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# Copyright 2013 OpenStack Foundation
# All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import sys
class _ProgressBarBase(object):
"""A progress bar provider for a wrapped object.
Base abstract class used by specific class wrapper to show
a progress bar when the wrapped object are consumed.
:param wrapped: Object to wrap that hold data to be consumed.
:param totalsize: The total size of the data in the wrapped object.
:note: The progress will be displayed only if sys.stdout is a tty.
"""
def __init__(self, wrapped, totalsize):
self._wrapped = wrapped
self._totalsize = float(totalsize)
self._show_progress = sys.stdout.isatty() and self._totalsize != 0
self._percent = 0
def _display_progress_bar(self, size_read):
if self._show_progress:
self._percent += size_read / self._totalsize
# Output something like this: [==========> ] 49%
sys.stdout.write('\r[{0:<30}] {1:.0%}'.format(
'=' * int(round(self._percent * 29)) + '>', self._percent
))
sys.stdout.flush()
def __getattr__(self, attr):
# Forward other attribute access to the wrapped object.
return getattr(self._wrapped, attr)
class VerboseFileWrapper(_ProgressBarBase):
"""A file wrapper with a progress bar.
The file wrapper shows and advances a progress bar whenever the
wrapped file's read method is called.
"""
def read(self, *args, **kwargs):
data = self._wrapped.read(*args, **kwargs)
if data:
self._display_progress_bar(len(data))
else:
if self._show_progress:
# Break to a new line from the progress bar for incoming
# output.
sys.stdout.write('\n')
return data
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