[gnome-continuous-yocto/gnomeostree-3.28-rocko: 6290/8267] filemap: add parameter 'length' to sparse_copy

[Emmanuele Bassi <ebassi src gnome org>]

commit 16562e7672af2c8762d3d089605de48e88905de0
Author: Ed Bartosh <ed bartosh linux intel com>
Date:   Tue Jun 13 14:21:51 2017 +0300

    filemap: add parameter 'length' to sparse_copy
    
    Added parameter 'length' to specify amount of data
    to write into destination file. This is useful when only
    part of source file should be written into destination file.
    
    (From OE-Core rev: cc44e2eb3b5027a3531e6349937a23d73313b3c6)
    
    Signed-off-by: Ed Bartosh <ed bartosh linux intel com>
    Signed-off-by: Richard Purdie <richard purdie linuxfoundation org>

 scripts/lib/wic/filemap.py |   15 ++++++++++++---
 1 files changed, 12 insertions(+), 3 deletions(-)
---
diff --git a/scripts/lib/wic/filemap.py b/scripts/lib/wic/filemap.py
index 585b7ea..8fe302a 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()