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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: How to make a task wait and resume ?
Date: Fri, 18 Jan 2019 11:20:40 +0100
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Date: 2019-01-18T11:20:40+01:00
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On 2019-01-18 08:59, reinert wrote:
> I suspected to be missing something :-)
> 
> In my case, a user is normally actively interacting with the actual program
> which is about treating a large sequence of images. The user can start/stop
> a task which reads in images upfront to avoid waiting time. If the computer
> is weak (small ram) he/she sometimes has to stop the reading (and the program automatically "clean" memory) and probably resume later. Hence the "synchronization" here is not with other tasks.

This looks more like a classic Ada tasking (AKA monitors):

task body Reader is
    Buffer : Stream_Element_Array (1..Size);
    Last   : Stream_Element_Offset;
    File   : File_Type;
begin
    loop
      -- accept new file, open it
      begin
         loop
            Read (File.Stream, Buffer, Last);
            -- cache portion of file in Buffer (1..Last)
            select
               accept Forget_It;
               -- close file, clean up
               exit;
            else
               null;
            end select;
          end loop;
       exception
          when End_Error =>
             -- close file
    end loop;
end Reader;

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