The code herein is intended to solve a programming challenge problem involving creation and simulated transmission of messages with variable payloads over a network. The messages library contains the classes which hold the messages. The library is tested both with a native test framework and a google test framework. Instructions on how to build and install the source code with CMake and containerize example applications using Docker are also provided.
Assumptions:
- All messages are sent and received as a stream of binary data, with each byte containing 8 bits of message content. Bits are sent/received from MSB to LSB.
- All message fields are in Network Byte Order. The code should be agnostic to endianness.
- Please submit your header and source files only, plus the execution result print-out. Please do not submit your executable, project files, etc.
-
A hypothetical protocol used to communicate with UAVs has the following common fields:
Bits Field 16 Message ID 8 Sender ID 8 Receiver ID 32 Payload Length Variable Payload Implement a C++ class that can be used as the base class to develop specific messages later. This class should have the following features:
- Initialization of common fields.
- Access method for each and every common field.
- A virtual Send function that returns a string containing the message to be sent.
- A virtual Receive function that accepts a string containing the message received, and populates the values of the common fields.
-
Implement a C++ class using the base class above to process a message with the following payload:
Bits Field 1 Lights 1 Camera 6 Action 64 Name This class should have the following features:
- Inherits the base class in Problem #1.
- Initialization of all payload fields.
- Access method for each and every payload field.
- A Send function that returns a string containing the message to be sent.
- A Receive function that accepts a string containing the message received, and populate the values of the payload fields.
-
Write a unit test framework to verify your implementation above. Use your engineering judgment on the scope of your test cases. A text print-out should be produced for the result of each test case.
This code was compiled and tested with the following two environments:
- On Win10 with g++.exe (MinGW.org GCC-6.3.0-1) 6.3.0 and CMake version 3.26.3
- In a docker container with alpine linux, where the environment and build tools are set up dynamically
NOTE: Instructions for building, installing and consuming this code is explained for the above two environments. However, the instructions may be easily adapted for other environments which support CMake as well.
If you are using Windows with MinGW: In the root directory use:
$ cmake -S . -B build -G "MinGW Makefiles"
$ cd build
$ mingw32-make
If you are using a Docker container: Build the docker container which will build the project inside a container with an alpine linux image (see ./Dockerfile):
$ docker build --no-cache -t mcimage .
NOTE: After building the project the Doxygen docs for the message library may be found in ./build/docs
If you are using Windows with MinGW: After building the source on windows with CMake, run the messagingexample executable to see example usage of the messages library classes:
$ ./build/example/messagingexample.exe
If you are using a Docker container: After building the docker container, run the messagingexample executable inside the docker container to see example usage of the messages library classes:
$ docker run --entrypoint "/bin/sh" -it mcimage
/usr/src/MessagingChallenge/build # cd example && ./messagingexample
If you are using Windows with MinGW: After building the source on windows with CMake, run the runMessagingTests executable without any arguments to run all the tests in the native test framework:
$ ./build/test/runMessagingTests.exe
If you are using a Docker container: After building the docker container, run the runMessagingTests executable inside the containerized application executable without any arguments to run all the tests in the native test framework:
$ docker run --entrypoint "/bin/sh" -it mcimage
/usr/src/MessagingChallenge/build # cd test && ./runMessagingTests
NOTE : To exit the docker container use:
/usr/src/MessagingChallenge/build/example # exit
If you are using Windows with MinGW: After building the source on windows with CMake, run the runMessagingTests executable with the --gtest flag to run all the tests in the Google test framework:
$ ./build/test/runMessagingTests.exe --gtest
If you are using a Docker container: After building the docker container, run the runMessagingTests inside the container with the --gtest flag to run all the tests in the Google test framework:
$ docker run --entrypoint "/bin/sh" -it mcimage
/usr/src/MessagingChallenge/build # cd test && ./runMessagingTests --gtest
If you are using Windows with MinGW: To install the messages library on the system at a chosen location <install_path>, first build the project into a build directory as shown above. Then navigate to the root directory of the project and use the command:
$ cmake --install build --prefix <install_path>
If you are using a Docker container: To install the messages library on the system inside the container at a chosen location <install_path>, first build the container as shown above. Then use:
$ docker run --entrypoint "/bin/sh" -it mcimage
/usr/src/MessagingChallenge/build # cmake --install . --prefix <install_path>
An example of how to consume the library is shown in the source code subdirectory consumer, which contains a separate example project which consumes the messages library as an external dependency. In ./consumer/CMakeLists.txt we see that the messages library may be found and linked to the consumer target as follows:
set(CMAKE_PREFIX_PATH "${CMAKE_SOURCE_DIR}/../install")
find_package(messages REQUIRED)
target_link_libraries(consumer PRIVATE messages::messages)
Here, the CMAKE_PREFIX_PATH must be set to the <install_path> where the messages library was installed on the system to allow find_package to finnd the messages library. For this case, it is assumed that it was installed in a subdirectory of the root ./install and the relative path from the consumer subdirectory is used.
