Updated extractar
- removed `on_setattr` argument in attr.ib() call for `name` attribute in `class@ArchiveInfo`. - update docstring for class@Archive. - if `file=` provided with None, ValueError is raised instead of RuntimeError. - changed attributes of class@Archive to be private. - added setattr dunder method similar to class@ArchiveInfo, but all attributes are defined as constant. Any attempt to modify constants throws an AttributeError - added property for attribute `__file` in class@Archive. - refactored code to use os.path instead of pathlib. Pathlib was restrictive on not allowing byte-like strings, and is an inappropriate module for the task (os is just simpler). - ensured that writing the byte contents from an archive to a new file occurs within a try-except statement, and raises an IOError if the write fails in some way due to IO. - other minor amendments.
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117
extractar.py
117
extractar.py
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@ -30,7 +30,6 @@
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import os
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import struct
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import textwrap
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import pathlib
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from typing import Any
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import attr
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@ -59,8 +58,9 @@ class ArchiveBufferReadError(IndexError):
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Debian binary package entry information. Exception is of type IndexError.
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"""
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@attr.s(slots=True)
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class ArchiveInfo(object):
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class ArchiveInfo:
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"""
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Information on a file in an archive.
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@ -79,7 +79,7 @@ class ArchiveInfo(object):
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the same name are present; if you change the `name` attribute, the initial
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file will be extracted with the new name (and new metadata).
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"""
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name: bytes = attr.ib(converter=lambda s: _utf8(s).rstrip(b' '), on_setattr=attr.setters.NO_OP)
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name: bytes = attr.ib(converter=lambda s: _utf8(s).rstrip(b' '))
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size: int = attr.ib(converter=int)
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mtime: int = attr.ib(converter=int)
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perms: int = attr.ib(converter=lambda x: int(x, 8))
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@ -88,6 +88,29 @@ class ArchiveInfo(object):
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offset: int = attr.ib(converter=int, default=0)
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def __setattr__(self, __name: str, __value: Any) -> None:
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"""
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Custom setattr dunder method to create strict immutability over certain attributes of a class. Any attributes
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which may be mutable should be handled appropriately.
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"""
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# |------ immutable ------| |---- mutable ----|
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if not hasattr(self, __name) or __name == "offset":
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object.__setattr__(self, __name, __value)
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def __repr__(self) -> str:
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return textwrap.dedent('''\
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{7}: ({0})
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name: {0}
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size: {1}
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mtime: {2}
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perms: {3}
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uid: {4}
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gid: {5}
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offset: {6}\n'''.format(self.name, self.size, self.mtime, self.perms, self.uid, self.gid, self.offset,
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self.__class__))
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@classmethod
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def frombuffer(cls, buffer):
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"""
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@ -111,33 +134,14 @@ class ArchiveInfo(object):
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return cls(name=name, size=size, mtime=mtime, perms=perms, uid=uid, gid=gid)
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def __setattr__(self, __name: str, __value: Any) -> None:
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"""
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Custom setattr dunder method to create strict immutability over certain attributes of a class. Any attributes
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which may be mutable should be handled appropriately.
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"""
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# |------ immutable ------| |---- mutable ----|
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if not hasattr(self, __name) or __name == "offset":
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object.__setattr__(self, __name, __value)
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def __repr__(self) -> str:
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return textwrap.dedent('''\
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{7}: ({0})
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_name: {0}
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size: {1}
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mtime: {2}
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perms: {3}
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uid: {4}
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gid: {5}
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offset: {6}\n'''.format(self.name, self.size, self.mtime, self.perms, self.uid, self.gid, self.offset,
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self.__class__))
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class Archive:
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"""
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An UNIX ar archive.
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An archive manager for extracting files which have been stored in Debian package binaries using the common format.
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Replaces the extraction method of the `ar` Unix command, to be used on read-only archives.
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Initialise the class with a string path to a file, and invoke the `open()` method to load the archive into memory.
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After this, the other methods of the class may be used to act upon the archived information appropriately, such as
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extracting entries from the archive.
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"""
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def __init__(self, file: str):
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"""
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@ -146,11 +150,27 @@ class Archive:
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Initialisation is lazy. Please invoke the `open()` method to load the archive into memory.
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"""
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if file is None:
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raise RuntimeError("File must not be None.")
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raise ValueError("File must not be None.")
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self._file = pathlib.Path(file)
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self._mapping: dict[bytes, ArchiveInfo] = {}
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self.__ar_contents: bytes
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self.__file = os.path.realpath(file)
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self.__mapping: dict[bytes, ArchiveInfo] = {}
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self.__ArByteStream: bytes
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def __setattr__(self, __name: str, __value: Any) -> None:
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"""
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Custom setattr dunder method to create strict immutability over certain attributes of a class. Any attributes
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which may be mutable should be handled appropriately.
