qcow2.py: move qcow2 format classes to separate module
We are going to enhance qcow2 format parsing by adding more structure classes. Let's split format parsing from utility code. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-Id: <20200606081806.23897-4-vsementsov@virtuozzo.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy
Eric Blake
parent
16306a7b39
commit
d5262c7124
@ -17,163 +17,11 @@
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#
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#
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import sys
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import sys
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import struct
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import string
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from qcow2_format import (
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class QcowHeaderExtension:
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QcowHeader,
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QcowHeaderExtension
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def __init__(self, magic, length, data):
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)
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if length % 8 != 0:
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padding = 8 - (length % 8)
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data += b"\0" * padding
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self.magic = magic
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self.length = length
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self.data = data
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@classmethod
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def create(cls, magic, data):
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return QcowHeaderExtension(magic, len(data), data)
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class QcowHeader:
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uint32_t = 'I'
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uint64_t = 'Q'
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fields = [
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# Version 2 header fields
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[uint32_t, '%#x', 'magic'],
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[uint32_t, '%d', 'version'],
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[uint64_t, '%#x', 'backing_file_offset'],
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[uint32_t, '%#x', 'backing_file_size'],
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[uint32_t, '%d', 'cluster_bits'],
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[uint64_t, '%d', 'size'],
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[uint32_t, '%d', 'crypt_method'],
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[uint32_t, '%d', 'l1_size'],
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[uint64_t, '%#x', 'l1_table_offset'],
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[uint64_t, '%#x', 'refcount_table_offset'],
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[uint32_t, '%d', 'refcount_table_clusters'],
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[uint32_t, '%d', 'nb_snapshots'],
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[uint64_t, '%#x', 'snapshot_offset'],
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# Version 3 header fields
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[uint64_t, 'mask', 'incompatible_features'],
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[uint64_t, 'mask', 'compatible_features'],
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[uint64_t, 'mask', 'autoclear_features'],
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[uint32_t, '%d', 'refcount_order'],
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[uint32_t, '%d', 'header_length'],
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]
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fmt = '>' + ''.join(field[0] for field in fields)
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def __init__(self, fd):
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buf_size = struct.calcsize(QcowHeader.fmt)
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fd.seek(0)
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buf = fd.read(buf_size)
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header = struct.unpack(QcowHeader.fmt, buf)
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self.__dict__ = dict((field[2], header[i])
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for i, field in enumerate(QcowHeader.fields))
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self.set_defaults()
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self.cluster_size = 1 << self.cluster_bits
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fd.seek(self.header_length)
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self.load_extensions(fd)
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if self.backing_file_offset:
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fd.seek(self.backing_file_offset)
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self.backing_file = fd.read(self.backing_file_size)
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else:
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self.backing_file = None
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def set_defaults(self):
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if self.version == 2:
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self.incompatible_features = 0
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self.compatible_features = 0
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self.autoclear_features = 0
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self.refcount_order = 4
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self.header_length = 72
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def load_extensions(self, fd):
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self.extensions = []
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if self.backing_file_offset != 0:
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end = min(self.cluster_size, self.backing_file_offset)
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else:
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end = self.cluster_size
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while fd.tell() < end:
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(magic, length) = struct.unpack('>II', fd.read(8))
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if magic == 0:
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break
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else:
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padded = (length + 7) & ~7
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data = fd.read(padded)
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self.extensions.append(QcowHeaderExtension(magic, length,
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data))
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def update_extensions(self, fd):
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fd.seek(self.header_length)
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extensions = self.extensions
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extensions.append(QcowHeaderExtension(0, 0, b""))
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for ex in extensions:
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buf = struct.pack('>II', ex.magic, ex.length)
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fd.write(buf)
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fd.write(ex.data)
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if self.backing_file is not None:
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self.backing_file_offset = fd.tell()
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fd.write(self.backing_file)
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if fd.tell() > self.cluster_size:
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raise Exception("I think I just broke the image...")
