How to store a 64 bit integer in two 32 bit integers and convert back again

pack:

u32 x, y;
u64 v = ((u64)x) << 32 | y;

unpack:

x = (u32)((v & 0xFFFFFFFF00000000LL) >> 32);
y = (u32)(v & 0xFFFFFFFFLL);