./consumer/consumer.cpp shows how the consuming project can include the public headers of the messages library:
#include <messages/printMessage.h>
NOTE: The Consumer project may be built using similar commands as shown for the MessagingChallenge project above, issued inside the consumer subdirectory instead of the root.
The expected output of this example usage is:
--- Example usage of baseMessage Class ---
--- Sent Message ---
Message ID: 300
Sender ID: 44
Receiver ID: 6
Payload length: 40
Payload: abcde
--- Received Message ---
Message ID: 300
Sender ID: 44
Receiver ID: 6
Payload length: 40
Payload: abcde
--- Example usage of derivedMessage Class ---
--- Sent Message ---
Message ID: 65535
Sender ID: 23
Receiver ID: 255
Payload length: 72
Payload: ┐abcdefgh
Payload Details:
Lights : 1
Camera : 0
Action : 63
Name : abcdefgh
--- Received Message ---
Message ID: 65535
Sender ID: 23
Receiver ID: 255
Payload length: 72
Payload: ┐abcdefgh
Payload Details:
Lights : 1
Camera : 0
Action : 63
Name : abcdefghThe expected output of the natively run test framework is:
--- Testing Start ---
--- Testing baseMesssage Class ---
-- Test 1 :: baseMessage send and receive with known inputs --
Test 1 Run Start
--- Sent Message ---
Message ID: 10
Sender ID: 154
Receiver ID: 6
Payload length: 40
Payload: abcde
--- Received Message ---
Message ID: 10
Sender ID: 154
Receiver ID: 6
Payload length: 40
Payload: abcde
Test 1 Run Result : SUCCESSFUL.
Test 1 Run Expected Error : None
Test 1 : PASSED
-- Test 2 : baseMessage with mesaage_ID > 255 to test endian agnosticity --
Test 2 Run Start
--- Sent Message ---
Message ID: 300
Sender ID: 7
Receiver ID: 28
Payload length: 48
Payload: afgdeg
--- Received Message ---
Message ID: 300
Sender ID: 7
Receiver ID: 28
Payload length: 48
Payload: afgdeg
Test 2 Run Result : SUCCESSFUL.
Test 2 Run Expected Error : None
Test 2 : PASSED
-- Test 3 : baseMessage send and receive messsage with 0 length --
Test 3 Run Start
--- Sent Message ---
Message ID: 51
Sender ID: 66
Receiver ID: 222
Payload length: 0
Payload:
--- Received Message ---
Message ID: 51
Sender ID: 66
Receiver ID: 222
Payload length: 0
Payload:
Test 3 Run Result : SUCCESSFUL.
Test 3 Run Expected Error : None
Test 3 : PASSED
-- Test 4 : baseMessage with with payload input longer than specified length --
Test 4 Run Start
--- Sent Message ---
Message ID: 300
Sender ID: 7
Receiver ID: 28
Payload length: 48
Payload: afgdeg
--- Received Message ---
Message ID: 300
Sender ID: 7
Receiver ID: 28
Payload length: 48
Payload: afgdeg
Test 4 Run Result : SUCCESSFUL.
Test 4 Run Expected Error : None
Test 4 : PASSED
-- Test 5 : baseMessage send and receive with payload length longer than message --
Test 5 Run Start
Test 5 Run Result : FAILURE. Reason: Exception occurred during sending message :Invalid payload length. The payload length is longer than the payload provided.
Test 5 Run Expected Error : exception
Test 5 : PASSED
-- Test 6 : baseMessage send and receive random long message(1E5 bytes) random --
Test 6 Run Start
--- Sent Message ---
Message ID: 51
Sender ID: 66
Receiver ID: 222
Payload length: 800000
Payload: YjLu0asVxyAfJWhmF4ZKKaE1Avx1emTK4L0PquHevZq0YHtj0hGSKDvsTiyslKhfAbU4elfpq8X0IUK6PgYchkZSJmzkayOBPR8p...
--- Received Message ---
Message ID: 51
Sender ID: 66
Receiver ID: 222
Payload length: 800000
Payload: YjLu0asVxyAfJWhmF4ZKKaE1Avx1emTK4L0PquHevZq0YHtj0hGSKDvsTiyslKhfAbU4elfpq8X0IUK6PgYchkZSJmzkayOBPR8p...
Test 6 Run Result : SUCCESSFUL.
Test 6 Run Expected Error : None
Test 6 : PASSED
-- Test 7 : baseMessage with payload length in fractional bytes --
Test 7 Run Start
--- Sent Message ---
Message ID: 51
Sender ID: 66
Receiver ID: 222
Payload length: 1
Payload: Y
--- Received Message ---
Message ID: 51
Sender ID: 66
Receiver ID: 222
Payload length: 1
Payload: Y
Test 7 Run Result : SUCCESSFUL.
Test 7 Run Expected Error : None
Test 7 : PASSED
-- Test 8 : baseMessage send and receive short messages( <128 bytes) 100 times with random inputs --
Test 8 : PASSED
--- Testing derivedMessage Class ---
-- Test 9 : derivedMessage with known inputs --
Test 9 Run Start
--- Sent Message ---
Message ID: 1000
Sender ID: 253
Receiver ID: 255
Payload length: 72
Payload: ╖abcdefgh
--- Received Message ---
Message ID: 1000
Sender ID: 253
Receiver ID: 255
Payload length: 72
Payload: ╖abcdefgh
Payload Details:
Lights : 1
Camera : 0
Action : 55
Name : abcdefgh
Test 9 Run Result : SUCCESSFUL.
