diff env/lib/python3.9/site-packages/distlib/_backport/shutil.py @ 0:4f3585e2f14b draft default tip

"planemo upload commit 60cee0fc7c0cda8592644e1aad72851dec82c959"

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/env/lib/python3.9/site-packages/distlib/_backport/shutil.py	Mon Mar 22 18:12:50 2021 +0000
@@ -0,0 +1,764 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright (C) 2012 The Python Software Foundation.
+# See LICENSE.txt and CONTRIBUTORS.txt.
+#
+"""Utility functions for copying and archiving files and directory trees.
+
+XXX The functions here don't copy the resource fork or other metadata on Mac.
+
+"""
+
+import os
+import sys
+import stat
+from os.path import abspath
+import fnmatch
+try:
+    from collections.abc import Callable
+except ImportError:
+    from collections import Callable
+import errno
+from . import tarfile
+
+try:
+    import bz2
+    _BZ2_SUPPORTED = True
+except ImportError:
+    _BZ2_SUPPORTED = False
+
+try:
+    from pwd import getpwnam
+except ImportError:
+    getpwnam = None
+
+try:
+    from grp import getgrnam
+except ImportError:
+    getgrnam = None
+
+__all__ = ["copyfileobj", "copyfile", "copymode", "copystat", "copy", "copy2",
+           "copytree", "move", "rmtree", "Error", "SpecialFileError",
+           "ExecError", "make_archive", "get_archive_formats",
+           "register_archive_format", "unregister_archive_format",
+           "get_unpack_formats", "register_unpack_format",
+           "unregister_unpack_format", "unpack_archive", "ignore_patterns"]
+
+class Error(EnvironmentError):
+    pass
+
+class SpecialFileError(EnvironmentError):
+    """Raised when trying to do a kind of operation (e.g. copying) which is
+    not supported on a special file (e.g. a named pipe)"""
+
+class ExecError(EnvironmentError):
+    """Raised when a command could not be executed"""
+
+class ReadError(EnvironmentError):
+    """Raised when an archive cannot be read"""
+
+class RegistryError(Exception):
+    """Raised when a registry operation with the archiving
+    and unpacking registries fails"""
+
+
+try:
+    WindowsError
+except NameError:
+    WindowsError = None
+
+def copyfileobj(fsrc, fdst, length=16*1024):
+    """copy data from file-like object fsrc to file-like object fdst"""
+    while 1:
+        buf = fsrc.read(length)
+        if not buf:
+            break
+        fdst.write(buf)
+
+def _samefile(src, dst):
+    # Macintosh, Unix.
+    if hasattr(os.path, 'samefile'):
+        try:
+            return os.path.samefile(src, dst)
+        except OSError:
+            return False
+
+    # All other platforms: check for same pathname.
+    return (os.path.normcase(os.path.abspath(src)) ==
+            os.path.normcase(os.path.abspath(dst)))
+
+def copyfile(src, dst):
+    """Copy data from src to dst"""
+    if _samefile(src, dst):
+        raise Error("`%s` and `%s` are the same file" % (src, dst))
+
+    for fn in [src, dst]:
+        try:
+            st = os.stat(fn)
+        except OSError:
+            # File most likely does not exist
+            pass
+        else:
+            # XXX What about other special files? (sockets, devices...)
+            if stat.S_ISFIFO(st.st_mode):
+                raise SpecialFileError("`%s` is a named pipe" % fn)
+
+    with open(src, 'rb') as fsrc:
+        with open(dst, 'wb') as fdst:
+            copyfileobj(fsrc, fdst)
+
+def copymode(src, dst):
+    """Copy mode bits from src to dst"""
+    if hasattr(os, 'chmod'):
+        st = os.stat(src)
+        mode = stat.S_IMODE(st.st_mode)
+        os.chmod(dst, mode)
+
+def copystat(src, dst):
+    """Copy all stat info (mode bits, atime, mtime, flags) from src to dst"""
+    st = os.stat(src)
+    mode = stat.S_IMODE(st.st_mode)
+    if hasattr(os, 'utime'):
+        os.utime(dst, (st.st_atime, st.st_mtime))
+    if hasattr(os, 'chmod'):
+        os.chmod(dst, mode)
+    if hasattr(os, 'chflags') and hasattr(st, 'st_flags'):
+        try:
+            os.chflags(dst, st.st_flags)
+        except OSError as why:
+            if (not hasattr(errno, 'EOPNOTSUPP') or
+                why.errno != errno.EOPNOTSUPP):
+                raise
+
+def copy(src, dst):
+    """Copy data and mode bits ("cp src dst").
