package body NETWORK_PROTOCOLS is

  generic
    type BYTE is (<>) ;
    with procedure F_READ ( C : out BYTE ; 
                            EOFILE : out BOOLEAN ) ;
    with procedure F_WRITE ( C : BYTE ) ;
    with procedure RS_READ ( C : out BYTE ;
                             GOT_ONE : out BOOLEAN ;
			     RETURN_AFTER : DURATION := 0.0 ) ;
    with procedure RS_WRITE ( C : BYTE ) ;
    with procedure RS_WRITE_FLUSH ;
    with procedure SERVICE ( ABORT_TRANSFER : out BOOLEAN ) ;

  package PROTOCOL_INDEPENDENT_UTILITIES is

    type BYTE_STRING is array (INTEGER range <>) of BYTE ;

    READ_ERROR              : exception ;
    FILE_TRANSFER_ERROR     : exception ;

    function LOW_BYTE_OF_SUM ( BLOCK : BYTE_STRING ) return BYTE ;
      -- checksum algorithm used by various protocols

    procedure RS_READ_WITH_TIMEOUT ( C : out BYTE ;
                                     GOT_ONE : out BOOLEAN ;
                                     RETURN_AFTER : DURATION := 0.0 ) ;
      -- uses RS_READ to read the next byte from the RS-232 port but
      --      doesn't give up (i.e., return with GOT_ONE = TRUE) until
      --      at least RETURN_AFTER has elapsed

    procedure RS_READ_BLOCK_WITH_TIMEOUT ( Data     : in out Byte_String ;
					   Limit    : in     Duration    ;
			                   Complete :    out Boolean     ;
					   Last     :    out Integer )   ;

    procedure F_WRITE_BLOCK ( Data : in Byte_String ) ;

    procedure F_READ_BLOCK ( Data        : in out Byte_String ;
			     End_of_File :    out Boolean     ;
			     Last        :    out Integer )   ;

    procedure RS_WRITE_BLOCK ( Data : in out Byte_String ) ;

    procedure Long_Read ( Error_Cnt : in out Integer ; 
			  Hold      :    out Byte    ;
			  Errlim    : in     Integer ;
			  Limit     : in     Duration ) ;

    procedure Write_Read_With_Expected_Response ( Error_Cnt : in out Integer  ; 
						  Errlim    : in     Integer  ;
						  Hold      :    out Byte     ;
						  Write     : in     Byte     ;
						  Limit     : in     Duration ;
						  Response  : in     Byte    ) ;

    procedure Get_Byte ( Hold : out Byte ; Limit : in Duration ) ;

  end PROTOCOL_INDEPENDENT_UTILITIES ;

  package body KERMIT_PROTOCOL is separate ;
  package body XMODEM_PROTOCOL is separate ;
  
  package body GENERIC_TEXT_FILE_IO is separate ;
  package body PROTOCOL_INDEPENDENT_UTILITIES is separate ;

end NETWORK_PROTOCOLS ;