package bounded_buffer_adt is

  subtype byte is bit_vector(0 to 7);

  type bounded_buffer_object;  -- private

  type bounded_buffer is access bounded_buffer_object;

  function new_bounded_buffer ( size : in positive ) return bounded_buffer;
  -- creates a bounded buffer object with 'size' bytes of storage

  procedure test_empty ( variable the_bounded_buffer : in bounded_buffer;
                         is_empty : out boolean );
  -- tests whether the bounded buffer is empty (i.e., no data to read)

  procedure test_full ( variable the_bounded_buffer : in bounded_buffer;
                        is_full : out boolean );
  -- tests whether the bounded buffer is full (i.e., no data can be written)

  procedure write ( the_bounded_buffer : inout bounded_buffer;  data : in byte );
  -- if the bounded buffer is not full, writes the data
  -- if it is full, assertion violation with severity failure

  procedure read ( the_bounded_buffer : inout bounded_buffer;  data : out byte );
  -- if the bounded buffer is not empty, read the first byte of data
  -- if it is empty, assertion violation with severity failure

  --------------------------------------------------

  -- the following types are private to the ADT

  type store_array is array (natural range <>) of byte;

  type store_ptr is access store_array;

  type bounded_buffer_object is record
      byte_count : natural;
      head_index, tail_index : natural;
      store : store_ptr;
    end record bounded_buffer_object;

end package bounded_buffer_adt;