Introduction ------------ There are 4 short labs and you are expected to complete them all (it will take more than a single two-hour lab session, and the assignments are not ordered by difficulty so you will get the most out of your lab time if you try to solve the labs in advance): #. Linux/Windows unicode handling of paths #. Cross-platform copy_file code (POSIX/WIN32, C++17, and Qt) #. Handling of translations (gettext / linguist) #. Numerical and date conversions (only Qt) The lab skeleton is on `Gitlab `_ and the instructions for the individual parts are below. .. warning :: These are cross-platform assignments; the gitlab repository is setup for the IDA labs - they use gcc cross-compilers and wine to run Windows programs under a Linux OS. While it is possible to use different computers (Linux, Windows with WSL, maybe MacOS, etc), it is probably easiest to use `SSH or ThinLinc `_ to access the lab environment. 1. Unicode file handling ------------------------ The standard C (and `POSIX `_) method of opening files for reading or writing is the ``fopen`` function call. The lab skeleton for this part is in the directory ``unicode``. Enter the directory and use the ``make`` command on a Linux computer; this will compile an executable called ``unicode`` which is a Linux executable running the code in ``unicode.c`` as well as a file ``unicode.exe`` which is the corresponding Windows executable. Run the executables using ``./unicode`` and ``wine unicode.exe`` (or by compiling and running the code on a Windows computer). Look at what files and output was generated. * Answer what happened before you modified the code and why? * Complete the ``my_fopen`` function to open filenames encoded in UTF-8 on Windows. Note that the printf statements might output gibberish on Wine or Windows because it does not expect UTF8-encoded content to be printed directly to the terminal. 2. Cross-platform file copying ------------------------------ There are many ways to copy files. Some better than others. One problem for writing cross-platform code for copying files is that for example POSIX does not have a function to perform this common operation (but it does have an operation to `link `_ two files). There exists OS-specific functions in Unix-like operating systems to copy files, see for example ``reflink.c`` in the lab skeleton for how to make a fast copy on the btrfs filesystem in Linux. One cross-platform method of copying a file is of course reading from one file and writing to another, but that may be slower and more verbose than it has to be especially if file permissions need to be preserved. The lab skeleton for this part is in the directory ``copy_file`` and you are expected to copy the file ``马Häst马.txt`` to destinations (win32.txt, cpp-win.txt, cpp-linux.txt, qt.txt). You may omit error checking; the makefile will compile code, try to run the files and checks if the file has been created: * Windows using the WIN32 API (``copy_file/win32.c``). Note that it has a special convention for unicode string literals ``L"马Häst马.txt"`` (that you are not allowed to use in the first lab; it creates a UTF-16 literal on Windows and a normal ``const char*`` cast to a ``long`` pointer on Linux. * Windows and Linux using standard C++17 code ``copy_file/cpp17.cpp``. * Linux using Qt ``copy_file/qt.cpp``. 3. Adding translations to a simple application ---------------------------------------------- In this lab, you will add translations to a (very) simple program using GNU gettext and Qt linguist. Start by running ``make gettext-main.c linguist-main.cpp`` and modify the files, marking strings for translation. Also update ``gettext.c``, giving the paths of the setup routines. For gettext, run ``xgettext --keyword=_ -c gettext-main.c``, which gives you a file ``messages.po``. Update the character set in it to UTF-8 using a text editor. You can then open and save the file using Qt Linguist (or a tool actually designed for GNU gettext, or a text editor since it is such a small file); add a translation for Swedish (input whatever text you like as the translation but make sure to include some code points not in the ASCII set). When you are done, run ``msgfmt --use-fuzzy messages.po`` (you should not use fuzzy strings by default, but Linguist might have marked some as fuzzy and this saves you some headache), which gives you a file ``messages.mo``; copy this to the location you set in the setup routines (see the documentation for the strings that are appended to the path you give; typically ``dirname/sv/LC_MESSAGES/DOMAIN.mo``). Run the code and make sure you get the translated output. .. note :: Gettext po and mo-files are used in very many different contexts (including software such as WordPress or Sphinx) and that there are different graphical user interfaces for performing the translations. .. note :: You need to use ``bind_textdomain_codeset`` to actually see the UTF-8 characters in your terminal later on. .. note :: A very useful command if you have difficulty finding the location to put translation files is ``strace`` .. code-block :: bash strace ./gettext |& grep [.]mo Typical output for success (new file descriptor = 3) or failure (returns -1) .. code-block :: none openat(AT_FDCWD, ".../sv/LC_MESSAGES/lab3.mo", O_RDONLY) = 3 openat(AT_FDCWD, ".../sv/LC_MESSAGES/lab3.mo", O_RDONLY) = -1 ENOENT (No such file or directory) For the second part, you will use Qt. Note that Qt is designed for GUI applications and the way translations are done might seem a little odd, but it simply boils down to passing translatable objects to a GUI widget which is associated with an application which has a translator associated with it. For this lab, it is possible to keep the ``puts`` calls, but you are free to replace them with other Qt objects if you find a solution that you like better. As for gettext, the application will usually contain logic to use settings based on the user's environment variables (or other methods for locale settings as appropriate for the operating system). But in this lab, you may hard-code the location of the machine-readable translation file (which is called ``.qm`` and is similar to gettext ``.mo`` files; a file called ``.ts`` corresponds to the ``.po`` file). To generate the ``.ts`` file, call ``lupdate Linguist.pro``. Open it in linguist and choose release in the GUI to create the ``.qm`` file (or call ``lrelease`` manually). The results should be similar to that of gettext. Which did you find easier? Note that you did not use nearly all features these libraries provide. 4. Numerical and date conversions --------------------------------- One of the problems with formatting text for the user is if your application expects textual input formatted using the standard C locale. For example, if you are writing a JSON parser containing the string ``1.2345`` and your application has called .. code-block :: cpp setlocale(LC_NUMERIC, "sv_SE.UTF8"); standard routines such as ``strtod()`` will then give an error for this. Write a simple program in C or C++ (easier, but still tricky) or Python (recommended to install packages that perform this task since the base Python does not support it). .. note :: C++20 is not available on the IDA lab systems so you need to use the C API for date functions even if you use C++. The program should reads a date and a floating point number from a constant string in the C locale (the date as output by ``LC_ALL=C date +%c``) and output this date and number using a Swedish locale (or another locale that will give different results than the C locale). There exists many different solutions to this problem, but calling ``setlocale(LC_NUMERIC, "C")`` is not an acceptable solution since it changes the locale for all threads in the program. Neither is performing the reading before ``setlocale()`` is called. For C, you are allowed to use GNU or Windows-specific extensions that deal with these problems. The following code snippet shows the expected order of function calls: .. code-block :: c setlocale(LC_ALL, "sv_SE.UTF8"); // If using C std::locale::global(std::locale("sv_SE.UTF8")); // If using C++ f = foo("1.2345", ...); d = bar("Fri Jul 5 05:04:02 2019", ...); baz(f, ...); // prints 1,234500 qux(d, ...); // prints fre 5 jul 2019 05:04:02 .. note :: While you are not allowed to use ``setlocale`` inside the program, you are allowed to use other functions that change the locale only for a single thread or manipulate the locale for a single stream or function call.