generate version 2 blockimgdiff files

Generate version 2 of the block_image_update transfer list format.
This improves patch size by a different strategy for dealing with
out-of-order transfers.  If transfer A must be done before transfer B
due to B overwriting A's source but we want to do B before A, we
resolve the conflict by:

  - before B is executed, we save ("stash") the overlapping region (ie
    the blocks B will overwrite that A wants to read)

  - when A is executed, it will read those parts of source data from
    the stash rather than from the image.

This reverses the ordering constraint; with these additions now B
*must* go before A.  The implementation of the stash is left up to the
code that executes the transfer list to apply the patch; it could hold
stashed data in RAM or on a scratch disk such as /cache, if available.

The code retains the ability to build a version 1 block image patch;
it's needed for processing older target-files.

Change-Id: Ia9aa0bd45d5dc3ef7c5835e483b1b2ead10135fe

tools/releasetools/rangelib.py

@@ -173,3 +173,39 @@ class RangeSet(object):
       else:
         total -= p
     return total
+
+  def map_within(self, other):
+    """'other' should be a subset of 'self'.  Returns a RangeSet
+    representing what 'other' would get translated to if the integers
+    of 'self' were translated down to be contiguous starting at zero.
+
+    >>> RangeSet.parse("0-9").map_within(RangeSet.parse("3-4")).to_string()
+    '3-4'
+    >>> RangeSet.parse("10-19").map_within(RangeSet.parse("13-14")).to_string()
+    '3-4'
+    >>> RangeSet.parse("10-19 30-39").map_within(
+    ...     RangeSet.parse("17-19 30-32")).to_string()
+    '7-12'
+    >>> RangeSet.parse("10-19 30-39").map_within(
+    ...     RangeSet.parse("12-13 17-19 30-32")).to_string()
+    '2-3 7-12'
+    """
+
+    out = []
+    offset = 0
+    start = None
+    for p, d in heapq.merge(zip(self.data, itertools.cycle((-5, +5))),
+                            zip(other.data, itertools.cycle((-1, +1)))):
+      if d == -5:
+        start = p
+      elif d == +5:
+        offset += p-start
+        start = None
+      else:
+        out.append(offset + p - start)
+    return RangeSet(data=out)
+
+
+if __name__ == "__main__":
+  import doctest
+  doctest.testmod()