292 

   293 def increasingchunks(source, min=1024, max=65536):

   294     '''return no less than min bytes per chunk while data remains,

   295     doubling min after each chunk until it reaches max'''

   296     def log2(x):

   297         if not x:

   298             return 0

   299         i = 0

   300         while x:

   301             x >>= 1

   302             i += 1

   303         return i - 1

   304 

   305     buf = []

   306     blen = 0

   307     for chunk in source:

   308         buf.append(chunk)

   309         blen += len(chunk)

   310         if blen >= min:

   311             if min < max:

   312                 min = min << 1

   313                 nmin = 1 << log2(blen)

   314                 if nmin > min:

   315                     min = nmin

   316                 if min > max:

   317                     min = max

   318             yield ''.join(buf)

   319             blen = 0

   320             buf = []

   321     if buf:

   322         yield ''.join(buf)