# -*- coding: utf-8 -*-
"""The fake file-like object implementation."""
import os
from dfvfs.file_io import file_io
from dfvfs.lib import errors
[docs]
class FakeFile(file_io.FileIO):
"""Fake file input/output (IO) object."""
[docs]
def __init__(self, resolver_context, path_spec, file_data):
"""Initializes a file input/output (IO) object.
Args:
resolver_context (Context): resolver context.
path_spec (PathSpec): a path specification.
file_data (bytes): fake file data.
"""
super(FakeFile, self).__init__(resolver_context, path_spec)
self._current_offset = 0
self._file_data = file_data
self._size = 0
def _Close(self):
"""Closes the file-like object."""
return
def _Open(self, mode='rb'):
"""Opens the file-like object defined by path specification.
Args:
mode (Optional[str]): file access mode.
Raises:
AccessError: if the access to open the file was denied.
IOError: if the file-like object could not be opened.
OSError: if the file-like object could not be opened.
PathSpecError: if the path specification is incorrect.
"""
if self._path_spec.HasParent():
raise errors.PathSpecError('Unsupported path specification with parent.')
location = getattr(self._path_spec, 'location', None)
if location is None:
raise errors.PathSpecError('Path specification missing location.')
self._current_offset = 0
self._size = len(self._file_data)
# Note: that the following functions do not follow the style guide
# because they are part of the file-like object interface.
# pylint: disable=invalid-name
[docs]
def read(self, size=None):
"""Reads a byte string from the file-like object at the current offset.
The function will read a byte string of the specified size or
all of the remaining data if no size was specified.
Args:
size (Optional[int]): number of bytes to read, where None is all
remaining data.
Returns:
bytes: data read.
Raises:
IOError: if the read failed.
OSError: if the read failed.
"""
if not self._is_open:
raise IOError('Not opened.')
if self._current_offset < 0:
raise IOError((
f'Invalid current offset: {self._current_offset:d} value less than '
f'zero.'))
if self._file_data is None or self._current_offset >= self._size:
return b''
if size is None:
size = self._size
if self._current_offset + size > self._size:
size = self._size - self._current_offset
start_offset = self._current_offset
self._current_offset += size
return self._file_data[start_offset:self._current_offset]
[docs]
def seek(self, offset, whence=os.SEEK_SET):
"""Seeks to an offset within the file-like object.
Args:
offset (int): offset to seek to.
whence (Optional(int)): value that indicates whether offset is an absolute
or relative position within the file.
Raises:
IOError: if the seek failed.
OSError: if the seek failed.
"""
if not self._is_open:
raise IOError('Not opened.')
if whence == os.SEEK_CUR:
offset += self._current_offset
elif whence == os.SEEK_END:
offset += self._size
elif whence != os.SEEK_SET:
raise IOError('Unsupported whence.')
if offset < 0:
raise IOError('Invalid offset value less than zero.')
self._current_offset = offset
[docs]
def get_offset(self):
"""Retrieves the current offset into the file-like object.
Returns:
int: current offset into the file-like object.
Raises:
IOError: if the file-like object has not been opened.
OSError: if the file-like object has not been opened.
"""
if not self._is_open:
raise IOError('Not opened.')
return self._current_offset
[docs]
def get_size(self):
"""Retrieves the size of the file-like object.
Returns:
int: size of the file data.
Raises:
IOError: if the file-like object has not been opened.
OSError: if the file-like object has not been opened.
"""
if not self._is_open:
raise IOError('Not opened.')
return self._size