_NETWORK ACCESS TO CD-ROMs_
by John H. McCoy and Wuhsiung Lu

[LISTING ONE]

--*****************************************************
--  TYPES.ADS
--  A copyright-reserved, free use program.
--  (c)John H. McCoy, 1993
--  Sam Houston St. Univ., TX 77341-2206
--*****************************************************

with system, memory;
with unchecked_conversion;

package Types is

type byte is range 0..255;
type word is range 0..65_535;

--  The following types and functions are declared for use
--  instead of integer, and system.address to avoid "align-
--  ment holes" in record declarations.  This may not be a

--  problem with other than Meridian's implementation of ADA.

type bytes is array (word range <>) of byte;
type words is array (word range <>) of word;
subtype  W is bytes(1..2);
subtype DW is bytes(1..4);
function W_to_Word is new unchecked_conversion(W, Word);
function DW_to_SA is new unchecked_conversion(DW, system.address);
function DW_to_Long is new unchecked_conversion(DW, Long_Integer);
function Word_to_W is new unchecked_conversion(Word, W);
function SA_to_DW is new unchecked_conversion(system.address, DW);
function Long_to_DW is new unchecked_conversion(Long_Integer, DW);


subtype string8 is string(1..8);
subtype string16 is string(1..16);


function "+"(left, right: byte) return byte;
function "OR"(left, right: byte) return byte;
function "+"(left, right: word) return word;
function "OR"(left, right: word) return word;
function "+"(left, right: W) return W;
function "OR"(left, right: W) return W;

end Types;


[LISTING TWO]

--******************************************************************
--  DRIVERS.ADS     Excerpted Listing
--  A copyright-reserved, free use program.
--  (c)John H. McCoy, 1993, Sam Houston St. Univ., TX 77341-2206
--******************************************************************
with system, memory, unchecked_conversion;
with Types; use Types;

package drivers is

type DEV_CommandCodes is new byte;
   DeviceReadLong   : constant DEV_CommandCodes := 128;
type DEV_ReturnCodes is new W;
   DeviceDone   : constant DEV_ReturnCodes := Word_to_W(16#0100#);
type rhIoctlIns is record
      Status        : DEV_ReturnCodes;
      reserved      : bytes(6..13);
      MediaDesc     : byte;
      CBPtr     : DW;
      TransferCount : W;
      Start     : W;
      VolIdPtr      : DW;
   end record;
type rhXs (Command: DEV_CommandCodes := DeviceReadLong) is record
   case Command is
      when DeviceInit               =>  Init    : rhInits;
      when DeviceIoctlInput         =>  IoctlIn : rhIoctlIns;
      when DeviceIoctlOutput            =>  IoctlOut: rhIoctlOuts;
      when DeviceReadLong |
           DeviceReadLongPrefetch   =>  ReadLong: rhReadLongs;
      when DeviceSeek               =>  Seek    : rhSeeks;
      when others           =>  Other   : rhOthers;
   end case;
   end record;
type rhs is record
      Length    : byte;
      SubUnit   : byte;
      rhX       : rhXs;
   end record;          

function Rhs_to_Pkts is new unchecked_conversion(Rhs, Pkts);
function Pkts_to_Rhs is new unchecked_conversion(Pkts, Rhs);
end drivers