dummy_serial.py

#!/usr/bin/env python
#
#   Copyright 2012 Jonas Berg
#
#   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.
#

"""

.. moduleauthor:: Jonas Berg <pyhys@users.sourceforge.net>

dummy_serial: A dummy/mock implementation of a serial port for testing purposes.

This Python file was changed (committed) at $Date: 2014-03-23 17:12:58 +0100 (Sun, 23 Mar 2014) $,
which was $Revision: 178 $.

"""

__author__  = 'Jonas Berg'
__email__   = 'pyhys@users.sourceforge.net'
__license__ = 'Apache License, Version 2.0'

__revision__  = '$Rev: 178 $'
__date__      = '$Date: 2014-03-23 17:12:58 +0100 (Sun, 23 Mar 2014) $'

import sys
import time

DEFAULT_TIMEOUT = 5
"""The default timeot value. Used if not set by the constructor."""


DEFAULT_BAUDRATE = 19200
"""The default baud rate. Used if not set by the constructor."""


VERBOSE = False
"""Set this to :const:`True` for printing the communication, and also details on the port initialization.

Might be monkey-patched in the calling test module.

"""


RESPONSES = {}
"""A dictionary of respones from the dummy serial port.

The key is the message (string) sent to the dummy serial port, and the item is the response (string)
from the dummy serial port.

Intended to be monkey-patched in the calling test module.

"""
RESPONSES['EXAMPLEMESSAGE'] = 'EXAMPLERESPONSE'


DEFAULT_RESPONSE = ''
"""Response when no matching message (key) is found in the look-up dictionary.

Might be monkey-patched in the calling test module.

"""


class Serial():
    """Dummy (mock) serial port for testing purposes.

    Mimics the behavior of a serial port as defined by the `pySerial <http://pyserial.sourceforge.net/>`_ module.

    Args:
        * port:
        * timeout:

    Note:
    As the portname argument not is used properly, only one port on :mod:`dummy_serial` can be used simultaneously.

    """

    def __init__(self, *args, **kwargs):
        self._latestWrite = ''
        self._isOpen = True
        self.port = self.initport = kwargs['port']
        try:
            self.timeout = kwargs['timeout']
        except:
            self.timeout = DEFAULT_TIMEOUT
        try:
            self.baudrate = kwargs['baudrate']
        except:
            self.baudrate = DEFAULT_BAUDRATE

        if VERBOSE:
            _print_out('\nInitializing dummy_serial')
            _print_out('dummy_serial initialization args: ' + repr(args) )
            _print_out('dummy_serial initialization kwargs: ' + repr(kwargs) + '\n')

    def __repr__(self):
        """String representation of the dummy_serial object"""
        return "{0}.{1}<id=0x{2:x}, open={3}>(port={4!r}, timeout={5!r}, latestWrite={6!r})".format(
            self.__module__,
            self.__class__.__name__,
            id(self),
            self._isOpen,
            self.port,
            self.timeout,
            self._latestWrite,
        )

    def open(self):
        """Open a (previously initialized) port on dummy_serial."""
        if VERBOSE:
            _print_out('\nOpening port on dummy_serial\n')

        if self._isOpen:
            raise IOError('The port on dummy_serial is already open')
            
        self._isOpen = True
        self.port = self.initport

    def close(self):
        """Close a port on dummy_serial."""
        if VERBOSE:
            _print_out('\nClosing port on dummy_serial\n')

        if not self._isOpen:
            raise IOError('The port on dummy_serial is already closed')
            
        self._isOpen = False
        self.port = None


    def write(self, inputdata):
        """Write to a port on dummy_serial.

        Args:
            inputdata (string/bytes): data for sending to the port on dummy_serial. Will affect the response.

        Note that for Python2, the inputdata should be a **string**. For Python3 it should be of type **bytes**.
        
        """
        if VERBOSE:
            _print_out('\nWriting to port on dummy_serial. Given:' + repr(inputdata) + '\n')
            
        if sys.version_info[0] > 2:
            if not type(inputdata) == bytes:
                raise TypeError('The input must be type bytes. Given:' + repr(inputdata))
            inputstring = str(inputdata, encoding='latin1')
        else:
            inputstring = inputdata

        if not self._isOpen:
            raise IOError('Trying to write to dummy_serial, but the port is not open. Given:' + repr(inputdata))

        self._latestWrite = inputstring


    def read(self, numberOfBytes):
        """Read from a port on dummy_serial.

        The response is dependent on what was written last to the port on dummy_serial,
        and what is defined in the :data:`RESPONSES` dictionary.

        Args:
            numberOfBytes (int): For compability with the real function. 

        Returns a **string** for Python2 and **bytes** for Python3.

        If the response is shorter than numberOfBytes, it will sleep for timeout.
        If the response is longer than numberOfBytes, it will return only numberOfBytes bytes.

        """
        if VERBOSE:
            _print_out('\nReading from port on dummy_serial (max length {!r} bytes)'.format(numberOfBytes))
        
        if numberOfBytes < 0:
            raise IOError('The numberOfBytes to read must not be negative. Given: {!r}'.format(numberOfBytes))
        
        if not self._isOpen:
            raise IOError('Trying to read from dummy_serial, but the port is not open.')

        # Do the actual reading
        try:
            response = RESPONSES[self._latestWrite]
        except:
            response = DEFAULT_RESPONSE
        
        # TODO!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
        # Adapt the behavior to better mimic the Windows behavior
        
        # Simulate the influence of numberOfBytes
        returnstring = response
        #if response == DEFAULT_RESPONSE:
            #pass
        #elif len(response) < numberOfBytes: # Wait for timeout
            #_print_out('WARNING!! The response is shorter than given numberOfBytes to read. ' + \
                #'Response: {!r} (length = {}), numberOfBytes: {}'.format( \
                #response, len(response), numberOfBytes))
            #time.sleep(self.timeout)
        #elif len(response) > numberOfBytes: # Loose trailing bytes
            #_print_out('WARNING!! The response is longer than given numberOfBytes to read. ' + \
                #'Some bytes will be lost! Response: {!r} (length = {}), numberOfBytes: {}'.format( \
                #response, len(response), numberOfBytes))
            #returnstring = response[:numberOfBytes]
        
        if VERBOSE:
            _print_out('dummy_serial latest written data: {!r}'.format(self._latestWrite))
            _print_out('dummy_serial read return data: {!r} (has length {})\n'.format(returnstring, len(returnstring)))

        if sys.version_info[0] > 2: # Convert types to make it python3 compatible
            return bytes(returnstring, encoding='latin1')
        else:
            return returnstring

def _print_out( inputstring ):
    """Print the inputstring. To make it compatible with Python2 and Python3."""
    sys.stdout.write(inputstring + '\n')