[PATCH v9 05/10] qcow2_format.py: Dump bitmap directory information

[Andrey Shinkevich]

Read and dump entries from the bitmap directory of QCOW2 image.
It extends the output in the test case #291.

Header extension:
magic                     0x23852875 (Bitmaps)
...

Bitmap name               bitmap-1
bitmap_table_offset       0xf0000
bitmap_table_size         1
flags                     0x2 (['auto'])
type                      1
granularity_bits          16
name_size                 8
extra_data_size           0

Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
---
 tests/qemu-iotests/291.out         | 45 ++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/qcow2_format.py | 47 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 92 insertions(+)

diff --git a/tests/qemu-iotests/291.out b/tests/qemu-iotests/291.out
index 08bfaaa..53a8eeb 100644
--- a/tests/qemu-iotests/291.out
+++ b/tests/qemu-iotests/291.out
@@ -33,6 +33,24 @@ reserved32                0
 bitmap_directory_size     0x40
 bitmap_directory_offset   0x510000
 
+Bitmap name               b1
+bitmap_table_offset       0x4e0000
+bitmap_table_size         1
+flags                     0x0 ([])
+type                      1
+granularity_bits          19
+name_size                 2
+extra_data_size           0
+
+Bitmap name               b2
+bitmap_table_offset       0x500000
+bitmap_table_size         1
+flags                     0x2 (['auto'])
+type                      1
+granularity_bits          16
+name_size                 2
+extra_data_size           0
+
 
 === Bitmap preservation not possible to non-qcow2 ===
 
@@ -98,6 +116,33 @@ reserved32                0
 bitmap_directory_size     0x60
 bitmap_directory_offset   0x520000
 
+Bitmap name               b1
+bitmap_table_offset       0x470000
+bitmap_table_size         1
+flags                     0x0 ([])
+type                      1
+granularity_bits          19
+name_size                 2
+extra_data_size           0
+
+Bitmap name               b2
+bitmap_table_offset       0x490000
+bitmap_table_size         1
+flags                     0x2 (['auto'])
+type                      1
+granularity_bits          16
+name_size                 2
+extra_data_size           0
+
+Bitmap name               b0
+bitmap_table_offset       0x510000
+bitmap_table_size         1
+flags                     0x0 ([])
+type                      1
+granularity_bits          16
+name_size                 2
+extra_data_size           0
+
 
 === Check bitmap contents ===
 
diff --git a/tests/qemu-iotests/qcow2_format.py 
b/tests/qemu-iotests/qcow2_format.py
index 934062a..1438792 100644
--- a/tests/qemu-iotests/qcow2_format.py
+++ b/tests/qemu-iotests/qcow2_format.py
@@ -129,6 +129,53 @@ class Qcow2BitmapExt(Qcow2Struct):
         ('u64', '{:#x}', 'bitmap_directory_offset')
     )
 
+    def __init__(self, fd):
+        super().__init__(fd=fd)
+        self.read_bitmap_directory(fd)
+
+    def read_bitmap_directory(self, fd):
+        fd.seek(self.bitmap_directory_offset)
+        self.bitmap_directory = \
+            [Qcow2BitmapDirEntry(fd) for _ in range(self.nb_bitmaps)]
+
+    def dump(self):
+        super().dump()
+        for entry in self.bitmap_directory:
+            print()
+            entry.dump()
+
+
+class Qcow2BitmapDirEntry(Qcow2Struct):
+
+    fields = (
+        ('u64', '{:#x}', 'bitmap_table_offset'),
+        ('u32', '{}', 'bitmap_table_size'),
+        ('u32', BitmapFlags, 'flags'),
+        ('u8',  '{}', 'type'),
+        ('u8',  '{}', 'granularity_bits'),
+        ('u16', '{}', 'name_size'),
+        ('u32', '{}', 'extra_data_size')
+    )
+
+    def __init__(self, fd):
+        super().__init__(fd=fd)
+        # Seek relative to the current position in the file
+        fd.seek(self.extra_data_size, 1)
+        bitmap_name = fd.read(self.name_size)
+        self.name = bitmap_name.decode('ascii')
+        # Move position to the end of the entry in the directory
+        entry_raw_size = self.bitmap_dir_entry_raw_size()
+        padding = ((entry_raw_size + 7) & ~7) - entry_raw_size
+        fd.seek(padding, 1)
+
+    def bitmap_dir_entry_raw_size(self):
+        return struct.calcsize(self.fmt) + self.name_size + \
+            self.extra_data_size
+
+    def dump(self):
+        print(f'{"Bitmap name":<25} {self.name}')
+        super(Qcow2BitmapDirEntry, self).dump()
+
 
 QCOW2_EXT_MAGIC_BITMAPS = 0x23852875
 
-- 
1.8.3.1