3 bup_python="$(dirname "$0")/bup-python" || exit $?
4 exec "$bup_python" "$0" ${1+"$@"}
8 from __future__ import absolute_import, print_function
9 import sys, struct, math
11 from bup import options, git, _helpers
12 from bup.helpers import log
14 POPULATION_OF_EARTH=6.7e9 # as of September, 2010
19 predict Guess object offsets and report the maximum deviation
20 ignore-midx Don't use midx files; use only plain pack idx files.
22 o = options.Options(optspec)
23 (opt, flags, extra) = o.parse(sys.argv[1:])
26 o.fatal("no arguments expected")
28 git.check_repo_or_die()
29 git.ignore_midx = opt.ignore_midx
31 mi = git.PackIdxList(git.repo('objects/pack'))
36 for count,i in enumerate(ix):
37 prefix = struct.unpack('!Q', i[:8])[0]
38 expected = prefix * total / (1<<64)
39 diff = count - expected
40 maxdiff = max(maxdiff, abs(diff))
41 print('%d of %d (%.3f%%) ' % (maxdiff, len(ix), maxdiff*100.0/len(ix)))
43 assert(count+1 == len(ix))
52 # default mode: find longest matching prefix
58 #assert(str(i) >= last)
59 pm = _helpers.bitmatch(last, i)
60 longmatch = max(longmatch, pm)
63 log('%d matching prefix bits\n' % longmatch)
64 doublings = math.log(len(mi), 2)
65 bpd = longmatch / doublings
66 log('%.2f bits per doubling\n' % bpd)
67 remain = 160 - longmatch
68 rdoublings = remain / bpd
69 log('%d bits (%.2f doublings) remaining\n' % (remain, rdoublings))
70 larger = 2**rdoublings
71 log('%g times larger is possible\n' % larger)
72 perperson = larger/POPULATION_OF_EARTH
73 log('\nEveryone on earth could have %d data sets like yours, all in one\n'
74 'repository, and we would expect 1 object collision.\n'