# :coding: utf-8
# :copyright: Copyright (c) 2013 ftrack
from builtins import object
import os
from abc import ABCMeta, abstractmethod
import tempfile
from future.utils import with_metaclass
class Data(with_metaclass(ABCMeta, object)):
'''File-like object for manipulating data.'''
def __init__(self):
'''Initialise data access.'''
self.closed = False
@abstractmethod
def read(self, limit=None):
'''Return content from current position up to *limit*.'''
@abstractmethod
def write(self, content):
'''Write content at current position.'''
def flush(self):
'''Flush buffers ensuring data written.'''
def seek(self, offset, whence=os.SEEK_SET):
'''Move internal pointer by *offset*.
The *whence* argument is optional and defaults to os.SEEK_SET or 0
(absolute file positioning); other values are os.SEEK_CUR or 1
(seek relative to the current position) and os.SEEK_END or 2
(seek relative to the file's end).
'''
raise NotImplementedError('Seek not supported.')
def tell(self):
'''Return current position of internal pointer.'''
raise NotImplementedError('Tell not supported.')
def close(self):
'''Flush buffers and prevent further access.'''
self.flush()
self.closed = True
class FileWrapper(Data):
'''Data wrapper for Python file objects.'''
def __init__(self, wrapped_file):
'''Initialise access to *wrapped_file*.'''
self.wrapped_file = wrapped_file
self._read_since_last_write = False
super(FileWrapper, self).__init__()
def read(self, limit=None):
'''Return content from current position up to *limit*.'''
self._read_since_last_write = True
if limit is None:
limit = -1
return self.wrapped_file.read(limit)
def write(self, content):
'''Write content at current position.'''
if self._read_since_last_write:
# Windows requires a seek before switching from read to write.
self.seek(self.tell())
self.wrapped_file.write(content)
self._read_since_last_write = False
def flush(self):
'''Flush buffers ensuring data written.'''
super(FileWrapper, self).flush()
if hasattr(self.wrapped_file, 'flush'):
self.wrapped_file.flush()
def seek(self, offset, whence=os.SEEK_SET):
'''Move internal pointer by *offset*.'''
self.wrapped_file.seek(offset, whence)
def tell(self):
'''Return current position of internal pointer.'''
return self.wrapped_file.tell()
def close(self):
'''Flush buffers and prevent further access.'''
if not self.closed:
super(FileWrapper, self).close()
if hasattr(self.wrapped_file, 'close'):
self.wrapped_file.close()
class File(FileWrapper):
'''Data wrapper accepting filepath.'''
def __init__(self, path, mode='rb'):
'''Open file at *path* with *mode*.'''
file_object = open(path, mode)
super(File, self).__init__(file_object)
class String(FileWrapper):
'''Data wrapper using TemporaryFile instance.'''
def __init__(self, content=None):
'''Initialise data with *content*.'''
# Track if data is binary or not. If it is binary then read should also
# return binary.
self.is_binary = True
super(String, self).__init__(
tempfile.TemporaryFile()
)
if content is not None:
if not isinstance(content, bytes):
self.is_binary = False
content = content.encode()
self.wrapped_file.write(content)
self.wrapped_file.seek(0)
def write(self, content):
if not isinstance(content, bytes):
self.is_binary = False
content = content.encode()
super(String, self).write(
content
)
def read(self, limit=None):
content = super(String, self).read(limit)
if not self.is_binary:
content = content.decode('utf-8')
return content