wsd07 / libArcus

Communication library between internal components for Ultimaker software

Arcus

This library contains C++ code and Python3 bindings for creating a socket in a thread and using this socket to send and receive messages based on the Protocol Buffers library. It is designed to facilitate the communication between Cura and its backend and similar code.

Installing Protobuf

1. Be sure to have libtool installed.
2. Download protobuf >= 3.0.0 from https://github.com/google/protobuf/releases (download ZIP and unZIP at desired location, or clone the repo). The protocol buffer is used for communication between the CuraEngine and the GUI.
3. Compile protobuf from the protobuf directory: $ $ mkdir build && cd build
4. Open CMAKE GUI and disable building of tests: $ $ cmake-gui
5. $ $ make
6. $ # make install
   (Please note the #. It indicates the need of superuser, as known as root, priviliges.)
7. (In case the shared library cannot be loaded, you can try sudo ldconfig on Linux systems)

Installing Protobuf on Windows

C++

(Make sure to use the latest MinGW stable version, e.g. MinGW 4.8.1)

1. Download and install MinGW-get from http://sourceforge.net/projects/mingw/files/Installer/mingw-get/
2. With MinGW-get, install the MSYS package for MinGW
3. With MinGW-get, install msys-autogen, msys-automake, msys-libtool
4. Download ProtoBuf from https://github.com/google/protobuf (tested with version 3.0.0)
5. Extract ProtoBuf to .../MinGW/msys/1.0/local
6. Launch .../MinGW/msys/1.0/msys.bat (run as administrator!)
7. Open a terminal and navigate to .../MinGW/msys/1.0/local/protobuf-3.0.0-alpha-1
8. $ ./autogen.sh
   1. If at this point you are getting errors of missing AM_PROG_AR, you must make sure the ar.exe binary is installed and the newest stable version.
9. $ ./configure
10. $ mingw32-make
11. $ mingw32-make install

Building

To build the library, you need CMake and Protobuf installed (see below). In addition, if the Python module should be installed, you need a python interpreter available withh the sip tool installed. Only Python 3 is supported.

Building the library can be done with:

• $ mkdir build && cd build
• $ cmake ..
• $ make
• # make install

This will install to CMake's default install prefix, /usr/local. To change the prefix, set CMAKE_INSTALL_PREFIX. By default, the examples directory is also built. To disable this, set BUILD_EXAMPLES to off.

To disable building the Python bindings, set BUILD_PYTHON to OFF. They will be installed into $prefix/lib/python3.4/site-packages on Mac OSX and Windows and to $prefix/lib/python3/dist-packages on Linux. To override this directory, set PYTHON_SITE_PACKAGES_DIR .

Building the Python bindings on 64-bit Windows requires you to build with Microsoft Visual C++ since the module will fail to import if built with MinGW.

Using the Socket

The socket assumes a very simple and strict wire protocol: one 32-bit integer with a header, one 32-bit integer with the message size, one 32-bit integer with a type id then a byte array containing the message as serialized by Protobuf. The receiving side checks for these fields and will deserialize the message, after which it can be processed by the application.

To send or receive messages, the message first needs to be registered on both sides with a call to registerMessageType(). You can also register all messages from a Protobuf .proto file with a call to registerAllMessageTypes(). For the Python bindings, this is the only supported way of registering since there are no Python classses for individual message types.

The Python bindings expose the same API as the Public C++ API, except for the missing registerMessageType() and the individual messages. The Python bindings wrap the messages in a class that exposes the message's properties as Python properties, and can thus be set the same way you would set any other Python property.

The exception is repeated fields. Currently, only repeated messages are supported, which can be created through the addRepeatedMessage() method. repeatedMessageCount() will return the number of repeated messages on an object and getRepeatedMessage() will get a certain instance of a repeated message. See python/PythonMessage.h for more details.

Origin of the Name

The name Arcus is from the Roman god Arcus. This god is the roman equivalent of the goddess Iris, who is the personification of the rainbow and the messenger of the gods.

Java

There is a Java port of libArcus, which can be found here.