# -*- coding: utf-8 -*-
"""The Volume Shadow Snapshots (VSS) file system implementation."""
import pyvshadow
from dfvfs.lib import definitions
from dfvfs.lib import errors
from dfvfs.lib import vshadow_helper
from dfvfs.path import vshadow_path_spec
from dfvfs.resolver import resolver
from dfvfs.vfs import file_system
from dfvfs.vfs import vshadow_file_entry
[docs]
class VShadowFileSystem(file_system.FileSystem):
"""File system that uses pyvshadow."""
TYPE_INDICATOR = definitions.TYPE_INDICATOR_VSHADOW
[docs]
def __init__(self, resolver_context, path_spec):
"""Initializes a file system.
Args:
resolver_context (Context): resolver context.
path_spec (PathSpec): a path specification.
"""
super(VShadowFileSystem, self).__init__(resolver_context, path_spec)
self._file_object = None
self._vshadow_volume = None
def _Close(self):
"""Closes the file system.
Raises:
IOError: if the close failed.
"""
self._vshadow_volume.close()
self._vshadow_volume = None
self._file_object = None
def _Open(self, mode='rb'):
"""Opens the file system object defined by path specification.
Args:
mode (Optional[str]): file access mode. The default is 'rb' which
represents read-only binary.
Raises:
AccessError: if the access to open the file was denied.
IOError: if the file system object could not be opened.
PathSpecError: if the path specification is incorrect.
ValueError: if the path specification is invalid.
"""
if not self._path_spec.HasParent():
raise errors.PathSpecError(
'Unsupported path specification without parent.')
file_object = resolver.Resolver.OpenFileObject(
self._path_spec.parent, resolver_context=self._resolver_context)
vshadow_volume = pyvshadow.volume()
vshadow_volume.open_file_object(file_object)
self._file_object = file_object
self._vshadow_volume = vshadow_volume
[docs]
def FileEntryExistsByPathSpec(self, path_spec):
"""Determines if a file entry for a path specification exists.
Args:
path_spec (PathSpec): path specification.
Returns:
bool: True if the file entry exists.
"""
store_index = vshadow_helper.VShadowPathSpecGetStoreIndex(path_spec)
# The virtual root file has no corresponding store index but
# should have a location.
if store_index is None:
location = getattr(path_spec, 'location', None)
return location is not None and location == self.LOCATION_ROOT
return 0 <= store_index < self._vshadow_volume.number_of_stores
[docs]
def GetFileEntryByPathSpec(self, path_spec):
"""Retrieves a file entry for a path specification.
Args:
path_spec (PathSpec): path specification.
Returns:
VShadowFileEntry: file entry or None if not available.
"""
store_index = vshadow_helper.VShadowPathSpecGetStoreIndex(path_spec)
# The virtual root file has no corresponding store index but
# should have a location.
if store_index is None:
location = getattr(path_spec, 'location', None)
if location is None or location != self.LOCATION_ROOT:
return None
return vshadow_file_entry.VShadowFileEntry(
self._resolver_context, self, path_spec, is_root=True,
is_virtual=True)
if store_index < 0 or store_index >= self._vshadow_volume.number_of_stores:
return None
return vshadow_file_entry.VShadowFileEntry(
self._resolver_context, self, path_spec)
[docs]
def GetRootFileEntry(self):
"""Retrieves the root file entry.
Returns:
VShadowFileEntry: file entry or None if not available.
"""
path_spec = vshadow_path_spec.VShadowPathSpec(
location=self.LOCATION_ROOT, parent=self._path_spec.parent)
return self.GetFileEntryByPathSpec(path_spec)
[docs]
def GetVShadowStoreByPathSpec(self, path_spec):
"""Retrieves a VSS store for a path specification.
Args:
path_spec (PathSpec): path specification.
Returns:
pyvshadow.store: a VSS store or None if not available.
"""
store_index = vshadow_helper.VShadowPathSpecGetStoreIndex(path_spec)
if store_index is None:
return None
return self._vshadow_volume.get_store(store_index)
[docs]
def GetVShadowVolume(self):
"""Retrieves a VSS volume.
Returns:
pyvshadow.volume: a VSS volume.
"""
return self._vshadow_volume