+
+    The destination may be a directory.
+
+    """
+    if os.path.isdir(dst):
+        dst = os.path.join(dst, os.path.basename(src))
+    copyfile(src, dst)
+    copymode(src, dst)
+
+def copy2(src, dst):
+    """Copy data and all stat info ("cp -p src dst").
+
+    The destination may be a directory.
+
+    """
+    if os.path.isdir(dst):
+        dst = os.path.join(dst, os.path.basename(src))
+    copyfile(src, dst)
+    copystat(src, dst)
+
+def ignore_patterns(*patterns):
+    """Function that can be used as copytree() ignore parameter.
+
+    Patterns is a sequence of glob-style patterns
+    that are used to exclude files"""
+    def _ignore_patterns(path, names):
+        ignored_names = []
+        for pattern in patterns:
+            ignored_names.extend(fnmatch.filter(names, pattern))
+        return set(ignored_names)
+    return _ignore_patterns
+
+def copytree(src, dst, symlinks=False, ignore=None, copy_function=copy2,
+             ignore_dangling_symlinks=False):
+    """Recursively copy a directory tree.
+
+    The destination directory must not already exist.
+    If exception(s) occur, an Error is raised with a list of reasons.
+
+    If the optional symlinks flag is true, symbolic links in the
+    source tree result in symbolic links in the destination tree; if
+    it is false, the contents of the files pointed to by symbolic
+    links are copied. If the file pointed by the symlink doesn't
+    exist, an exception will be added in the list of errors raised in
+    an Error exception at the end of the copy process.
+
+    You can set the optional ignore_dangling_symlinks flag to true if you
+    want to silence this exception. Notice that this has no effect on
+    platforms that don't support os.symlink.
+
+    The optional ignore argument is a callable. If given, it
+    is called with the `src` parameter, which is the directory
+    being visited by copytree(), and `names` which is the list of
+    `src` contents, as returned by os.listdir():
+
+        callable(src, names) -> ignored_names
+
+    Since copytree() is called recursively, the callable will be
+    called once for each directory that is copied. It returns a
+    list of names relative to the `src` directory that should
+    not be copied.
+
+    The optional copy_function argument is a callable that will be used
+    to copy each file. It will be called with the source path and the
+    destination path as arguments. By default, copy2() is used, but any
+    function that supports the same signature (like copy()) can be used.
+
+    """
+    names = os.listdir(src)
+    if ignore is not None:
+        ignored_names = ignore(src, names)
+    else:
+        ignored_names = set()
+
+    os.makedirs(dst)
+    errors = []
+    for name in names:
+        if name in ignored_names:
+            continue
+        srcname = os.path.join(src, name)
+        dstname = os.path.join(dst, name)
+        try:
+            if os.path.islink(srcname):
+                linkto = os.readlink(srcname)
+                if symlinks:
+                    os.symlink(linkto, dstname)
+                else:
+                    # ignore dangling symlink if the flag is on
+                    if not os.path.exists(linkto) and ignore_dangling_symlinks:
+                        continue
+                    # otherwise let the copy occurs. copy2 will raise an error
+                    copy_function(srcname, dstname)
+            elif os.path.isdir(srcname):
+                copytree(srcname, dstname, symlinks, ignore, copy_function)
+            else:
+                # Will raise a SpecialFileError for unsupported file types
+                copy_function(srcname, dstname)
+        # catch the Error from the recursive copytree so that we can
+        # continue with other files
+        except Error as err:
+            errors.extend(err.args[0])
+        except EnvironmentError as why:
+            errors.append((srcname, dstname, str(why)))
+    try:
+        copystat(src, dst)
+    except OSError as why:
+        if WindowsError is not None and isinstance(why, WindowsError):
+            # Copying file access times may fail on Windows
+            pass
+        else:
+            errors.extend((src, dst, str(why)))
+    if errors:
+        raise Error(errors)
+
+def rmtree(path, ignore_errors=False, onerror=None):
+    """Recursively delete a directory tree.
+
+    If ignore_errors is set, errors are ignored; otherwise, if onerror
+    is set, it is called to handle the error with arguments (func,
+    path, exc_info) where func is os.listdir, os.remove, or os.rmdir;
+    path is the argument to that function that caused it to fail; and
+    exc_info is a tuple returned by sys.exc_info().  If ignore_errors
+    is false and onerror is None, an exception is raised.
