# diffhelpers.py - pure Python implementation of diffhelpers.c## Copyright 2009 Matt Mackall <mpm@selenic.com> and others## This software may be used and distributed according to the terms of the# GNU General Public License version 2, incorporated herein by reference. def addlines(fp, hunk, lena, lenb, a, b):    while True:        todoa = lena - len(a)        todob = lenb - len(b)        num = max(todoa, todob)        if num == 0:            break        for i in xrange(num):            s = fp.readline()            c = s[0]            if s == "\\ No newline at end of file\n":                fix_newline(hunk, a, b)                continue            if c == "\n":                # Some patches may be missing the control char                # on empty lines. Supply a leading space.                s = " \n"            hunk.append(s)            if c == "+":                b.append(s[1:])            elif c == "-":                a.append(s)            else:                b.append(s[1:])                a.append(s)    return 0 def fix_newline(hunk, a, b):    l = hunk[-1]    c = l[0]    hline = l[:-1]     if c == " " or c == "+":        b[-1] = l[1:-1]    if c == " " or c == "-":        a[-1] = hline    hunk[-1] = hline    return 0  def testhunk(a, b, bstart):    alen = len(a)    blen = len(b)    if alen > blen - bstart:        return -1    for i in xrange(alen):        if a[i][1:] != b[i + bstart]:            return -1    return 0