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Specman E
Interview Questions

MAILBOX

A mailbox is a communication mechanism that allows messages to be exchanged between processes. Data can be sent to a mailbox by one process and retrieved by another.

Mailbox is a built-in class that provides the following methods:
--Create a mailbox: new()
--Place a message in a mailbox: put()
--Try to place a message in a mailbox without blocking: try_put()
--Retrieve a message from a mailbox: get() or peek()
--Try to retrieve a message from a mailbox without blocking: try_get() or try_peek()
--Retrieve the number of messages in the mailbox: num()

EXAMPLE:
   program meain ;
   mailbox my_mailbox;
   initial begin
       my_mailbox = new();
       if (my_mailbox)
       begin
           fork
               put_packets();
               get_packets();
               #10000;
           join_any
       end

       #(1000);
      $display("END of Program");
   end

   task put_packets();
   integer i;
   begin
       for (i=0; i<10; i++)
       begin
           #(10);
           my_mailbox.put(i);
               $display("Done putting packet %d @time %d",i, $time);

       end
   end
   endtask

   task get_packets();
   integer i,packet;
   begin
       for (int i=0; i<10; i++)
       begin
           my_mailbox.get(packet);
           $display("Got packet %d @time %d", packet, $time);
       end
   end
   endtask
   endprogram

RESULTS:

   Done putting packet           0 @time                   10
   Got packet                    0 @time                   10
   Done putting packet           1 @time                   20
   Got packet                    1 @time                   20
   Done putting packet           2 @time                   30
   Got packet                    2 @time                   30
   Done putting packet           3 @time                   40
   Got packet                    3 @time                   40
   Done putting packet           4 @time                   50
   Got packet                    4 @time                   50
   Done putting packet           5 @time                   60
   Got packet                    5 @time                   60
   Done putting packet           6 @time                   70
   Got packet                    6 @time                   70
   Done putting packet           7 @time                   80
   Got packet                    7 @time                   80
   Done putting packet           8 @time                   90
   Got packet                    8 @time                   90
   Done putting packet           9 @time                  100
   Got packet                    9 @time                  100
   END of Program

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