1 2# Copyright 2016- The Android Open Source Project 3# 4# Licensed under the Apache License, Version 2.0 (the "License"); 5# you may not use this file except in compliance with the License. 6# You may obtain a copy of the License at 7# 8# http://www.apache.org/licenses/LICENSE-2.0 9# 10# Unless required by applicable law or agreed to in writing, software 11# distributed under the License is distributed on an "AS IS" BASIS, 12# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13# See the License for the specific language governing permissions and 14# limitations under the License. 15""" 16Helper module for common telnet capability to communicate with AttenuatorInstrument(s). 17 18User code shouldn't need to directly access this class. 19""" 20 21import telnetlib 22from vts.utils.python.controllers import attenuator 23 24 25def _ascii_string(uc_string): 26 return str(uc_string).encode('ASCII') 27 28 29class _TNHelper(): 30 #This is an internal helper class for Telnet+SCPI command-based instruments. 31 #It should only be used by those implemention control libraries and not by any user code 32 # directly 33 34 def __init__(self, 35 tx_cmd_separator="\n", 36 rx_cmd_separator="\n", 37 prompt=""): 38 self._tn = None 39 40 self.tx_cmd_separator = tx_cmd_separator 41 self.rx_cmd_separator = rx_cmd_separator 42 self.prompt = prompt 43 44 def open(self, host, port=23): 45 if self._tn: 46 self._tn.close() 47 48 self._tn = telnetlib.Telnet() 49 self._tn.open(host, port, 10) 50 51 def is_open(self): 52 return bool(self._tn) 53 54 def close(self): 55 if self._tn: 56 self._tn.close() 57 self._tn = None 58 59 def cmd(self, cmd_str, wait_ret=True): 60 if not isinstance(cmd_str, str): 61 raise TypeError("Invalid command string", cmd_str) 62 63 if not self.is_open(): 64 raise attenuator.InvalidOperationError( 65 "Telnet connection not open for commands") 66 67 cmd_str.strip(self.tx_cmd_separator) 68 self._tn.read_until(_ascii_string(self.prompt), 2) 69 self._tn.write(_ascii_string(cmd_str + self.tx_cmd_separator)) 70 71 if wait_ret is False: 72 return None 73 74 match_idx, match_val, ret_text = \ 75 self._tn.expect([_ascii_string("\S+"+self.rx_cmd_separator)], 1) 76 77 if match_idx == -1: 78 raise attenuator.InvalidDataError( 79 "Telnet command failed to return valid data") 80 81 ret_text = ret_text.decode() 82 ret_text = ret_text.strip(self.tx_cmd_separator + self.rx_cmd_separator 83 + self.prompt) 84 85 return ret_text 86