Object-oriented Software in Ada 95

298 Tasks
The implementation of the reader task is then:
with Ada.Text_Io;
use Ada.Text_Io;
package body Pack_Threads is
task body Task_Read is --Task implementation
Ch : Character;
begin
while not End_Of_File( Fd_In.all ) loop
while not End_Of_Line( Fd_In.all ) loop
Get( Fd_In.all, Ch); --Get character
P_Buffer.Put( Ch, False ); --Add to buffer
end loop;
Skip_Line( Fd_In.all ); --Next line
P_Buffer.Put( Cr, False ); --New line
end loop;
P_Buffer.Put( Eot, True ); --End of characters
accept Finish;
exception
when Tasking_Error =>
Put("Exception in Task read"); New_Line;
end Task_Read;
The rendezvous Finish is used by the reader to indicate that there is no more data.
Note: As tasking errors are not propagated beyond the task, a specific exception handler is used to detect this
eventuality.
The character constant Cr is used to indicate the newline character.
Similarly, the writer task is implemented as follows:
task body Task_Write is --Task implementation
Last : Boolean := False; --No more data
Ch : Character; --Character read
begin
loop
P_Buffer.Get( Ch, Last ); --From buffer
exit when Last;
--No more characters
if Ch = Cr then
New_Line( Fd_Out.all ); --New line
else
Put( Fd_Out.all, Ch ); --Character
end if;
end loop;
accept Finish;
--Finished
exception
when Tasking_Error =>
Put("Exception in Task write"); New_Line;
end Task_Write;
20.5.1 Barrier condition entry
The protected type uses one additional facility, that of a barrier entry. If the buffer becomes full, a mechanism is
needed to prevent further data being added. The barrier:
entry Put( Ch:in Character; No_More:in Boolean )
when No_In_Queue < Queue_Size is
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