releasetools: Disable using imgdiff for squashfs.

We use imgdiff to handle files in zip format (e.g. jar/zip/apk) for
higher compression ratio.

For system/vendor in squashfs, a) all files are compressed in LZ4
format; b) we use 4096-byte block size in their sparse images, but the
files in squashfs may not be laid out as 4K-aligned. So the blocks for
a given file as listed in block map may not form a valid zip file, which
may fail the patch generation with imgdiff.

Disable using imgdiff for squashfs images, and use bsdiff instead.

Bug: 22322817
Change-Id: Ie76aa4cece5c9d38cb1d1a34c505a4a8f37512d3

tools/releasetools/blockimgdiff.py

@@ -261,7 +261,8 @@ class HeapItem(object):
 # original image.
 
 class BlockImageDiff(object):
-  def __init__(self, tgt, src=None, threads=None, version=4):
+  def __init__(self, tgt, src=None, threads=None, version=4,
+               disable_imgdiff=False):
     if threads is None:
       threads = multiprocessing.cpu_count() // 2
       if threads == 0:
@@ -274,6 +275,7 @@ class BlockImageDiff(object):
     self._max_stashed_size = 0
     self.touched_src_ranges = RangeSet()
     self.touched_src_sha1 = None
+    self.disable_imgdiff = disable_imgdiff
 
     assert version in (1, 2, 3, 4)
 
@@ -714,6 +716,7 @@ class BlockImageDiff(object):
             # produces significantly smaller patches than bsdiff).
             # This is permissible if:
             #
+            #  - imgdiff is not disabled, and
             #  - the source and target files are monotonic (ie, the
             #    data is stored with blocks in increasing order), and
             #  - we haven't removed any blocks from the source set.
@@ -723,7 +726,7 @@ class BlockImageDiff(object):
             # zip file (plus possibly extra zeros in the last block),
             # which is what imgdiff needs to operate.  (imgdiff is
             # fine with extra zeros at the end of the file.)
-            imgdiff = (xf.intact and
+            imgdiff = (not self.disable_imgdiff and xf.intact and
                        xf.tgt_name.split(".")[-1].lower()
                        in ("apk", "jar", "zip"))
             xf.style = "imgdiff" if imgdiff else "bsdiff"