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def update(self, fd):
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header_bytes = self.header_length
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self.update_extensions(fd)
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fd.seek(0)
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header = tuple(self.__dict__[f] for t, p, f in QcowHeader.fields)
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buf = struct.pack(QcowHeader.fmt, *header)
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buf = buf[0:header_bytes-1]
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fd.write(buf)
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def dump(self):
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for f in QcowHeader.fields:
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value = self.__dict__[f[2]]
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if f[1] == 'mask':
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bits = []
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for bit in range(64):
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if value & (1 << bit):
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bits.append(bit)
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value_str = str(bits)
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else:
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value_str = f[1] % value
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print("%-25s" % f[2], value_str)
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print("")
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def dump_extensions(self):
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for ex in self.extensions:
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data = ex.data[:ex.length]
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if all(c in string.printable.encode('ascii') for c in data):
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data = "'%s'" % data.decode('ascii')
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else:
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data = "<binary>"
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print("Header extension:")
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print("%-25s %#x" % ("magic", ex.magic))
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print("%-25s %d" % ("length", ex.length))
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print("%-25s %s" % ("data", data))
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print("")
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def cmd_dump_header(fd):
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def cmd_dump_header(fd):
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173
tests/qemu-iotests/qcow2_format.py
Normal file
173
tests/qemu-iotests/qcow2_format.py
Normal file
@ -0,0 +1,173 @@
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# Library for manipulations with qcow2 image
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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#
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import struct
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import string
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class QcowHeaderExtension:
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def __init__(self, magic, length, data):
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if length % 8 != 0:
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padding = 8 - (length % 8)
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data += b"\0" * padding
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self.magic = magic
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self.length = length
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self.data = data
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@classmethod
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def create(cls, magic, data):
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return QcowHeaderExtension(magic, len(data), data)
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class QcowHeader:
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uint32_t = 'I'
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uint64_t = 'Q'
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fields = [
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# Version 2 header fields
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[uint32_t, '%#x', 'magic'],
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[uint32_t, '%d', 'version'],
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[uint64_t, '%#x', 'backing_file_offset'],
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[uint32_t, '%#x', 'backing_file_size'],
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[uint32_t, '%d', 'cluster_bits'],
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[uint64_t, '%d', 'size'],
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[uint32_t, '%d', 'crypt_method'],
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[uint32_t, '%d', 'l1_size'],
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[uint64_t, '%#x', 'l1_table_offset'],
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[uint64_t, '%#x', 'refcount_table_offset'],
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[uint32_t, '%d', 'refcount_table_clusters'],
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[uint32_t, '%d', 'nb_snapshots'],
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[uint64_t, '%#x', 'snapshot_offset'],
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# Version 3 header fields
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[uint64_t, 'mask', 'incompatible_features'],
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[uint64_t, 'mask', 'compatible_features'],
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[uint64_t, 'mask', 'autoclear_features'],
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[uint32_t, '%d', 'refcount_order'],
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[uint32_t, '%d', 'header_length'],
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]
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fmt = '>' + ''.join(field[0] for field in fields)
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def __init__(self, fd):
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buf_size = struct.calcsize(QcowHeader.fmt)
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fd.seek(0)
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buf = fd.read(buf_size)
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header = struct.unpack(QcowHeader.fmt, buf)
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self.__dict__ = dict((field[2], header[i])
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for i, field in enumerate(QcowHeader.fields))
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self.set_defaults()
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self.cluster_size = 1 << self.cluster_bits
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fd.seek(self.header_length)
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self.load_extensions(fd)
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if self.backing_file_offset:
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fd.seek(self.backing_file_offset)
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self.backing_file = fd.read(self.backing_file_size)
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else:
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self.backing_file = None
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def set_defaults(self):
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if self.version == 2:
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self.incompatible_features = 0
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self.compatible_features = 0
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self.autoclear_features = 0
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self.refcount_order = 4
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self.header_length = 72
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def load_extensions(self, fd):
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self.extensions = []
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if self.backing_file_offset != 0:
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end = min(self.cluster_size, self.backing_file_offset)
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else:
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end = self.cluster_size
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while fd.tell() < end:
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(magic, length) = struct.unpack('>II', fd.read(8))
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if magic == 0:
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break
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else:
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padded = (length + 7) & ~7
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data = fd.read(padded)
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self.extensions.append(QcowHeaderExtension(magic, length,
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data))
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def update_extensions(self, fd):
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fd.seek(self.header_length)
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extensions = self.extensions
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extensions.append(QcowHeaderExtension(0, 0, b""))
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for ex in extensions:
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buf = struct.pack('>II', ex.magic, ex.length)
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fd.write(buf)
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fd.write(ex.data)
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if self.backing_file is not None:
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self.backing_file_offset = fd.tell()
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fd.write(self.backing_file)
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if fd.tell() > self.cluster_size:
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raise Exception("I think I just broke the image...")
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def update(self, fd):
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header_bytes = self.header_length
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self.update_extensions(fd)
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fd.seek(0)
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header = tuple(self.__dict__[f] for t, p, f in QcowHeader.fields)
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buf = struct.pack(QcowHeader.fmt, *header)
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buf = buf[0:header_bytes-1]
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fd.write(buf)
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def dump(self):
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for f in QcowHeader.fields:
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value = self.__dict__[f[2]]
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if f[1] == 'mask':
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bits = []
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for bit in range(64):
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if value & (1 << bit):
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bits.append(bit)
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value_str = str(bits)
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else:
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value_str = f[1] % value
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print("%-25s" % f[2], value_str)
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print("")
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def dump_extensions(self):
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for ex in self.extensions:
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data = ex.data[:ex.length]
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if all(c in string.printable.encode('ascii') for c in data):
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data = "'%s'" % data.decode('ascii')
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else:
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data = "<binary>"
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print("Header extension:")
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print("%-25s %#x" % ("magic", ex.magic))
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print("%-25s %d" % ("length", ex.length))
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print("%-25s %s" % ("data", data))
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print("")
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