03.07.2020 16:13, Andrey Shinkevich wrote:
There are two ways to initialize a class derived from Qcow2Struct:
1. Pass a block of binary data to the constructor.
2. Pass the file descriptor to allow reading the file from constructor.
Let's change the Qcow2BitmapExt initialization method from 1 to 2 to
support a scattered reading in the initialization chain.
The implementation comes with the patch that follows.
Suggested-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
Signed-off-by: Andrey Shinkevich <andrey.shinkev...@virtuozzo.com>
---
tests/qemu-iotests/qcow2_format.py | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/tests/qemu-iotests/qcow2_format.py
b/tests/qemu-iotests/qcow2_format.py
index 2f3681b..1435e34 100644
--- a/tests/qemu-iotests/qcow2_format.py
+++ b/tests/qemu-iotests/qcow2_format.py
@@ -63,7 +63,8 @@ class Qcow2StructMeta(type):
class Qcow2Struct(metaclass=Qcow2StructMeta):
- """Qcow2Struct: base class for qcow2 data structures
+ """
+ Qcow2Struct: base class for qcow2 data structures
Unrelated chunk. And why?
Successors should define fields class variable, which is: list of tuples,
each of three elements:
@@ -113,6 +114,9 @@ class Qcow2BitmapExt(Qcow2Struct):
('u64', '{:#x}', 'bitmap_directory_offset')
)
+ def __init__(self, fd):
+ super().__init__(fd=fd)
this does nothing. We inherit the __init__ of super class, no need to define it
just to call same __init__.
+
QCOW2_EXT_MAGIC_BITMAPS = 0x23852875
@@ -173,7 +177,13 @@ class QcowHeaderExtension(Qcow2Struct):
self.data_str = data_str
if self.magic == QCOW2_EXT_MAGIC_BITMAPS:
- self.obj = Qcow2BitmapExt(data=self.data)
+ assert fd is not None
+ position = fd.tell()
+ # Step back to reread data
This definitely shows that we are doing something wrong
+ padded = (self.length + 7) & ~7
+ fd.seek(-padded, 1)
+ self.obj = Qcow2BitmapExt(fd=fd)
+ fd.seek(position)
else:
self.obj = None
--
Best regards,
Vladimir
