# -*- coding: utf-8 -*-
"""The file object file input/output (IO) object implementation."""
import abc
import os
from dfvfs.file_io import file_io
[docs]
class FileObjectIO(file_io.FileIO):
"""Base class for file object-based file input/output (IO) object."""
# pylint: disable=redundant-returns-doc
[docs]
def __init__(self, resolver_context, path_spec):
"""Initializes a file input/output (IO) object.
Args:
resolver_context (Context): resolver context.
path_spec (PathSpec): a path specification.
"""
super(FileObjectIO, self).__init__(resolver_context, path_spec)
self._file_object = None
self._size = None
def _Close(self):
"""Closes the file-like object."""
self._file_object.close()
self._file_object = None
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.
"""
self._file_object = self._OpenFileObject(self._path_spec)
if not self._file_object:
raise IOError('Unable to open missing file-like object.')
# pylint: disable=redundant-returns-doc
@abc.abstractmethod
def _OpenFileObject(self, path_spec):
"""Opens the file-like object defined by path specification.
Args:
path_spec (PathSpec): path specification.
Returns:
FileIO: a file-like object.
Raises:
PathSpecError: if the path specification is incorrect.
"""
# 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.')
# Do not pass the size argument as a keyword argument since it breaks
# some file-like object implementations.
return self._file_object.read(size)
[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.')
self._file_object.seek(offset, whence)
[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.')
if not hasattr(self._file_object, 'get_offset'):
return self._file_object.tell()
return self._file_object.get_offset()
[docs]
def get_size(self):
"""Retrieves the size of the file-like object.
Returns:
int: size of the file-like object 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.')
if not hasattr(self._file_object, 'get_size'):
if not self._size:
current_offset = self.get_offset()
self.seek(0, os.SEEK_END)
self._size = self.get_offset()
self.seek(current_offset, os.SEEK_SET)
return self._size
return self._file_object.get_size()