121 lines
3.5 KiB
Python
121 lines
3.5 KiB
Python
""" Parses ai1wm file header. """
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import collections
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import struct
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from error import Ai1wmError
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from tools import b__, s__
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class Ai1wmHeader(tuple):
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""" Parses an `All-in-One WP Migration` header. """
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SIZE = 4377
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EOF = b'\x00' * SIZE
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_Location = collections.namedtuple('_Location', ['offset', 'size'])
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_LOC_NAME = _Location(0, 255) # File name
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_LOC_SIZE = _Location(255, 14) # File size
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_LOC_TIME = _Location(269, 12) # Last modified time
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_LOC_PATH = _Location(281, 4096) # File path
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def __new__(cls, path=None, name=None, size=None, time=None):
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""" Returns a new instance of the object. """
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if path or name or size or time:
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if not isinstance(path, str) or path == '':
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raise ValueError('<path> must be a nonempty string')
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if not isinstance(name, str) or name == '':
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raise ValueError('<name> must be a nonempty string')
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if not isinstance(size, int) or size < 0:
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raise ValueError('<size> must be a non-negative integer')
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if not isinstance(time, int) or time < 0:
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raise ValueError('<time> must be a non-negative integer')
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return super(Ai1wmHeader, cls).__new__(cls, [path, name, size, time])
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@classmethod
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def unpack(cls, header):
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""" Unpacks a binary header. """
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if len(header) != cls.SIZE:
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raise Ai1wmError('invalid header size')
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if header == cls.EOF:
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return cls()
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return cls(
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path=s__(cls.__extract_field(header, cls._LOC_PATH)),
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name=s__(cls.__extract_field(header, cls._LOC_NAME)),
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size=cls.__extract_int(header, cls._LOC_SIZE),
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time=cls.__extract_int(header, cls._LOC_TIME),
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)
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def pack(self):
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""" Packs to a binary header. """
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attributes, formats, locations = [], '', [
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('name', self._LOC_NAME),
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('size', self._LOC_SIZE),
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('time', self._LOC_TIME),
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('path', self._LOC_PATH),
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]
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for name, location in locations:
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attribute = b__(getattr(self, name))
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if len(attribute) > location.size:
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raise Ai1wmError('{} is too long to pack: {}'.format(name, getattr(self, name)))
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attributes.append(attribute)
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formats += '{}s'.format(location.size)
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return struct.pack(formats, *attributes)
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@property
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def path(self):
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""" Path of the file. """
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return self[0]
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@property
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def name(self):
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""" Name of the file. """
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return self[1]
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@property
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def size(self):
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""" Size of the file. """
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return self[2]
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@property
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def time(self):
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""" Time of the file. """
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return self[3]
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@property
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def eof(self):
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""" Indicates if this is an EOF header. """
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return not any(self)
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@classmethod
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def __extract_field(cls, header, location):
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""" Extracts a header field. """
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try:
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field = struct.unpack_from('{}s'.format(location.size), header, offset=location.offset)[0]
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except struct.error as e:
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raise Ai1wmError('error extracting a header field, error: {}'.format(e))
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return field.rstrip(b'\x00')
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@classmethod
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def __extract_int(cls, header, location):
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""" Extracts an integral header field. """
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try:
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return int(cls.__extract_field(header, location))
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except ValueError:
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raise Ai1wmError('invalid header field')
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