2243 def increasingwindows(windowsize=8, sizelimit=512):

  2244     while True:

  2245         yield windowsize

  2246         if windowsize < sizelimit:

  2247             windowsize *= 2

  2248 

  2249 

  2250 def walkchangerevs(repo, revs, makefilematcher, prepare):

  2251     '''Iterate over files and the revs in a "windowed" way.

  2252 

  2253     Callers most commonly need to iterate backwards over the history

  2254     in which they are interested. Doing so has awful (quadratic-looking)

  2255     performance, so we use iterators in a "windowed" way.

  2256 

  2257     We walk a window of revisions in the desired order.  Within the

  2258     window, we first walk forwards to gather data, then in the desired

  2259     order (usually backwards) to display it.

  2260 

  2261     This function returns an iterator yielding contexts. Before

  2262     yielding each context, the iterator will first call the prepare

  2263     function on each context in the window in forward order.'''

  2264 

  2265     if not revs:

  2266         return []

  2267     change = repo.__getitem__

  2268 

  2269     def iterate():

  2270         it = iter(revs)

  2271         stopiteration = False

  2272         for windowsize in increasingwindows():

  2273             nrevs = []

  2274             for i in pycompat.xrange(windowsize):

  2275                 rev = next(it, None)

  2276                 if rev is None:

  2277                     stopiteration = True

  2278                     break

  2279                 nrevs.append(rev)

  2280             for rev in sorted(nrevs):

  2281                 ctx = change(rev)

  2282                 prepare(ctx, makefilematcher(ctx))

  2283             for rev in nrevs:

  2284                 yield change(rev)

  2285 

  2286             if stopiteration:

  2287                 break

  2288 

  2289     return iterate()

  2290 

  2291