""" filewrapper.py
This file contains a FileWrapper object, the purpose of which is to
provide a file like object that can be used with httplib2.
This is currently required because httplib2 does not allow easy use of
normal file objects. It will consume a file object on the first attempt
at sending to a server. If the server requires authentication the file
object is then not in a state to be used again, causing problems.
This object also helps to get around the problem of getting progress
back from httplib2 and httplib. It is possible to provide a callback
function and a callback size.
"""
import os
class FileWrapper(file):
""" This is currently required because httplib2 does not allow easy use of
normal file objects. It will consume a file object on the first attempt
at sending to a server. If the server requires authentication the file
object is then not in a state to be used again, causing problems.
This object also helps to get around the problem of getting progress
back from httplib2 and httplib. It is possible to provide a callback
function and a callback size.
"""
def __init__(self, *args, **kwargs):
""" :param force_size: Sets a size to force the file to be read
in this sized blocks. httplib will send files
in 8192 chunks if force_size is not set.
:type force_size: int
:param callback: function to call when a percentage step is reached
:type callback: function
:param callback_size: Step (in percentage) at which callback should
be called. This must be larger than 0.
:type callback_size: int
TODO: finish implementing callback ability (not tested)
"""
file.__init__(self, *args)
# Get options
self.force_size = kwargs.get('force_size', False)
self.callback = kwargs.get('callback', None)
self.callback_percent = getattr(self, 'callback_size', 100)
# Avoid Zero division errors
if self.callback_percent == 0:
self.callback_percent = 1
# This next line may be redundant
self.initial_read_pos = self.tell()
self.file_size = os.path.getsize(self.name)
def read(self, size=-1):
""" Just like a file objects read method but will "rewind" after the
file has reached EOF.
"""
if self.force_size:
size = self.force_size
data = file.read(self, size)
if not data or size < 0 or size >= self.file_size:
self.seek(self.initial_read_pos)
try:
if size == -1:
size = len(data)
percent = int((float(size) / self.file_size) * 100)
except ZeroDivisionError:
percent = 0
if self.callback and percent % self.callback_percent == 0:
self.callback()
return data
