title: Hashing of pointer values
body: <p>Sometimes you need to take a hash function of a pointer; not the object the pointer points to, but the pointer itself.  Lots of the time, folks just punt and use the pointer value as an integer, chop off some high bits to make it fit, maybe shift out known-zero bits at the bottom.  Thing is, pointer values aren't necessarily well-distributed in the code space; in fact, if your allocator is doing its job, there's an excellent chance they're all clustered close together.</p>
  
  <p>So, my question is, has anyone developed hash functions that are good for this?  Take a 32- or 64-bit value that's maybe got 12 bits of entropy in it <em>somewhere</em> and spread it evenly across a 32-bit number space.</p>