comp.lang.ada Google Group

Re: Atomic file creation

ro...@adalog.fr (Jean-Pierre Rosen) — Mon, 04 Jan 2010 17:12:06 UT

vlc a écrit :
I presume you are using some elementary OS like Unix, that fakes
temporary files short of having true ones... But the implementation is
free to behave as if they were true temporary files. This protects your
portability (to VMS for example, sigh of nostalgia...)

Re: Atomic file creation

spa...@nbi.dk (Jacob Sparre Andersen) — Mon, 04 Jan 2010 17:14:20 UT

If you use Debian, the POSIX packages are in "libflorist-dev" (stable)
and "libflorist2009-dev" (testing).
Greetings,
Jacob

Re: Atomic file creation

just.another.spam.acco...@googlemail.com (vlc) — Mon, 04 Jan 2010 16:45:05 UT

Well, they have names, are stored in in /tmp/ and still exist after
the call of Ada.Text_IO.Close in line 5. I actually checked this :-)

Re: Atomic file creation

ro...@adalog.fr (Jean-Pierre Rosen) — Mon, 04 Jan 2010 15:52:29 UT

vlc a écrit :
Maybe because temporary files have no names ;-)
Kidding appart, in the old time when people still knew how to write
operating systems, the notion of temporary file was supported by the OS,
and those files had really no name (as opposed to a junk name in /var/tmp).

Re: Atomic file creation

just.another.spam.acco...@googlemail.com (vlc) — Mon, 04 Jan 2010 15:07:10 UT

Looks good, but for some reason this package is not installed on my
box. I will look for it on the Internet.
Thanks a lot!

Re: Atomic file creation

spa...@nbi.dk (Jacob Sparre Andersen) — Mon, 04 Jan 2010 14:49:24 UT

POSIX.IO.Open_Or_Create (Name => [...],
Mode => [...],
Permissions => [...],
Options => POSIX.IO.Exclusive);
Greetings,
Jacob

Re: Atomic file creation

just.another.spam.acco...@googlemail.com (vlc) — Mon, 04 Jan 2010 14:45:41 UT

On Jan 4, 3:25 pm, Georg Bauhaus <rm.dash-bauh...@futureapps.de >
wrote:
The problem is that this file can also be created by other processes,
neither written by me nor in Ada. I doubt that I can convince an
application that I only have as a binary to respect something like
Ada's protected objects ...

Re: Atomic file creation

rm.dash-bauh...@futureapps.de (Georg Bauhaus) — Mon, 04 Jan 2010 14:25:35 UT

vlc schrieb:
A multitasking program can use a protected object
for this. Have all tasks perform I/O if and only if
it is their turn as decided by the queuing control of
the protected object.
Strictly speaking, O_EXCL is not C, but it is provided by Unix's
open(2) call. fopen(3), which is C, does not offer exclusive access

Re: Atomic file creation

just.another.spam.acco...@googlemail.com (vlc) — Mon, 04 Jan 2010 14:24:26 UT

I also tried something like this:
1 Ada.Text_IO.Create (Handle, Out_File);
2 declare
3 Temp_File : String := Ada.Text_IO.Name (Handle);
4 begin
5 Ada.Text_IO.Close (Handle);
6 Ada.Text_IO.Rename (Temp_File, "file");
7 Ada.Text_IO.Put_Line ("Success");
8 exception
9 when Ada.IO_Exceptions.Use_Error =>

Atomic file creation

just.another.spam.acco...@googlemail.com (vlc) — Mon, 04 Jan 2010 13:40:11 UT

Hi *,
I am looking for a way to create a file without overwriting it. A
simple approach would be:
1 if not Ada.Directories.Exists ("file") then
2 Ada.Text_IO.Create ("file");
3 end if;
But this is not completely safe as it is not atomic. A higher-priority
task e.g. could intercept my task between lines 1 and 2 and create the

Re: Package Asis.Clauses : a tiny error in comments

simon.j.wri...@mac.com (sjw) — Sun, 03 Jan 2010 21:42:06 UT

On Jan 3, 5:09 pm, Hibou57 (Yannick Duchêne)
You might also look at the 'getting involved' section of the page
Stephe pointed out.

Re: Open URLs

mail...@dmitry-kazakov.de (Dmitry A. Kazakov) — Sun, 03 Jan 2010 20:05:46 UT

The third / is a delimiter, theoretically there could be something between
file:// and /. The path might be followed by queries and fragments, see
here:
[link]

You just parse it. What is the problem, except that the number of URI
schemes is huge.
Regarding replacing %20 with SP, I am not sure if this has to be done. You

Re: Open URLs

just.another.spam.acco...@googlemail.com (vlc) — Sun, 03 Jan 2010 18:53:04 UT

Thanks. This looks quite promising!

Re: Open URLs

pas...@obry.net (Pascal Obry) — Sun, 03 Jan 2010 18:36:30 UT

Le 03/01/2010 19:17, vlc a écrit :
Not directly. After removing the file:// prefix, you can use AWS.URL.Decode.
Pascal.

Re: Open URLs

gautier_niou...@hotmail.com (Gautier write-only) — Sun, 03 Jan 2010 18:36:04 UT

What about doing successive string replacements:
"file://" -> ""
"%20" -> " "
etc.
?
Probably you need to make a "Replace_all" function using
Ada.Strings.Fixed's routines (unless it's already there), then it
should be straightforward.
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Gautier's Ada programming -- [link]