#8295 : Added shutil.unpack_archive and related APIs

Lib/shutil.py

@@ -11,6 +11,7 @@
 import fnmatch
 import collections
 import errno
+import tarfile
 
 try:
     from pwd import getpwnam
@@ -25,7 +26,9 @@
 __all__ = ["copyfileobj", "copyfile", "copymode", "copystat", "copy", "copy2",
            "copytree", "move", "rmtree", "Error", "SpecialFileError",
            "ExecError", "make_archive", "get_archive_formats",
-           "register_archive_format", "unregister_archive_format"]
+           "register_archive_format", "unregister_archive_format",
+           "get_unpack_formats", "register_unpack_format",
+           "unregister_unpack_format", "unpack_archive"]
 
 class Error(EnvironmentError):
     pass
@@ -37,6 +40,14 @@ class SpecialFileError(EnvironmentError):
 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 registery operation with the archiving
+    and unpacking registeries fails"""
+
+
 try:
     WindowsError
 except NameError:
@@ -381,10 +392,7 @@ def _make_tarball(base_name, base_dir, compress="gzip", verbose=0, dry_run=0,
         if not dry_run:
             os.makedirs(archive_dir)
 
-
     # creating the tarball
-    import tarfile  # late import so Python build itself doesn't break
-
     if logger is not None:
         logger.info('Creating tar archive')
 
@@ -567,3 +575,165 @@ def make_archive(base_name, format, root_dir=None, base_dir=None, verbose=0,
             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, collections.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 registery."""
+    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"),
+    'bztar': (['.bz2'], _unpack_tarfile, [], "bzip2'ed tar-file"),
+    'tar':   (['.tar'], _unpack_tarfile, [], "uncompressed tar file"),
+    'zip':   (['.zip'], _unpack_zipfile, [], "ZIP 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[0]
+        func(filename, extract_dir, **dict(format_info[1]))
+    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)