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with io_exceptions; use io_exceptions;
with machine_types; use machine_types;
with system;

with UNCHECKED_CONVERSION;

package body local_io_conf is

	-- Example implementation of local terminal I/O, stub version.
	-- The serial I/O code from the TDM configuration can be used
	-- to build an implementation of local_io that communicates with
	-- a terminal over an RS-232 connection.

	package serial_support is

		-- Borrowed from TDM configuration code.  NOTE -- if TDM is being
		-- used, no implementation of local_io may be used that would attempt
		-- to do I/O over the same serial port on the target that TDM uses.

		procedure init;
			-- Does target hardware specific initializations including
			-- programming the serial I/O ports.

		procedure put(b: byte);
			-- Loops until the output port is ready. Then, puts the byte
			-- to the serial output device.

		procedure get(b: out byte; got_byte: out boolean);
			-- Gets a byte if one is available from the serial input device.
			--
			-- NOTE: doesn't loop. Tests if input is available. If available,
			-- reads input byte and returns TRUE. Otherwise, returns FALSE
			-- immediately.  The routine below that uses this procedure just
			-- tests 'got_byte' in a tight loop, so a version that waits for
			-- a character would work as well.  The present procedure
			-- specification is used for compatibility with the TDM
			-- configuration code.

	end serial_support;

	package body serial_support is

	  procedure init is
		-- Does target hardware specific initializations including programming
		-- the serial I/O ports.
	  begin
		null;
	  end;

	  procedure put(b: byte) is
		-- Loops until the output port is ready. Then, puts the byte to the
		-- serial output device.
	  begin
		null;
	  end;


	  procedure get(b: out byte; got_byte: out boolean) is
		-- Gets a byte if one is avaiable from the serial input device.
		--
		-- NOTE: doesn't loop. Tests if input is available. If available,
		-- reads input byte and returns TRUE. Otherwise, returns FALSE
		-- immediately.
	  begin
		null;
	  end;

	end serial_support;


	procedure initialize(
			device: local_device_handle
		)
	is
	begin
		if device = DEV0 then
			serial_support.init;
		else
			raise USE_ERROR;
		end if;
	end initialize;


	procedure shutdown(
			device: local_device_handle
		)
	is
	begin
		null;
	end shutdown;


	procedure write_char(char: machine_types.byte) is
		-- Write a single character, mapping line-feeds
	begin
		serial_support.put(char);
		if char = machine_types.byte(character'pos(ascii.LF)) then
			serial_support.put(character'pos(ascii.CR));
		end if;
	end write_char;


	procedure read(
			device: local_device_handle;
			addr: system.address;
			count: in out natural
		)
	is
		-- any special character processing (e.g. backspace)
		-- could be done here...this version just reads the next
		-- character, changing CR into LF

		c, char: machine_types.byte;
		for char use at addr;

		got_char: boolean := FALSE;
		begin
			if device = DEV0 then
				if count > 0 then
					while not got_char loop
						serial_support.get(c, got_char);
					end loop;
					-- change CR into LF
					if c = byte(character'pos(ascii.cr)) then
						c := byte(character'pos(ascii.lf));
					end if;
					-- echo the character
					write_char(c);
					char := c;
					count := 1;
				else
					count := 0;
				end if;
			else
				raise USE_ERROR;
			end if;
	end read;


	procedure write(
			device: local_device_handle;
	    	addr: system.address;
			count: in out natural
		)
	is
		use machine_types;

		buf: array(1..count) of machine_types.byte;
		for buf use at addr;
	begin
		if device = DEV0 then
			for i in buf'range loop
				write_char(buf(i));
			end loop;
		else
			raise USE_ERROR;
		end if;
	end write;


end local_io_conf