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# (C) 2005 Matt Mackall
# (C) 2005 Canonical Ltd
# based on code by Matt Mackall, hacked by Martin Pool
# mm's code works line-by-line; this just works on byte strings.
# Possibly slower; possibly gives better results for code not
# regularly separated by newlines and anyhow a bit simpler.
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
# TODO: maybe work on files not strings?
# FIXME: doesn't work properly on files without trailing newlines
import difflib
import struct
import sys
import unittest
from cStringIO import StringIO
def linesplit(a):
"""Split into two lists: content and line positions.
This returns (al, ap).
al[i] is the string content of line i of the file, including its
newline (if any).
ap[i] is the byte position in the file where that line starts.
ap[-1] is the byte position of the end of the file (i.e. the
length of the file.)
This transformation allows us to do a line-based diff and then map
back to byte positions.
"""
al, ap = [], []
last = 0
n = a.find("\n") + 1
while n > 0:
ap.append(last)
al.append(a[last:n])
last = n
n = a.find("\n", n) + 1
if last < len(a):
al.append(a[last:])
ap.append(last)
# position at the end
ap.append(len(a))
return (al, ap)
def diff(a, b):
# TODO: Use different splits, perhaps rsync-like, for binary files?
(al, ap) = linesplit(a)
(bl, bp) = linesplit(b)
d = difflib.SequenceMatcher(None, al, bl)
## sys.stderr.write(' ~ real_quick_ratio: %.4f\n' % d.real_quick_ratio())
for o, m, n, s, t in d.get_opcodes():
if o == 'equal': continue
# a[m:n] should be replaced by b[s:t]
if s == t:
yield ap[m], ap[n], ''
else:
yield ap[m], ap[n], ''.join(bl[s:t])
def tobinary(ops):
b = StringIO()
for f in ops:
b.write(struct.pack(">III", f[0], f[1], len(f[2])))
b.write(f[2])
return b.getvalue()
def bdiff(a, b):
return tobinary(diff(a, b))
def patch(t, ops):
last = 0
b = StringIO()
for m, n, r in ops:
b.write(t[last:m])
if r:
b.write(r)
last = n
b.write(t[last:])
return b.getvalue()
def frombinary(b):
bin = StringIO(b)
while True:
p = bin.read(12)
if not p:
break
m, n, l = struct.unpack(">III", p)
if l == 0:
r = ''
else:
r = bin.read(l)
if len(r) != l:
raise Exception("truncated patch data")
yield m, n, r
def bpatch(t, b):
return patch(t, frombinary(b))
class TestDiffPatch(unittest.TestCase):
def doDiffPatch(self, old, new):
diff = bdiff(old, new)
result = bpatch(old, diff)
self.assertEquals(new, result)
def testSimpleDiff(self):
"""Simply add a line at the end"""
self.doDiffPatch('a\nb\n', 'a\nb\nc\n')
def testTrailingLine(self):
"""Test diff that adds an unterminated line.
(Old versions didn't do this properly.)"""
self.doDiffPatch('a\nb\nc\n',
'a\nb\nc\nd')
if __name__ == '__main__':
unittest.main()
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