view mercurial/ancestor.py @ 5846:02884e56c217

New extension to support problematic MBCS on Windows.

The aim of this extension is to clear the problem related to having
0x5c in 2nd byte of encoded bytes.  So this extension is usefull for:
 * Japanese Windows user shift_jis encoding.
 * Chinese Windows user using big5 encoding.

To use this extension, simply enable it without any customization.

Note that some important python built-in functions and mercurial
functions are altered for this extension to convert argument if need
to handle MBCS.

# ancestor.py - generic DAG ancestor algorithm for mercurial
#
# Copyright 2006 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.

import heapq

def ancestor(a, b, pfunc):
    """
    return the least common ancestor of nodes a and b or None if there
    is no such ancestor.

    pfunc must return a list of parent vertices
    """

    if a == b:
        return a

    # find depth from root of all ancestors
    visit = [a, b]
    depth = {}
    while visit:
        vertex = visit[-1]
        pl = pfunc(vertex)
        if not pl:
            depth[vertex] = 0
            visit.pop()
        else:
            for p in pl:
                if p == a or p == b: # did we find a or b as a parent?
                    return p # we're done
                if p not in depth:
                    visit.append(p)
            if visit[-1] == vertex:
                depth[vertex] = min([depth[p] for p in pl]) - 1
                visit.pop()

    # traverse ancestors in order of decreasing distance from root
    def ancestors(vertex):
        h = [(depth[vertex], vertex)]
        seen = {}
        while h:
            d, n = heapq.heappop(h)
            if n not in seen:
                seen[n] = 1
                yield (d, n)
                for p in pfunc(n):
                    heapq.heappush(h, (depth[p], p))

    def generations(vertex):
        sg, s = None, {}
        for g, v in ancestors(vertex):
            if g != sg:
                if sg:
                    yield sg, s
                sg, s = g, {v:1}
            else:
                s[v] = 1
        yield sg, s

    x = generations(a)
    y = generations(b)
    gx = x.next()
    gy = y.next()

    # increment each ancestor list until it is closer to root than
    # the other, or they match
    try:
        while 1:
            if gx[0] == gy[0]:
                for v in gx[1]:
                    if v in gy[1]:
                        return v
                gy = y.next()
                gx = x.next()
            elif gx[0] > gy[0]:
                gy = y.next()
            else:
                gx = x.next()
    except StopIteration:
        return None