+
+    """
+    if ignore_errors:
+        def onerror(*args):
+            pass
+    elif onerror is None:
+        def onerror(*args):
+            raise
+    try:
+        if os.path.islink(path):
+            # symlinks to directories are forbidden, see bug #1669
+            raise OSError("Cannot call rmtree on a symbolic link")
+    except OSError:
+        onerror(os.path.islink, path, sys.exc_info())
+        # can't continue even if onerror hook returns
+        return
+    names = []
+    try:
+        names = os.listdir(path)
+    except os.error:
+        onerror(os.listdir, path, sys.exc_info())
+    for name in names:
+        fullname = os.path.join(path, name)
+        try:
+            mode = os.lstat(fullname).st_mode
+        except os.error:
+            mode = 0
+        if stat.S_ISDIR(mode):
+            rmtree(fullname, ignore_errors, onerror)
+        else:
+            try:
+                os.remove(fullname)
+            except os.error:
+                onerror(os.remove, fullname, sys.exc_info())
+    try:
+        os.rmdir(path)
+    except os.error:
+        onerror(os.rmdir, path, sys.exc_info())
+
+
+def _basename(path):
+    # A basename() variant which first strips the trailing slash, if present.
+    # Thus we always get the last component of the path, even for directories.
+    return os.path.basename(path.rstrip(os.path.sep))
+
+def move(src, dst):
+    """Recursively move a file or directory to another location. This is
+    similar to the Unix "mv" command.
+
+    If the destination is a directory or a symlink to a directory, the source
+    is moved inside the directory. The destination path must not already
+    exist.
+
+    If the destination already exists but is not a directory, it may be
+    overwritten depending on os.rename() semantics.
+
+    If the destination is on our current filesystem, then rename() is used.
+    Otherwise, src is copied to the destination and then removed.
+    A lot more could be done here...  A look at a mv.c shows a lot of
+    the issues this implementation glosses over.
+
+    """
+    real_dst = dst
+    if os.path.isdir(dst):
+        if _samefile(src, dst):
+            # We might be on a case insensitive filesystem,
+            # perform the rename anyway.
+            os.rename(src, dst)
+            return
+
+        real_dst = os.path.join(dst, _basename(src))
+        if os.path.exists(real_dst):
+            raise Error("Destination path '%s' already exists" % real_dst)
+    try:
+        os.rename(src, real_dst)
+    except OSError:
+        if os.path.isdir(src):
+            if _destinsrc(src, dst):
+                raise Error("Cannot move a directory '%s' into itself '%s'." % (src, dst))
+            copytree(src, real_dst, symlinks=True)
+            rmtree(src)
+        else:
+            copy2(src, real_dst)
+            os.unlink(src)
+
+def _destinsrc(src, dst):
+    src = abspath(src)
+    dst = abspath(dst)
+    if not src.endswith(os.path.sep):
+        src += os.path.sep
+    if not dst.endswith(os.path.sep):
+        dst += os.path.sep
+    return dst.startswith(src)
+
+def _get_gid(name):
+    """Returns a gid, given a group name."""
+    if getgrnam is None or name is None:
+        return None
+    try:
+        result = getgrnam(name)
+    except KeyError:
+        result = None
+    if result is not None:
+        return result[2]
+    return None
+
+def _get_uid(name):
+    """Returns an uid, given a user name."""
+    if getpwnam is None or name is None:
+        return None
+    try:
+        result = getpwnam(name)
+    except KeyError:
+        result = None
+    if result is not None:
+        return result[2]
+    return None
+
+def _make_tarball(base_name, base_dir, compress="gzip", verbose=0, dry_run=0,
+                  owner=None, group=None, logger=None):
+    """Create a (possibly compressed) tar file from all the files under
+    'base_dir'.
+
+    'compress' must be "gzip" (the default), "bzip2", or None.
+
+    'owner' and 'group' can be used to define an owner and a group for the
+    archive that is being built. If not provided, the current owner and group
+    will be used.
+
+    The output tar file will be named 'base_name' +  ".tar", possibly plus
+    the appropriate compression extension (".gz", or ".bz2").
+
+    Returns the output filename.
