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NLS thin Ada binding

#i18n #nls #bindings

This is a small Ada library that provides NLS support by using gettext (3), textdomain (3) and bindtextdomain (3).

When NLS is not supported or disabled, the Ada library implements the NLS operations by using empty suitable stubs that skip the NLS transformation and emit the English default message.

Using the library

The first step in using the NLS library is to call the Initialize procedure that handles the setup of textdomain and bindtextdomain to configure the language according to the user’s locale. The program localized messages are stored in a catalog file that is created by msginit (1) and msgfmt (1) tools. In most cases catalog file are identified by a unique name that must be given to the Initialize procedure (below, it will be mytool).

with Intl;
   PROG_NAME : constant String := "mytool";
   Intl.Initialize (PROG_NAME, "/usr/share/locale");

To localize a message, the "-" function is provided to encapsulate the call to the gettext (3) method. If the message is translated and the catalog contains it in the user’s language, it will be converted by gettext and the "-" function returns the localized message.

with GNAT.IO;
   function "-" (Message : in String) return String is (Intl."-" (Message));
   GNAT.IO.Put_Line (-("Hello world!"));

To build the message translation file (PO files), a tool can be used to extract from the source code the default messages. This process is explained in the GNU gettext documentation.