Benchmark: timing 100 iterations of openclose, seek...
openclose: 186 wallclock secs (161.45 usr + 19.77 sys = 181.22 CPU) @  0.55/s (n=100)
seek: 17 wallclock secs (16.08 usr +  1.02 sys = 17.10 CPU) @  5.85/s (n=100)