+    """
+    tar_compression = {'gzip': 'gz', None: ''}
+    compress_ext = {'gzip': '.gz'}
+
+    if _BZ2_SUPPORTED:
+        tar_compression['bzip2'] = 'bz2'
+        compress_ext['bzip2'] = '.bz2'
+
+    # flags for compression program, each element of list will be an argument
+    if compress is not None and compress not in compress_ext:
+        raise ValueError("bad value for 'compress', or compression format not "
+                         "supported : {0}".format(compress))
+
+    archive_name = base_name + '.tar' + compress_ext.get(compress, '')
+    archive_dir = os.path.dirname(archive_name)
+
+    if not os.path.exists(archive_dir):
+        if logger is not None:
+            logger.info("creating %s", archive_dir)
+        if not dry_run:
+            os.makedirs(archive_dir)
+
+    # creating the tarball
+    if logger is not None:
+        logger.info('Creating tar archive')
+
+    uid = _get_uid(owner)
+    gid = _get_gid(group)
+
+    def _set_uid_gid(tarinfo):
+        if gid is not None:
+            tarinfo.gid = gid
+            tarinfo.gname = group
+        if uid is not None:
+            tarinfo.uid = uid
+            tarinfo.uname = owner
+        return tarinfo
+
+    if not dry_run:
+        tar = tarfile.open(archive_name, 'w|%s' % tar_compression[compress])
+        try:
+            tar.add(base_dir, filter=_set_uid_gid)
+        finally:
+            tar.close()
+
+    return archive_name
+
+def _call_external_zip(base_dir, zip_filename, verbose=False, dry_run=False):
+    # XXX see if we want to keep an external call here
+    if verbose:
+        zipoptions = "-r"
+    else:
+        zipoptions = "-rq"
+    from distutils.errors import DistutilsExecError
+    from distutils.spawn import spawn
+    try:
+        spawn(["zip", zipoptions, zip_filename, base_dir], dry_run=dry_run)
+    except DistutilsExecError:
+        # XXX really should distinguish between "couldn't find
+        # external 'zip' command" and "zip failed".
+        raise ExecError("unable to create zip file '%s': "
+            "could neither import the 'zipfile' module nor "
+            "find a standalone zip utility") % zip_filename
+
+def _make_zipfile(base_name, base_dir, verbose=0, dry_run=0, logger=None):
+    """Create a zip file from all the files under 'base_dir'.
+
+    The output zip file will be named 'base_name' + ".zip".  Uses either the
+    "zipfile" Python module (if available) or the InfoZIP "zip" utility
+    (if installed and found on the default search path).  If neither tool is
+    available, raises ExecError.  Returns the name of the output zip
+    file.
+    """
+    zip_filename = base_name + ".zip"
+    archive_dir = os.path.dirname(base_name)
+
+    if not os.path.exists(archive_dir):
+        if logger is not None:
+            logger.info("creating %s", archive_dir)
+        if not dry_run:
+            os.makedirs(archive_dir)
+
+    # If zipfile module is not available, try spawning an external 'zip'
+    # command.
+    try:
+        import zipfile
+    except ImportError:
+        zipfile = None
+
+    if zipfile is None:
+        _call_external_zip(base_dir, zip_filename, verbose, dry_run)
+    else:
+        if logger is not None:
+            logger.info("creating '%s' and adding '%s' to it",
+                        zip_filename, base_dir)
+
+        if not dry_run:
+            zip = zipfile.ZipFile(zip_filename, "w",
+                                  compression=zipfile.ZIP_DEFLATED)
+
+            for dirpath, dirnames, filenames in os.walk(base_dir):
+                for name in filenames:
+                    path = os.path.normpath(os.path.join(dirpath, name))
+                    if os.path.isfile(path):
+                        zip.write(path, path)
+                        if logger is not None:
+                            logger.info("adding '%s'", path)
+            zip.close()
+
+    return zip_filename
+
+_ARCHIVE_FORMATS = {
+    'gztar': (_make_tarball, [('compress', 'gzip')], "gzip'ed tar-file"),
+    'bztar': (_make_tarball, [('compress', 'bzip2')], "bzip2'ed tar-file"),
+    'tar':   (_make_tarball, [('compress', None)], "uncompressed tar file"),
+    'zip':   (_make_zipfile, [], "ZIP file"),
+    }
+
+if _BZ2_SUPPORTED:
+    _ARCHIVE_FORMATS['bztar'] = (_make_tarball, [('compress', 'bzip2')],
+                                "bzip2'ed tar-file")
+
+def get_archive_formats():
+    """Returns a list of supported formats for archiving and unarchiving.