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"""
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if not hasattr(self, __name):
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object.__setattr__(self, __name, __value)
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else:
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raise AttributeError(f"The attribute {__name} is private and not intended to be modified.")
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@property
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def file(self):
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return str(self.__file)
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def open(self):
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@ -166,19 +186,19 @@ class Archive:
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setattr(self, '__instance__', self)
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# firstly, ensure that the path exists on the system
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if not self._file.exists():
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raise FileNotFoundError(f"The specified file: {self._file}, could not be found.")
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if not os.path.exists(self.__file) :#self.__file.exists():
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raise FileNotFoundError(f"The specified file: {self.__file}, could not be found.")
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# secondly, ensure that the path is of type file, and accessible for reading
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if not pathlib.Path(self._file).is_file() and os.access(self._file, mode=os.R_OK):
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raise FileExistsError(f"The specified file: {self._file}, is either a directory or not readable.")
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if not os.path.isfile(self.__file) and os.access(self.__file, mode=os.R_OK):
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raise FileExistsError(f"The specified file: {self.__file}, is either a directory or not readable.")
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# @Ethan: just never trust I/O operations fully
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try:
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# open the file in binary read-mode
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with open(self._file, 'rb') as fp:
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with open(self.__file, 'rb') as fp:
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# we want to read and dump everything into memory.
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self.__ar_contents = fp.read()
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self.__ArByteStream = fp.read()
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except IOError as err:
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raise RuntimeError("There was an issue reading the archive file.") from err
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@ -199,12 +219,12 @@ class Archive:
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):
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raise RuntimeError(self, "has been partially initialised. Please invoke Archive@open(...) first.")
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CONTENT_LENGTH = len(self.__ar_contents)
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CONTENT_LENGTH = len(self.__ArByteStream)
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if CONTENT_LENGTH < 8:
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raise ArchiveMagicBytesError("The loaded archive size is less than the magic bytes.")
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# check the magic bytes
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if self.__ar_contents[:8] != b'!<arch>\n':
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if self.__ArByteStream[:8] != b'!<arch>\n':
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raise ArchiveMagicBytesError("Invalid archive signature")
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# define some variable constants
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@ -214,7 +234,7 @@ class Archive:
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pos = 8
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while pos != CONTENT_LENGTH: # keep going until we reach the end of the content
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# read in 60 bytes of data (length of headers in Debian archive)
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buffer = self.__ar_contents[pos:pos+HEADER_LENGTH]
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buffer = self.__ArByteStream[pos:pos+HEADER_LENGTH]
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# check to ensure that the archive isn't truncated
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if len(buffer) != HEADER_LENGTH:
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raise ArchiveBufferReadError(
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@ -226,7 +246,7 @@ class Archive:
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member.offset = pos
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# add our entry to the mappings dict (key: name of member, value: `:class:@ArchiveInfo`)
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self._mapping[member.name.removesuffix(b'/')] = member
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self.__mapping[member.name.removesuffix(b'/')] = member
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# move the position in the content by the size of the member (with +1 if odd size)
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pos += HEADER_LENGTH + member.size + (1 if member.size % 2 != 0 else 0)
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@ -242,8 +262,8 @@ class Archive:
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@Returns: ArchiveInfo
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"""
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if _utf8(member) in self._mapping:
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return self._mapping[_utf8(member)]
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if _utf8(member) in self.__mapping:
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return self.__mapping[_utf8(member)]
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return ArchiveInfo(b"", 0, 0, 0, 0, 0)
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@ -273,9 +293,12 @@ class Archive:
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# write out the specific content of an archive member
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pos = member.offset + 60
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# @TODO: put in try cus IO be IO lmao
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with open(path, 'wb') as fp:
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fp.write(self.__ar_contents[pos:pos+member.size])
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try:
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with open(self.__file, 'wb') as fp:
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fp.write(self.__ArByteStream[pos:pos+member.size])
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except IOError:
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raise IOError(f"There was an issue when writing the bytes to file: {path}.\n",
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"Please be wary of any mangled or corrupt files.")
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def extractall(self, path: str | bytes = ''):
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@ -293,5 +316,5 @@ class Archive:
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raise RuntimeError(self, "has been partially initialised. Please invoke Archive@open(...) first.")
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# iterate over all members in the mapping
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for name in self._mapping.keys():
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for name in self.__mapping.keys():
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self.extract(name, os.path.join(_utf8(path), name))
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