache/datasketches/memory/internal/XxHash64.java [79:172]
78 lines of code
6 McCabe index (conditional complexity)

  static long hash(final Object unsafeObj, long cumOffsetBytes, final long lengthBytes,
      final long seed) {
    long hash;
    long remaining = lengthBytes;

    if (remaining >= 32) {
      long v1 = seed + P1 + P2;
      long v2 = seed + P2;
      long v3 = seed;
      long v4 = seed - P1;

      do {
        v1 += unsafe.getLong(unsafeObj, cumOffsetBytes) * P2;
        v1 = Long.rotateLeft(v1, 31);
        v1 *= P1;

        v2 += unsafe.getLong(unsafeObj, cumOffsetBytes + 8L) * P2;
        v2 = Long.rotateLeft(v2, 31);
        v2 *= P1;

        v3 += unsafe.getLong(unsafeObj, cumOffsetBytes + 16L) * P2;
        v3 = Long.rotateLeft(v3, 31);
        v3 *= P1;

        v4 += unsafe.getLong(unsafeObj, cumOffsetBytes + 24L) * P2;
        v4 = Long.rotateLeft(v4, 31);
        v4 *= P1;

        cumOffsetBytes += 32;
        remaining -= 32;
      } while (remaining >= 32);

      hash = Long.rotateLeft(v1, 1)
          + Long.rotateLeft(v2, 7)
          + Long.rotateLeft(v3, 12)
          + Long.rotateLeft(v4, 18);

      v1 *= P2;
      v1 = Long.rotateLeft(v1, 31);
      v1 *= P1;
      hash ^= v1;
      hash = (hash * P1) + P4;

      v2 *= P2;
      v2 = Long.rotateLeft(v2, 31);
      v2 *= P1;
      hash ^= v2;
      hash = (hash * P1) + P4;

      v3 *= P2;
      v3 = Long.rotateLeft(v3, 31);
      v3 *= P1;
      hash ^= v3;
      hash = (hash * P1) + P4;

      v4 *= P2;
      v4 = Long.rotateLeft(v4, 31);
      v4 *= P1;
      hash ^= v4;
      hash = (hash * P1) + P4;
    } //end remaining >= 32
    else {
      hash = seed + P5;
    }

    hash += lengthBytes;

    while (remaining >= 8) {
      long k1 = unsafe.getLong(unsafeObj, cumOffsetBytes);
      k1 *= P2;
      k1 = Long.rotateLeft(k1, 31);
      k1 *= P1;
      hash ^= k1;
      hash = (Long.rotateLeft(hash, 27) * P1) + P4;
      cumOffsetBytes += 8;
      remaining -= 8;
    }

    if (remaining >= 4) { //treat as unsigned ints
      hash ^= (unsafe.getInt(unsafeObj, cumOffsetBytes) & 0XFFFF_FFFFL) * P1;
      hash = (Long.rotateLeft(hash, 23) * P2) + P3;
      cumOffsetBytes += 4;
      remaining -= 4;
    }

    while (remaining != 0) { //treat as unsigned bytes
      hash ^= (unsafe.getByte(unsafeObj, cumOffsetBytes) & 0XFFL) * P5;
      hash = Long.rotateLeft(hash, 11) * P1;
      --remaining;
      ++cumOffsetBytes;
    }

    return finalize(hash);
  }