+
+    Each element of the returned sequence is a tuple (name, description)
+    """
+    formats = [(name, registry[2]) for name, registry in
+               _ARCHIVE_FORMATS.items()]
+    formats.sort()
+    return formats
+
+def register_archive_format(name, function, extra_args=None, description=''):
+    """Registers an archive format.
+
+    name is the name of the format. function is the callable that will be
+    used to create archives. If provided, extra_args is a sequence of
+    (name, value) tuples that will be passed as arguments to the callable.
+    description can be provided to describe the format, and will be returned
+    by the get_archive_formats() function.
+    """
+    if extra_args is None:
+        extra_args = []
+    if not isinstance(function, Callable):
+        raise TypeError('The %s object is not callable' % function)
+    if not isinstance(extra_args, (tuple, list)):
+        raise TypeError('extra_args needs to be a sequence')
+    for element in extra_args:
+        if not isinstance(element, (tuple, list)) or len(element) !=2:
+            raise TypeError('extra_args elements are : (arg_name, value)')
+
+    _ARCHIVE_FORMATS[name] = (function, extra_args, description)
+
+def unregister_archive_format(name):
+    del _ARCHIVE_FORMATS[name]
+
+def make_archive(base_name, format, root_dir=None, base_dir=None, verbose=0,
+                 dry_run=0, owner=None, group=None, logger=None):
+    """Create an archive file (eg. zip or tar).
+
+    'base_name' is the name of the file to create, minus any format-specific
+    extension; 'format' is the archive format: one of "zip", "tar", "bztar"
+    or "gztar".
+
+    'root_dir' is a directory that will be the root directory of the
+    archive; ie. we typically chdir into 'root_dir' before creating the
+    archive.  'base_dir' is the directory where we start archiving from;
+    ie. 'base_dir' will be the common prefix of all files and
+    directories in the archive.  'root_dir' and 'base_dir' both default
+    to the current directory.  Returns the name of the archive file.
+
+    'owner' and 'group' are used when creating a tar archive. By default,
+    uses the current owner and group.
+    """
+    save_cwd = os.getcwd()
+    if root_dir is not None:
+        if logger is not None:
+            logger.debug("changing into '%s'", root_dir)
+        base_name = os.path.abspath(base_name)
+        if not dry_run:
+            os.chdir(root_dir)
+
+    if base_dir is None:
+        base_dir = os.curdir
+
+    kwargs = {'dry_run': dry_run, 'logger': logger}
+
+    try:
+        format_info = _ARCHIVE_FORMATS[format]
+    except KeyError:
+        raise ValueError("unknown archive format '%s'" % format)
+
+    func = format_info[0]
+    for arg, val in format_info[1]:
+        kwargs[arg] = val
+
+    if format != 'zip':
+        kwargs['owner'] = owner
+        kwargs['group'] = group
+
+    try:
+        filename = func(base_name, base_dir, **kwargs)
+    finally:
+        if root_dir is not None:
+            if logger is not None:
+                logger.debug("changing back to '%s'", save_cwd)
+            os.chdir(save_cwd)
+
+    return filename
+
+
+def get_unpack_formats():
+    """Returns a list of supported formats for unpacking.
+
+    Each element of the returned sequence is a tuple
+    (name, extensions, description)
+    """
+    formats = [(name, info[0], info[3]) for name, info in
+               _UNPACK_FORMATS.items()]
+    formats.sort()
+    return formats
+
+def _check_unpack_options(extensions, function, extra_args):
+    """Checks what gets registered as an unpacker."""
+    # first make sure no other unpacker is registered for this extension
+    existing_extensions = {}
+    for name, info in _UNPACK_FORMATS.items():
+        for ext in info[0]:
+            existing_extensions[ext] = name
+
+    for extension in extensions:
+        if extension in existing_extensions:
+            msg = '%s is already registered for "%s"'
+            raise RegistryError(msg % (extension,
+                                       existing_extensions[extension]))
+
+    if not isinstance(function, Callable):
+        raise TypeError('The registered function must be a callable')
+
+
+def register_unpack_format(name, extensions, function, extra_args=None,
+                           description=''):
+    """Registers an unpack format.
+
+    `name` is the name of the format. `extensions` is a list of extensions
+    corresponding to the format.
