python/google/appengine/tools/devappserver2/tee.py

   1 #!/usr/bin/env python
   2 #
   3 # Copyright 2007 Google Inc.
   4 #
   5 # Licensed under the Apache License, Version 2.0 (the "License");
   6 # you may not use this file except in compliance with the License.
   7 # You may obtain a copy of the License at
   8 #
   9 #     http://www.apache.org/licenses/LICENSE-2.0
  10 #
  11 # Unless required by applicable law or agreed to in writing, software
  12 # distributed under the License is distributed on an "AS IS" BASIS,
  13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14 # See the License for the specific language governing permissions and
  15 # limitations under the License.
  16 #
  17 """A simple line-oriented "tee"."""
  18
  19
  20 import collections
  21 import threading
  22
  23
  24 class Tee(threading.Thread):
  25   """A simple line-oriented "tee".
  26
  27   This class connects two file-like objects, piping the output of one to the
  28   input of the other, and buffering the last 100 lines.
  29   """
  30
  31   _MAX_LINES = 100
  32
  33   def __init__(self, in_f, out_f):
  34     threading.Thread.__init__(self, name='Tee')
  35     self.__in = in_f
  36     self.__out = out_f
  37     self.__deque = collections.deque('', Tee._MAX_LINES)
  38
  39   def run(self):
  40     while True:
  41       line = self.__in.readline()
  42       if not line:
  43         break
  44       self.__out.write(line)
  45       self.__deque.append(line)
  46
  47   def get_buf(self):
  48     return ''.join(self.__deque)