Re: Exclusive file access

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Sat, 29 Aug 2015 10:31:56 +0200, Pascal Obry wrote:

> Le samedi 29 août 2015 à 09:05 +0200, Dmitry A. Kazakov a écrit :
>> I doubt that. Windows "non-ascii" file names are UTF-16. The only
>> consistent way to have them would be Wide_Wide_Text_IO with names in
>> Wide_Wide_String internally recoded to UTF-16. Does GNAT this? I 
>> didn't
>> look at the implementation, but I bet it does not. Then how would you 
>> do
>> I/O if the content is not Wide_Wide_String?
> 
> I bet you meant Wide_ instead of Wide_Wide_ above. Right?

No, I meant Wide_Wide_String.

Ada's Wide_String is legally UCS-2. Windows is UTF-16. The only full
Unicode string type is Wide_Wide_String. For an Indo-European language
there is no difference, of course.

Under Linux most applications simply ignore Ada standard and use String
encoded in UTF-8. I suppose that under Linux GNAT calmly passes String file
names as-is, i.e. as UTF-8 [*]. A conformant, but totally useless
implementation would assume names in Latin-1 and recode them into UTF-8
before passing to Linux.

GNAT under Windows is non-conformant either. I doubt it recodes UCS-2
Wide_String into UTF-16. Thus an application that uses Wide_String names
should recode names into UTF-16 first. I.e. same mess as under Linux.

A properly designed Text_IO (Unicode aware) should have used
Wide_Wide_String and/or an UTF-8 encoded string type for all file names
everywhere.

That is why I use GIO instead of Ada standard library. GIO is UTF-8 on both
Windows and Linux, which makes the applications using it portable.

------------------------------------------------------------
* Here is a program illustrating non-conformity of Linux GNAT:

with Ada.Text_IO;             use Ada.Text_IO;
with Ada.Characters.Latin_1;  use Ada.Characters.Latin_1;

procedure Test_Latin is
   File : File_Type;
begin
   Create (File, Out_File, "" & LC_A_Diaeresis);
   Close (File);
end Test_Latin;

The created file name is garbage, instead of "ä" (a-umlaut).

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de