CIS332-004, CIS 332-104 (Spring 1996)
PRINCIPLES OF OPERATING SYSTEMS

Professor: Franz J. Kurfess

Home page:http://www.cis.njit.edu/franz   E-mail:franz@cis.njit.edu 

Assignment

Use the comments as guidelines to insert the code for the new task.

To test your program, type in characters; when you type `Z', the program stops.

Submission

You need to hand in a printout of your program (the Ada code, not the output)a, by Thursday, February 22nd.

You can send a mail message to Shiwen Chen, Schen@homer.njit.edu, to receive the incomplete code which you will have to complete.

Code

with TEXT_IO;
use  TEXT_IO;

procedure prodcons is
    item : CHARACTER;

    task type consumer;

    task type producer; 

--  Declare the new task

    task type buffer is
        entry start_buffer;
        entry insert(item : in CHARACTER);
		-- deposit an item in the buffer
        entry remove(item : out CHARACTER);
		-- retrieve an item from the buffer
    end buffer;

--  Create an instance of each task 
    b  : buffer;
    p  : producer;
    c  : consumer;

    task body buffer is
        n             : constant integer := 100;	-- buffer size
        count         : integer range 0..n := 0;	-- items in the buffer
        in_ch, out_ch : integer range 1..n := 1;	-- in and out indices
        bound_buf     : array(1..n) of CHARACTER;	-- the buffer
        item          : CHARACTER;			-- items are characters
    begin
        accept start_buffer do
             put_line("Starting buffer");
        end;
        put_line("Buffer is active");
        loop
            select
                when count < n =>		-- buffer is not full
                    accept insert( item: in CHARACTER ) do
                        bound_buf(in_ch) := item;
                        put_line("Item inserted into the buffer: ");
                        put(item);		-- display produced item 
                        in_ch:= (in_ch mod n) + 1;
                        count := count + 1;
                    end;
                or when count > 0 =>		-- buffer is not empty
                    accept remove(item : out CHARACTER) do
                        item := bound_buf(out_ch);
                        out_ch := (out_ch mod n) + 1;
                        count := count - 1;
                    end remove;
                or terminate;
            end select;
        end loop;
        put_line("Exiting buffer");
    end buffer;

    task body producer is
        item : CHARACTER;
    begin
        put_line("Producer is active");
        loop
            get(item);		-- read item from the keyboard
            b.insert(item);	-- put it into the buffer
            get(item);		-- read item from the keyboard
            b.insert(item);	-- put it into the buffer
            exit when item = 'Z';
         end loop;
        put_line("Exiting producer");
    end producer;


    task body consumer is

-- You need to write the code for the consumer task.
-- Each time it is invoked, the consumer task consumes TWO items.
-- Use the producer task as a guideline, and try to find
-- useful commmands in the rest of the code.
-- Everything you need is already somewhere in here,
-- you just have to put it together in the right way.


begin
    put("Producer/Consumer Problem");
    NEW_LINE;
    b.start_buffer;
end prodcons;