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#!/usr/bin/env python
import sys, struct
from bup import options, git, _helpers
from bup.helpers import *
optspec = """
bup margin
--
predict Guess object offsets and report the maximum deviation
ignore-midx Don't use midx files; use only plain pack idx files.
"""
o = options.Options('bup margin', optspec)
(opt, flags, extra) = o.parse(sys.argv[1:])
if extra:
o.fatal("no arguments expected")
git.check_repo_or_die()
git.ignore_midx = opt.ignore_midx
mi = git.PackIdxList(git.repo('objects/pack'))
def do_predict(ix):
total = len(ix)
maxdiff = 0
for count,i in enumerate(ix):
prefix = struct.unpack('!Q', i[:8])[0]
expected = prefix * total / (1<<64)
diff = count - expected
maxdiff = max(maxdiff, abs(diff))
print '%d of %d (%.3f%%) ' % (maxdiff, len(ix), maxdiff*100.0/len(ix))
sys.stdout.flush()
assert(count+1 == len(ix))
if opt.predict:
if opt.ignore_midx:
for pack in mi.packs:
do_predict(pack)
else:
do_predict(mi)
else:
# default mode: find longest matching prefix
last = '\0'*20
longmatch = 0
for i in mi:
if i == last:
continue
#assert(str(i) >= last)
pm = _helpers.bitmatch(last, i)
longmatch = max(longmatch, pm)
last = i
print longmatch
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