Mini Shell

"""Utilities for extracting common archive formats"""

import zipfile
import tarfile
import os
import shutil
import posixpath
import contextlib
from distutils.errors import DistutilsError

from pkg_resources import ensure_directory

__all__ = [
    "unpack_archive", "unpack_zipfile", "unpack_tarfile", "default_filter",
    "UnrecognizedFormat", "extraction_drivers", "unpack_directory",
]


class UnrecognizedFormat(DistutilsError):
    """Couldn't recognize the archive type"""


def default_filter(src, dst):
    """The default progress/filter callback; returns True for all files"""
    return dst


def unpack_archive(
        filename, extract_dir, progress_filter=default_filter,
        drivers=None):
    """Unpack `filename` to `extract_dir`, or raise ``UnrecognizedFormat``

    `progress_filter` is a function taking two arguments: a source path
    internal to the archive ('/'-separated), and a filesystem path where it
    will be extracted.  The callback must return the desired extract path
    (which may be the same as the one passed in), or else ``None`` to skip
    that file or directory.  The callback can thus be used to report on the
    progress of the extraction, as well as to filter the items extracted or
    alter their extraction paths.

    `drivers`, if supplied, must be a non-empty sequence of functions with the
    same signature as this function (minus the `drivers` argument), that raise
    ``UnrecognizedFormat`` if they do not support extracting the designated
    archive type.  The `drivers` are tried in sequence until one is found that
    does not raise an error, or until all are exhausted (in which case
    ``UnrecognizedFormat`` is raised).  If you do not supply a sequence of
    drivers, the module's ``extraction_drivers`` constant will be used, which
    means that ``unpack_zipfile`` and ``unpack_tarfile`` will be tried, in that
    order.
    """
    for driver in drivers or extraction_drivers:
        try:
            driver(filename, extract_dir, progress_filter)
        except UnrecognizedFormat:
            continue
        else:
            return
    else:
        raise UnrecognizedFormat(
            "Not a recognized archive type: %s" % filename
        )


def unpack_directory(filename, extract_dir, progress_filter=default_filter):
    """"Unpack" a directory, using the same interface as for archives

    Raises ``UnrecognizedFormat`` if `filename` is not a directory
    """
    if not os.path.isdir(filename):
        raise UnrecognizedFormat("%s is not a directory" % filename)

    paths = {
        filename: ('', extract_dir),
    }
    for base, dirs, files in os.walk(filename):
        src, dst = paths[base]
        for d in dirs:
            paths[os.path.join(base, d)] = src + d + '/', os.path.join(dst, d)
        for f in files:
            target = os.path.join(dst, f)
            target = progress_filter(src + f, target)
            if not target:
                # skip non-files
                continue
            ensure_directory(target)
            f = os.path.join(base, f)
            shutil.copyfile(f, target)
            shutil.copystat(f, target)


def unpack_zipfile(filename, extract_dir, progress_filter=default_filter):
    """Unpack zip `filename` to `extract_dir`

    Raises ``UnrecognizedFormat`` if `filename` is not a zipfile (as determined
    by ``zipfile.is_zipfile()``).  See ``unpack_archive()`` for an explanation
    of the `progress_filter` argument.
    """

    if not zipfile.is_zipfile(filename):
        raise UnrecognizedFormat("%s is not a zip file" % (filename,))

    with zipfile.ZipFile(filename) as z:
        for info in z.infolist():
            name = info.filename

            # don't extract absolute paths or ones with .. in them
            if name.startswith('/') or '..' in name.split('/'):
                continue

            target = os.path.join(extract_dir, *name.split('/'))
            target = progress_filter(name, target)
            if not target:
                continue
            if name.endswith('/'):
                # directory
                ensure_directory(target)
            else:
                # file
                ensure_directory(target)
                data = z.read(info.filename)
                with open(target, 'wb') as f:
                    f.write(data)
            unix_attributes = info.external_attr >> 16
            if unix_attributes:
                os.chmod(target, unix_attributes)


def _resolve_tar_file_or_dir(tar_obj, tar_member_obj):
    """Resolve any links and extract link targets as normal files."""
    while tar_member_obj is not None and (
            tar_member_obj.islnk() or tar_member_obj.issym()):
        linkpath = tar_member_obj.linkname
        if tar_member_obj.issym():
            base = posixpath.dirname(tar_member_obj.name)
            linkpath = posixpath.join(base, linkpath)
            linkpath = posixpath.normpath(linkpath)
        tar_member_obj = tar_obj._getmember(linkpath)

    is_file_or_dir = (
        tar_member_obj is not None and
        (tar_member_obj.isfile() or tar_member_obj.isdir())
    )
    if is_file_or_dir:
        return tar_member_obj

    raise LookupError('Got unknown file type')


def _iter_open_tar(tar_obj, extract_dir, progress_filter):
    """Emit member-destination pairs from a tar archive."""
    # don't do any chowning!
    tar_obj.chown = lambda *args: None

    with contextlib.closing(tar_obj):
        for member in tar_obj:
            name = member.name
            # don't extract absolute paths or ones with .. in them
            if name.startswith('/') or '..' in name.split('/'):
                continue

            prelim_dst = os.path.join(extract_dir, *name.split('/'))

            try:
                member = _resolve_tar_file_or_dir(tar_obj, member)
            except LookupError:
                continue

            final_dst = progress_filter(name, prelim_dst)
            if not final_dst:
                continue

            if final_dst.endswith(os.sep):
                final_dst = final_dst[:-1]

            yield member, final_dst


def unpack_tarfile(filename, extract_dir, progress_filter=default_filter):
    """Unpack tar/tar.gz/tar.bz2 `filename` to `extract_dir`

    Raises ``UnrecognizedFormat`` if `filename` is not a tarfile (as determined
    by ``tarfile.open()``).  See ``unpack_archive()`` for an explanation
    of the `progress_filter` argument.
    """
    try:
        tarobj = tarfile.open(filename)
    except tarfile.TarError as e:
        raise UnrecognizedFormat(
            "%s is not a compressed or uncompressed tar file" % (filename,)
        ) from e

    for member, final_dst in _iter_open_tar(
            tarobj, extract_dir, progress_filter,
    ):
        try:
            # XXX Ugh
            tarobj._extract_member(member, final_dst)
        except tarfile.ExtractError:
            # chown/chmod/mkfifo/mknode/makedev failed
            pass

    return True


extraction_drivers = unpack_directory, unpack_zipfile, unpack_tarfile