def _EntriesGenerator(self):
"""Retrieves directory entries.
Since a directory can contain a vast number of entries using
a generator is more memory efficient.
Yields:
A path specification (instance of path.OSPathSpec).
Raises:
AccessError: if the access to list the directory was denied.
BackEndError: if the directory could not be listed.
"""
location = getattr(self.path_spec, u'location', None)
if location is None:
return
# Windows will raise WindowsError, which can be caught by OSError,
# if the process has not access to list the directory. The os.access()
# function cannot be used since it will return true even when os.listdir()
# fails.
try:
for directory_entry in os.listdir(location):
directory_entry_location = self._file_system.JoinPath(
[location, directory_entry])
yield os_path_spec.OSPathSpec(
location=directory_entry_location)
except OSError as exception:
if exception.errno == errno.EACCES:
exception_string = str(exception)
if not isinstance(exception_string, py2to3.UNICODE_TYPE):
exception_string = py2to3.UNICODE_TYPE(exception_string,
errors=u'replace')
raise errors.AccessError(
u'Access to directory denied with error: {0:s}'.format(
exception_string))
else:
raise errors.BackEndError(
u'Unable to list directory: {0:s} with error: {1:s}'.
format(location, exception))
def FileEntryExistsByPathSpec(self, path_spec):
"""Determines if a file entry for a path specification exists.
Args:
path_spec: a path specification (instance of path.PathSpec).
Returns:
Boolean indicating if the file entry exists.
"""
location = getattr(path_spec, u'location', None)
if location is None:
return False
is_device = False
if platform.system() == u'Windows':
# Windows does not support running os.path.exists on device files
# so we use libsmdev to do the check.
try:
is_device = pysmdev.check_device(location)
except IOError as exception:
# Since pysmdev will raise IOError when it has no access to the device
# we check if the exception message contains ' access denied ' and
# return true.
# Note that exception.message no longer works in Python 3.
exception_string = str(exception)
if not isinstance(exception_string, py2to3.UNICODE_TYPE):
exception_string = py2to3.UNICODE_TYPE(exception_string,
errors=u'replace')
if u' access denied ' in exception_string:
is_device = True
if not is_device and not os.path.exists(location):
return False
return True
def FileEntryExistsByPathSpec(self, path_spec):
"""Determines if a file entry for a path specification exists.
Args:
path_spec (PathSpec): a path specification.
Returns:
bool: True if the file entry exists, false otherwise.
"""
location = getattr(path_spec, 'location', None)
if location is None:
return False
is_device = False
if platform.system() == 'Windows':
# Note that os.path.exists() returns False for Windows device files so
# instead use libsmdev to do the check.
try:
is_device = pysmdev.check_device(location)
except IOError as exception:
# Since pysmdev will raise IOError when it has no access to the device
# we check if the exception message contains ' access denied ' and
# return true.
# Note that exception.message no longer works in Python 3.
exception_string = str(exception)
if not isinstance(exception_string, py2to3.UNICODE_TYPE):
exception_string = py2to3.UNICODE_TYPE(
exception_string, errors='replace')
if ' access denied ' in exception_string:
is_device = True
# Note that os.path.exists() returns False for broken symbolic links hence
# an additional check using os.path.islink() is necessary.
return is_device or os.path.exists(location) or os.path.islink(location)
def _Open(self, path_spec=None, mode='rb'):
"""Opens the file-like object defined by path specification.
Args:
path_spec: optional path specification (instance of path.PathSpec).
The default is None.
mode: optional file access mode. The default is 'rb' read-only binary.
Raises:
AccessError: if the access to open the file was denied.
IOError: if the file-like object could not be opened.
PathSpecError: if the path specification is incorrect.
ValueError: if the path specification is invalid.
"""
if not path_spec:
raise ValueError(u'Missing path specfication.')
if path_spec.HasParent():
raise errors.PathSpecError(
u'Unsupported path specification with parent.')
location = getattr(path_spec, u'location', None)
if location is None:
raise errors.PathSpecError(u'Path specification missing location.')
# Windows does not support running os.stat on device files so we use
# libsmdev to do an initial check.
try:
is_device = pysmdev.check_device(location)
except IOError as exception:
# Since os.stat() will not recognize Windows device file names and
# will return '[Error 87] The parameter is incorrect' we check here
# if pysmdev exception message contains ' access denied ' and raise
# AccessError instead.
# Note that exception.message no longer works in Python 3.
exception_string = str(exception)
if not isinstance(exception_string, py2to3.UNICODE_TYPE):
exception_string = py2to3.UNICODE_TYPE(exception_string,
errors=u'replace')
if u' access denied ' in exception_string:
raise errors.AccessError(
u'Access denied to file: {0:s} with error: {1:s}'.format(
location, exception_string))
is_device = False
if not is_device:
try:
stat_info = os.stat(location)
except OSError as exception:
raise IOError(u'Unable to open file with error: {0:s}.'.format(
exception))
# In case the libsmdev check is not able to detect the device also use
# the stat information.
if stat.S_ISCHR(stat_info.st_mode) or stat.S_ISBLK(
stat_info.st_mode):
is_device = True
if is_device:
self._file_object = pysmdev.handle()
self._file_object.open(location, mode=mode)
self._size = self._file_object.media_size
else:
self._file_object = open(location, mode=mode)
self._size = stat_info.st_size