+
+    `function` is the callable that will be
+    used to unpack archives. The callable will receive archives to unpack.
+    If it's unable to handle an archive, it needs to raise a ReadError
+    exception.
+
+    If provided, `extra_args` is a sequence of
+    (name, value) tuples that will be passed as arguments to the callable.
+    description can be provided to describe the format, and will be returned
+    by the get_unpack_formats() function.
+    """
+    if extra_args is None:
+        extra_args = []
+    _check_unpack_options(extensions, function, extra_args)
+    _UNPACK_FORMATS[name] = extensions, function, extra_args, description
+
+def unregister_unpack_format(name):
+    """Removes the pack format from the registry."""
+    del _UNPACK_FORMATS[name]
+
+def _ensure_directory(path):
+    """Ensure that the parent directory of `path` exists"""
+    dirname = os.path.dirname(path)
+    if not os.path.isdir(dirname):
+        os.makedirs(dirname)
+
+def _unpack_zipfile(filename, extract_dir):
+    """Unpack zip `filename` to `extract_dir`
+    """
+    try:
+        import zipfile
+    except ImportError:
+        raise ReadError('zlib not supported, cannot unpack this archive.')
+
+    if not zipfile.is_zipfile(filename):
+        raise ReadError("%s is not a zip file" % filename)
+
+    zip = zipfile.ZipFile(filename)
+    try:
+        for info in zip.infolist():
+            name = info.filename
+
+            # don't extract absolute paths or ones with .. in them
+            if name.startswith('/') or '..' in name:
+                continue
+
+            target = os.path.join(extract_dir, *name.split('/'))
+            if not target:
+                continue
+
+            _ensure_directory(target)
+            if not name.endswith('/'):
+                # file
+                data = zip.read(info.filename)
+                f = open(target, 'wb')
+                try:
+                    f.write(data)
+                finally:
+                    f.close()
+                    del data
+    finally:
+        zip.close()
+
+def _unpack_tarfile(filename, extract_dir):
+    """Unpack tar/tar.gz/tar.bz2 `filename` to `extract_dir`
+    """
+    try:
+        tarobj = tarfile.open(filename)
+    except tarfile.TarError:
+        raise ReadError(
+            "%s is not a compressed or uncompressed tar file" % filename)
+    try:
+        tarobj.extractall(extract_dir)
+    finally:
+        tarobj.close()
+
+_UNPACK_FORMATS = {
+    'gztar': (['.tar.gz', '.tgz'], _unpack_tarfile, [], "gzip'ed tar-file"),
+    'tar':   (['.tar'], _unpack_tarfile, [], "uncompressed tar file"),
+    'zip':   (['.zip'], _unpack_zipfile, [], "ZIP file")
+    }
+
+if _BZ2_SUPPORTED:
+    _UNPACK_FORMATS['bztar'] = (['.bz2'], _unpack_tarfile, [],
+                                "bzip2'ed tar-file")
+
+def _find_unpack_format(filename):
+    for name, info in _UNPACK_FORMATS.items():
+        for extension in info[0]:
+            if filename.endswith(extension):
+                return name
+    return None
+
+def unpack_archive(filename, extract_dir=None, format=None):
+    """Unpack an archive.
+
+    `filename` is the name of the archive.
+
+    `extract_dir` is the name of the target directory, where the archive
+    is unpacked. If not provided, the current working directory is used.
+
+    `format` is the archive format: one of "zip", "tar", or "gztar". Or any
+    other registered format. If not provided, unpack_archive will use the
+    filename extension and see if an unpacker was registered for that
+    extension.
+
+    In case none is found, a ValueError is raised.
+    """
+    if extract_dir is None:
+        extract_dir = os.getcwd()
+
+    if format is not None:
+        try:
+            format_info = _UNPACK_FORMATS[format]
+        except KeyError:
+            raise ValueError("Unknown unpack format '{0}'".format(format))
+
+        func = format_info[1]
+        func(filename, extract_dir, **dict(format_info[2]))
+    else:
+        # we need to look at the registered unpackers supported extensions
+        format = _find_unpack_format(filename)
+        if format is None:
+            raise ReadError("Unknown archive format '{0}'".format(filename))
+
+        func = _UNPACK_FORMATS[format][1]
+        kwargs = dict(_UNPACK_FORMATS[format][2])
+        func(filename, extract_dir, **kwargs)