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qcow2_format.py: use strings to specify c-type of struct fields

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We are going to move field-parsing to super-class, this will be simpler
with simple string specifiers instead of variables.

For some reason, python doesn't allow the definition of ctypes variable
in the class alongside fields: it would not be available then for use
by the 'for' operator. Don't worry: ctypes will be moved to metaclass
soon.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Message-Id: <20200606081806.23897-8-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2020-06-06 11:18:00 +03:00 committed by Eric Blake
parent 621ca4988a
commit 5432a0db52
1 changed files with 28 additions and 22 deletions
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50
tests/qemu-iotests/qcow2_format.py
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@ -34,36 +34,42 @@ class QcowHeaderExtension:
return QcowHeaderExtension(magic, len(data), data)
class QcowHeader:
# Mapping from c types to python struct format
ctypes = {
'u8': 'B',
'u16': 'H',
'u32': 'I',
'u64': 'Q'
}
uint32_t = 'I'
uint64_t = 'Q'
class QcowHeader:
fields = (
# Version 2 header fields
(uint32_t, '{:#x}', 'magic'),
(uint32_t, '{}', 'version'),
(uint64_t, '{:#x}', 'backing_file_offset'),
(uint32_t, '{:#x}', 'backing_file_size'),
(uint32_t, '{}', 'cluster_bits'),
(uint64_t, '{}', 'size'),
(uint32_t, '{}', 'crypt_method'),
(uint32_t, '{}', 'l1_size'),
(uint64_t, '{:#x}', 'l1_table_offset'),
(uint64_t, '{:#x}', 'refcount_table_offset'),
(uint32_t, '{}', 'refcount_table_clusters'),
(uint32_t, '{}', 'nb_snapshots'),
(uint64_t, '{:#x}', 'snapshot_offset'),
('u32', '{:#x}', 'magic'),
('u32', '{}', 'version'),
('u64', '{:#x}', 'backing_file_offset'),
('u32', '{:#x}', 'backing_file_size'),
('u32', '{}', 'cluster_bits'),
('u64', '{}', 'size'),
('u32', '{}', 'crypt_method'),
('u32', '{}', 'l1_size'),
('u64', '{:#x}', 'l1_table_offset'),
('u64', '{:#x}', 'refcount_table_offset'),
('u32', '{}', 'refcount_table_clusters'),
('u32', '{}', 'nb_snapshots'),
('u64', '{:#x}', 'snapshot_offset'),
# Version 3 header fields
(uint64_t, 'mask', 'incompatible_features'),
(uint64_t, 'mask', 'compatible_features'),
(uint64_t, 'mask', 'autoclear_features'),
(uint32_t, '{}', 'refcount_order'),
(uint32_t, '{}', 'header_length'),
('u64', 'mask', 'incompatible_features'),
('u64', 'mask', 'compatible_features'),
('u64', 'mask', 'autoclear_features'),
('u32', '{}', 'refcount_order'),
('u32', '{}', 'header_length'),
)
fmt = '>' + ''.join(field[0] for field in fields)
fmt = '>' + ''.join(ctypes[f[0]] for f in fields)
def __init__(self, fd):