Function to combine two int32 into 1 int64.

pack.cpp

static int64_t Pack(int32_t inX, int32_t inY)
{
    int64_t x = static_cast<int64_t>(inX) << 32;
    int64_t y = static_cast<int64_t>(inY);

    // twos complement, therefore 32 msbs must be cleared.
    if (inY < 0)
    {
        y = y ^ 0xFFFFFFFF00000000;
    }
    
    return x | y;
}