filemap: fix skip logic

Fixed bug in processing 'skip' parameter:
   don't read input file if end of bmap block is less than skip

Simplified logic of positioning to the start of data inside a
partially skipped bmap block.

(From OE-Core rev: c19f78a0713c8ac9d28b78f86c6d7b96157788f0)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 7 insertions, 4 deletions

diff --git a/scripts/lib/wic/filemap.py b/scripts/lib/wic/filemap.py
index 1f1aacc522..585b7ea84e 100644
--- a/scripts/lib/wic/filemap.py
+++ b/scripts/lib/wic/filemap.py
@@ -545,11 +545,14 @@ def sparse_copy(src_fname, dst_fname, offset=0, skip=0, api=None):
         start = first * fmap.block_size
         end = (last + 1) * fmap.block_size
 
+        if skip >= end:
+            continue
+
         if start < skip < end:
-            fmap._f_image.seek(skip, os.SEEK_SET)
-        else:
-            fmap._f_image.seek(start, os.SEEK_SET)
-        dst_file.seek(offset + start, os.SEEK_SET)
+            start = skip
+
+        fmap._f_image.seek(start, os.SEEK_SET)
+        dst_file.seek(offset + start - skip, os.SEEK_SET)
 
         chunk_size = 1024 * 1024
         to_read = end - start