~bzr-pqm/bzr/bzr.dev

# Copyright (C) 2004, 2005 by Canonical Ltd

# 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

# mbp: "you know that thing where cvs gives you conflict markers?"

# s: "i hate that."

def intersect(ra, rb):

    """Given two ranges return the range where they intersect or None.

    >>> intersect((0, 10), (0, 6))

    (0, 6)

    >>> intersect((0, 10), (5, 15))

    (5, 10)

    >>> intersect((0, 10), (10, 15))

    >>> intersect((0, 9), (10, 15))

    >>> intersect((0, 9), (7, 15))

    (7, 9)

    """

    assert ra[0] <= ra[1]

    assert rb[0] <= rb[1]

    sa = max(ra[0], rb[0])

    sb = min(ra[1], rb[1])

    if sa < sb:

        return sa, sb

    else:

        return None

def threeway(baseline, aline, bline):

    if baseline == aline:

        return bline

    elif baseline == bline:

        return aline

    else:

        return [aline, bline]

class Merge3(object):

    """3-way merge of texts.

    Given BASE, OTHER, THIS, tries to produce a combined text

    incorporating the changes from both BASE->OTHER and BASE->THIS.

    All three will typically be sequences of lines."""

    def __init__(self, base, a, b):

        self.base = base

        self.a = a

        self.b = b

        from difflib import SequenceMatcher

        self.a_ops = SequenceMatcher(None, base, a).get_opcodes()

        self.b_ops = SequenceMatcher(None, base, b).get_opcodes()

    def merge_regions(self):

        """Return sequences of matching and conflicting regions.

        This returns tuples, where the first value says what kind we

        have:

        'unchanged', start, end

             Take a region of base[start:end]

        'a', start, end

             Non-clashing insertion from a[start:end]

        Method is as follows:

        The two sequences align only on regions which match the base

        and both descendents.  These are found by doing a two-way diff

        of each one against the base, and then finding the

        intersections between those regions.  These "sync regions"

        are by definition unchanged in both and easily dealt with.

        The regions in between can be in any of three cases:

        conflicted, or changed on only one side.

        """

        # section a[0:ia] has been disposed of, etc

        iz = ia = ib = 0

        for zmatch, zend, amatch, aend, bmatch, bend in self.find_sync_regions():

            matchlen = zend - zmatch

            assert matchlen >= 0

            assert matchlen == (aend - amatch)

            assert matchlen == (bend - bmatch)

            if amatch > ia:   # or bmatch > ib:

                # got an unmatched region; work out if either

                # alternative is the same as the base

                # kludge: return the whole thing as inserted into A

                yield 'a', ia, amatch

                ia = amatch

            if matchlen > 0:

                assert ia == amatch

                assert ib == bmatch

                assert iz == zmatch

                yield 'unchanged', zmatch, zend

                iz = zend

                ia = aend

                ib = bend

    def find_sync_regions(self):

        """Return a list of sync regions, where both descendents match the base.

        Generates a list of (base1, base2, a1, a2, b1, b2).  There is

        always a zero-length sync region at the end of all the files.

        """

        from difflib import SequenceMatcher

        aiter = iter(SequenceMatcher(None, self.base, self.a).get_matching_blocks())

        biter = iter(SequenceMatcher(None, self.base, self.b).get_matching_blocks())

        abase, amatch, alen = aiter.next()

        bbase, bmatch, blen = biter.next()

        while aiter and biter:

            # there is an unconflicted block at i; how long does it

            # extend?  until whichever one ends earlier.

            i = intersect((abase, abase+alen), (bbase, bbase+blen))

            if i:

                intbase = i[0]

                intend = i[1]

                intlen = intend - intbase

                # found a match of base[i[0], i[1]]; this may be less than

                # the region that matches in either one

                assert intlen <= alen

                assert intlen <= blen

                assert abase <= intbase

                assert bbase <= intbase

                asub = amatch + (intbase - abase)

                bsub = bmatch + (intbase - bbase)

                aend = asub + intlen

                bend = bsub + intlen

                assert self.base[intbase:intend] == self.a[asub:aend], \

                       (self.base[intbase:intend], self.a[asub:aend])

                assert self.base[intbase:intend] == self.b[bsub:bend]

                yield (intbase, intend,

                       asub, aend,

                       bsub, bend)

            # advance whichever one ends first in the base text

            if (abase + alen) < (bbase + blen):

                abase, amatch, alen = aiter.next()

            else:

                bbase, bmatch, blen = biter.next()

        intbase = len(self.base)

        abase = len(self.a)

        bbase = len(self.b)

        yield (intbase, intbase, abase, abase, bbase, bbase)

    def find_unconflicted(self):

        """Return a list of ranges in base that are not conflicted."""

        from difflib import SequenceMatcher

        am = SequenceMatcher(None, self.base, self.a).get_matching_blocks()

        bm = SequenceMatcher(None, self.base, self.b).get_matching_blocks()

        unc = []

        while am and bm:

            # there is an unconflicted block at i; how long does it

            # extend?  until whichever one ends earlier.

            a1 = am[0][0]

            a2 = a1 + am[0][2]

            b1 = bm[0][0]

            b2 = b1 + bm[0][2]

            i = intersect((a1, a2), (b1, b2))

            if i:

                unc.append(i)

            if a2 < b2:

                del am[0]

            else:

                del bm[0]

        return unc