Evaluation of software components for the Flashtool

The Flashtool design describes the [automation of the deployment process] (../design/flashtool.md). To implement the described design decisions there must be evaluate several steps.

Programming language

The decision for a programming language is very important step due to the development procedure of a software. The Flashtool needs a programming language which is supported on a Linux distribution and runs on different architectures. The script languages Bash and Python was considered to be used as programming language.

Python is a script language which is easy to learn, supports interfaces to other languages (like C), has a nice syntax and provides thousands of third-party modules.

Bash is a command language interpreter and provides an own script language. It is also the GNU/Linux standard shell.

Python vs Bash

Python and Bash are both script languages which run on likely every UNIX system. Both languages must be compared on different disciplines, to decide which language fits best for the Flashtool.

Development

Python is more productive than Bash for the development processes, because it supports common programming paradigms like object-oriented programming and functional programming.

According to the design of the Flashtool the implementation will require a lot of code. To accomplish the development of the Flashtool with Bash would result in an confusing mass of Bash-scripts and would be hard to maintain.

Community

Bash and Python is often used on Linux systems and supports both a huge community and documentation. Python provides more third-party modules for several task than Bash and is a good candidate for writing lesser code to do the job.

Calling other executables

Both languages provide a mechanism to call other executables easy.

Performance

Python is really fast in handling data structures (sorting, access) and doing calculations compared to Bash.

Interfaces to other programming languages

Python provides a library which provides C compatible data types, and allows calling functions in shared libraries. This makes it possible to wrap C libraries in pure python. ((ctypes)[https://docs.python.org/2/library/ctypes.html?highlight=ctypes#module-ctypes]) There are other libraries like swig and cython to connect C and C++ with Python.

Such mechanism are not known for Bash.

Summary

Python is more suitable as programming language for the Flashtool than Bash because:

• Python is faster (organizing data structures, http requests, etc.)
• Large Python project are easier to maintain than with Bash
• Python provides a wide variety of standard and additional modules
• and can interact with C/C++ libraries.

Python Version

After deciding to use python it is important to have in mind that there are two python versions which have many differences in their API. At the beginning of the development process, the goal was to implement the Flashtool compatible to python 2.x and python 3.x. This goal was not able to be achieved for the following reasons:

• The module tarfile has issues with unicode file names when used with python 2.x. This issues did not appear in python 3.x.

• Providing python code compatible for both versions is sometimes cumbersome and extends the implementation time.

For these reasons the decision was made to use python 3.x for the Flashtool.

User interface

The Flashtool is used in a command line interface and therefore it has to provide several program parameter to trigger the different tasks.

To implement command line options we considered using getopt or argparse. The package getopt is a C-style parser and is recommend for users of the C getopt() function. The documentation for the getopt package recommend the package argparse for users who want to write less code (who doesn't?) and get better help and error messages.

The decision to take the argparse package was easy, because a implementation of the various command line parameter, which each of them will have own options, will lead to a vast number of code with the getopt package. The argparse package is easy to use and leads to clean code. Extending the argparse code with new arguments is really easy too.

Partition a block device

To partition block devices with python we considered to use blivet or pyparted.

blivet

The blivet package is used by the fedora project and according to the documentation it is easy to create partitions.

A big disadvantage of the blivet package is, that it has many dependencies to other package, which must be installed. During the evaluation process it turned out that most of the dependencies were not installed automatically with the pip installation routine. The single dependencies had to be installed by hand. There were also some difficulties to install some of the dependencies, because they only work with python 2.7 and not python 3 or above.

After failing to use the blivet package we decided to use the pyparted package.

pyparted

This package uses the libparted package. libparted is the library of the GNU parted project. The pyparted module is a good solution for the Flashtool to partition block devices. It supports all features which are given by the C library libparted.

It took about 80 lines of code to implement the functionality for the Flashtool.