gsh/callbacks.py

   1 # This program is free software; you can redistribute it and/or modify
   2 # it under the terms of the GNU General Public License as published by
   3 # the Free Software Foundation; either version 2 of the License, or
   4 # (at your option) any later version.
   5 #
   6 # This program is distributed in the hope that it will be useful,
   7 # but WITHOUT ANY WARRANTY; without even the implied warranty of
   8 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   9 # GNU Library General Public License for more details.
  10 #
  11 # You should have received a copy of the GNU General Public License
  12 # along with this program; if not, write to the Free Software
  13 # Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  14 #
  15 # See the COPYING file for license information.
  16 #
  17 # Copyright (c) 2008 Guillaume Chazarain <guichaz@gmail.com>
  18
  19 # Gsh uses specially crafted strings to communicate out of band data with remote
  20 # shells. This includes detecting the shell prompt, and other events to detect.
  21 # These strings are built and sent in two parts, the remote shell should send
  22 # back the concatenation of these two strings to trigger the callback. This is
  23 # to insure that the sending of the trigger to the remote shell does not trigger
  24 # the callback.
  25 #
  26 # Example: The trigger FOOBAR could be split into FOO and BAR and sent as
  27 #          echo "FOO""BAR" so that the sent string does not contain FOOBAR.
  28
  29 import random
  30
  31 DIGITS_LETTERS = map(str, range(10))                     + \
  32                  map(chr, range(ord('a'), ord('z') + 1)) + \
  33                  map(chr, range(ord('A'), ord('Z') + 1))
  34
  35 def random_string(length):
  36     def random_char():
  37         return DIGITS_LETTERS[random.randint(0, len(DIGITS_LETTERS) - 1)]
  38     return ''.join(map(lambda i: random_char(), xrange(length)))
  39
  40 COMMON_PREFIX = 'gsh-%s:' % random_string(5)
  41 NR_GENERATED_TRIGGERS = 0
  42
  43 # {'random_string()': (function, repeat)}
  44 CALLBACKS = {}
  45
  46 def add(name, function, repeat):
  47     name = name.replace('/', '_')
  48     global NR_GENERATED_TRIGGERS
  49     nr = NR_GENERATED_TRIGGERS
  50     NR_GENERATED_TRIGGERS += 1
  51     trigger = '%s%s:%s:%d/' % (COMMON_PREFIX, name, random_string(5), nr)
  52     CALLBACKS[trigger] = (function, repeat)
  53     trigger1 = trigger[:len(COMMON_PREFIX)/2]
  54     trigger2 = trigger[len(trigger1):]
  55     return trigger1, trigger2
  56
  57 def any_in(data):
  58     return COMMON_PREFIX in data
  59
  60 def process(line):
  61     start = line.find(COMMON_PREFIX)
  62     if start < 0:
  63         return False
  64
  65     end = line.find('/', start) + 1
  66     if end <= 0:
  67         return False
  68
  69     trigger = line[start:end]
  70     callback, repeat = CALLBACKS.get(trigger, (None, True))
  71     if not callback:
  72         return False
  73
  74     if not repeat:
  75         del CALLBACKS[trigger]
  76
  77     callback(line[end:].strip())
  78     return True
  79