1 files changed, 12 insertions, 3 deletions

diff --git a/scripts/lib/wic/filemap.py b/scripts/lib/wic/filemap.py
index 585b7ea84e..8fe302ab49 100644
--- a/scripts/lib/wic/filemap.py
+++ b/scripts/lib/wic/filemap.py
@@ -530,7 +530,8 @@ def filemap(image, log=None):
     except ErrorNotSupp:
         return FilemapSeek(image, log)
 
-def sparse_copy(src_fname, dst_fname, offset=0, skip=0, api=None):
+def sparse_copy(src_fname, dst_fname, offset=0, skip=0,
+                length=0, api=None):
     """Efficiently copy sparse file to or into another file."""
     if not api:
         api = filemap
@@ -541,6 +542,7 @@ def sparse_copy(src_fname, dst_fname, offset=0, skip=0, api=None):
         dst_file = open(dst_fname, 'wb')
         dst_file.truncate(os.path.getsize(src_fname))
 
+    written = 0
     for first, last in fmap.get_mapped_ranges(0, fmap.blocks_cnt):
         start = first * fmap.block_size
         end = (last + 1) * fmap.block_size
@@ -561,7 +563,14 @@ def sparse_copy(src_fname, dst_fname, offset=0, skip=0, api=None):
         while read < to_read:
             if read + chunk_size > to_read:
                 chunk_size = to_read - read
-            chunk = fmap._f_image.read(chunk_size)
+            size = chunk_size
+            if length and written + size > length:
+                size = length - written
+            chunk = fmap._f_image.read(size)
             dst_file.write(chunk)
-            read += chunk_size
+            read += size
+            written += size
+            if written == length:
+                dst_file.close()
+                return
     dst_file.close()