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# -*- coding: utf-8 -*-
# _pipes.py
# Copyright (C) 2017 LEAP
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
Components for piping data on streams.
"""
from io import BytesIO
__all__ = ['TruncatedTailPipe', 'PreamblePipe']
class TruncatedTailPipe(object):
"""
Truncate the last `tail_size` bytes from the stream.
"""
def __init__(self, output=None, tail_size=16):
self.tail_size = tail_size
self.output = output or BytesIO()
self.buffer = BytesIO()
def write(self, data):
self.buffer.write(data)
if self.buffer.tell() > self.tail_size:
self._truncate_tail()
def _truncate_tail(self):
overflow_size = self.buffer.tell() - self.tail_size
self.buffer.seek(0)
self.output.write(self.buffer.read(overflow_size))
remaining = self.buffer.read()
self.buffer.seek(0)
self.buffer.write(remaining)
self.buffer.truncate()
def close(self):
return self.output
class PreamblePipe(object):
"""
Consumes data until a space is found, then calls a callback with it and
starts forwarding data to consumer returned by this callback.
"""
def __init__(self, callback):
self.callback = callback
self.preamble = BytesIO()
self.output = None
def write(self, data):
if not self.output:
self._write_preamble(data)
else:
self.output.write(data)
def _write_preamble(self, data):
if ' ' not in data:
self.preamble.write(data)
return
preamble_chunk, remaining = data.split(' ', 1)
self.preamble.write(preamble_chunk)
self.output = self.callback(self.preamble)
self.output.write(remaining)
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