Concurrent Euclid

% Bounded Buffer Monitor in Concurrent Euclid
% A classic producer-consumer synchronization example

module BoundedBuffer
  exports
    procedure deposit (item : integer)
    procedure remove (var item : integer)

  const
    bufferSize = 10

  var
    buffer : array 1 .. bufferSize of integer
    count : integer := 0
    in_ptr : integer := 1
    out_ptr : integer := 1

  procedure deposit (item : integer)
    begin
      % Wait until buffer is not full
      while count = bufferSize do
        delay
      end while

      buffer[in_ptr] := item
      in_ptr := (in_ptr mod bufferSize) + 1
      count := count + 1
    end deposit

  procedure remove (var item : integer)
    begin
      % Wait until buffer is not empty
      while count = 0 do
        delay
      end while

      item := buffer[out_ptr]
      out_ptr := (out_ptr mod bufferSize) + 1
      count := count - 1
    end remove

end BoundedBuffer