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"""
deltastream
~~~~~~~~~~~~~~~~~~~~
A forward or backward stream of delta information used to manage file
versions efficiently
"""
__author__ = 'Benjamin Saller <bcsaller@objectrealms.net>'
__docformat__ = 'restructuredtext'
__copyright__ = 'Copyright ObjectRealms, LLC, 2007'
__license__ = 'The GNU Public License V2+'
import bsdiff
FULL = 1
PATCH = 2
class DeltaStream(object):
"""Record and Reconstruct objects from a forward diff chain. When diff
size/distance from the original is over a threshold we record a
new version in its entirety
"""
def _record(self, old_fn, new_fn):
od = open(old_fn, 'r').read()
nd = open(new_fn, 'r').read()
#XXX: This needs to be done more memory efficiently
patch = bsdiff.Patch(od, nd)
# XXX: again, memory inefficient
if len(str(patch)) < (len(nd) / 2.0):
# The patch is larger than some threshold, we want to
# record a new full version rather than a patch
return FULL, nd
else:
return PATCH, patch
def record(self, old_fn, new_fn):
mode, data = self._record(old_fn, new_fn)
if mode is FULL:
pass
elif mode is PATCH:
pass
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