[gnome-continuous-yocto/gnomeostree-3.28-rocko: 6304/8267] filemap: calculate dst size correctly

[Emmanuele Bassi <ebassi src gnome org>]

commit d5e3c917032a59bbe93969ed0bbb4659089dfec4
Author: Ed Bartosh <ed bartosh linux intel com>
Date:   Tue Jun 13 14:22:05 2017 +0300

    filemap: calculate dst size correctly
    
    Fixed calculation of the dst file size using skip, seek and
    length parameters. Current code does it incorrectly which
    causes sparse_copy API to create unnecessary big output files.
    
    (From OE-Core rev: e6d709a6382e4b913612f597e66ad07b0e351d5f)
    
    Signed-off-by: Ed Bartosh <ed bartosh linux intel com>
    Signed-off-by: Richard Purdie <richard purdie linuxfoundation org>

 scripts/lib/wic/filemap.py |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/scripts/lib/wic/filemap.py b/scripts/lib/wic/filemap.py
index 764dbbe..6d11355 100644
--- a/scripts/lib/wic/filemap.py
+++ b/scripts/lib/wic/filemap.py
@@ -549,7 +549,11 @@ def sparse_copy(src_fname, dst_fname, skip=0, seek=0,
         dst_file = open(dst_fname, 'r+b')
     except IOError:
         dst_file = open(dst_fname, 'wb')
-        dst_file.truncate(os.path.getsize(src_fname))
+        if length:
+            dst_size = length + seek
+        else:
+            dst_size = os.path.getsize(src_fname) + seek - skip
+        dst_file.truncate(dst_size)
 
     written = 0
     for first, last in fmap.get_mapped_ranges(0, fmap.blocks_cnt):