Test 9 Run Expected Error : None
Test 9 : PASSED
-- Test 10 : derivedMessage with incorrect action --
Test 10 Run Start
Test 10 Run Result : FAILURE. Reason: Exception occurred during sending message :The lights to be sent in the message must be of size 1 byte (0 or 1 in decimal).
Test 10 Run Expected Error : exception
Test 10 : PASSED
-- Test 11 : derivedMessage with incorrect camera --
Test 11 Run Start
Test 11 Run Result : FAILURE. Reason: Exception occurred during sending message :The camera to be sent in the message must be of size 1 byte (0 or 1 in decimal).
Test 11 Run Expected Error : exception
Test 11 : PASSED
-- Test 12 : derivedMessage with incorrect action --
Test 12 Run Start
Test 12 Run Result : FAILURE. Reason: Exception occurred during sending message :The action to be sent in the message must be of size 6 bytes or less (less than 63 in decimal).
Test 12 Run Expected Error : exception
Test 12 : PASSED
-- Test 13 : derivedMessage with incorrect name longer than 8 characters --
Test 13 Run Start
Test 13 Run Result : FAILURE. Reason: Exception occurred during sending message :The action to be sent in the message must be of size 6 bytes or less (less than 63 in decimal).
Test 13 Run Expected Error : exception
Test 13 : PASSED
-- Test 14 : derivedMessage with incorrect name longer than 8 characters --
Test 14 Run Start
Test 14 Run Result : FAILURE. Reason: Exception occurred during sending message :The action to be sent in the message must be of size 6 bytes or less (less than 63 in decimal).
Test 14 Run Expected Error : exception
Test 14 : PASSED
-- Test 15 : derivedMessage send and receive 100 times with random inputs --
Test 15 : PASSED
TESTS SUMMARY : 15/15 tests passed ---
--- Testing End ---NOTE: Some tests use randomly generated values and will be different every run.
The expected output of the Google test run is:
[==========] Running 15 tests from 2 test suites.
[----------] Global test environment set-up.
[----------] 8 tests from testbaseMessage
[ RUN ] testbaseMessage.baseMessageKnownInputs
[ OK ] testbaseMessage.baseMessageKnownInputs (30 ms)
[ RUN ] testbaseMessage.baseMessageIDgt255
[ OK ] testbaseMessage.baseMessageIDgt255 (15 ms)
[ RUN ] testbaseMessage.baseMessage0Length
[ OK ] testbaseMessage.baseMessage0Length (0 ms)
[ RUN ] testbaseMessage.baseMessageLongerPayloadThanSpec
[ OK ] testbaseMessage.baseMessageLongerPayloadThanSpec (12 ms)
[ RUN ] testbaseMessage.baseMessageLongerPayloadThanMessage
[ OK ] testbaseMessage.baseMessageLongerPayloadThanMessage (2 ms)
[ RUN ] testbaseMessage.baseMessagereallylongmessage
[ OK ] testbaseMessage.baseMessagereallylongmessage (10 ms)
[ RUN ] testbaseMessage.baseMessagePayloadLenFractionalbyte
[ OK ] testbaseMessage.baseMessagePayloadLenFractionalbyte (1 ms)
[ RUN ] testbaseMessage.baseMessageRandomInputs
[ OK ] testbaseMessage.baseMessageRandomInputs (579 ms)
[----------] 8 tests from testbaseMessage (652 ms total)
[----------] 7 tests from testderivedMessage
[ RUN ] testderivedMessage.derivedMessageKnownInputs
[ OK ] testderivedMessage.derivedMessageKnownInputs (13 ms)
[ RUN ] testderivedMessage.derivedMessageIncorrectLights
[ OK ] testderivedMessage.derivedMessageIncorrectLights (0 ms)
[ RUN ] testderivedMessage.derivedMessageIncorrectCamera
[ OK ] testderivedMessage.derivedMessageIncorrectCamera (0 ms)
[ RUN ] testderivedMessage.derivedMessageIncorrectAction
[ OK ] testderivedMessage.derivedMessageIncorrectAction (0 ms)
[ RUN ] testderivedMessage.derivedMessageIncorrectNameLong
[ OK ] testderivedMessage.derivedMessageIncorrectNameLong (0 ms)
[ RUN ] testderivedMessage.derivedMessageIncorrectNameShort
[ OK ] testderivedMessage.derivedMessageIncorrectNameShort (0 ms)
[ RUN ] testderivedMessage.derivedMessageRandomInputs
[ OK ] testderivedMessage.derivedMessageRandomInputs (725 ms)
[----------] 7 tests from testderivedMessage (739 ms total)
[----------] Global test environment tear-down
[==========] 15 tests from 2 test suites ran. (1392 ms total)
[ PASSED ] 15 tests.