~bialix/bzr/2.0-bug-523069

# (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?

import difflib, sys, struct

from cStringIO import StringIO

def diff(a, b):

    d = difflib.SequenceMatcher(None, a, b)

    ## 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 m, n, ''

        else:

            yield m, n, b[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))