rbc: use struct unpack_from and pack_into instead of unpack and pack...
rbc: use struct unpack_from and pack_into instead of unpack and pack
These functions were introduced in Python 2.5 and are faster and simpler than
the old ones ... mainly because we can avoid intermediate buffers:
$ python -m timeit -s "_rbcrecfmt='>4sI'" -s 's = "x"*10000' -s 'from struct import unpack' 'unpack(_rbcrecfmt, buffer(s, 16, 8))'
1000000 loops, best of 3: 0.543 usec per loop
$ python -m timeit -s "_rbcrecfmt='>4sI'" -s 's = "x"*10000' -s 'from struct import unpack_from' 'unpack_from(_rbcrecfmt, s, 16)'
1000000 loops, best of 3: 0.323 usec per loop
$ python -m timeit -s "from array import array" -s "_rbcrecfmt='>4sI'" -s "s = array('c')" -s 's.fromstring("x"*10000)' -s 'from struct import pack' -s "rec = array('c')" 'rec.fromstring(pack(_rbcrecfmt, "asdf", 7))'
1000000 loops, best of 3: 0.364 usec per loop
$ python -m timeit -s "from array import array" -s "_rbcrecfmt='>4sI'" -s "s = array('c')" -s 's.fromstring("x"*10000)' -s 'from struct import pack_into' -s "rec = array('c')" -s 'rec.fromstring("x"*100)' 'pack_into(_rbcrecfmt, rec, 0, "asdf", 7)'
1000000 loops, best of 3: 0.229 usec per loop
