From:	"A.Appleyard" <A DOT APPLEYARD AT fs2 DOT mt DOT umist DOT ac DOT uk>
To:	DJGPP AT DELORIE DOT COM
Date:	Mon, 18 Mar 1996 10:18:09 GMT
Subject:	A notation for port reads and writes in djgpp C++
Message-ID:	<5C570C5459@fs2.mt.umist.ac.uk>

If I declare these C++ classes:-
/*-----*/
class bport {public: unsigned short n; inline bport(unsigned short N){n=N;};
inline operator char(){return inportb(n);};
inline char operator=(char c){outportb(n,c); return c;};};
/*-----*/
class wport {public: unsigned int n; inline wport(unsigned int N){n=N;};
inline operator short(){return inportw(n);};
inline short operator=(short c){outportw(n,c); return c;};};
/*-----*/
class lport {public: unsigned int n; inline lport(unsigned int N){n=N;};
inline operator long(){return inportl(n);};
inline long operator=(long c){outportl(n,c); return c;};};
/*----- the value currently in port n decides what port n+1 means -----*/
class pport {public: unsigned short n; unsigned char i;
inline pport(unsigned short N,unsigned short I){n=N; i=I;};
inline operator char(){outportb(n,i); return inportb(n+1);};
inline char operator=(char c){outportw(n,(i<<8)+c); return c;};};
/*-----*/
then I can represent ports by names as if they were ordinary variables, e.g.:-
/*-----*/
char c;
bport game_control_io(0x201);  game_control_io=77; c=game_control_io;
pport bit_plane_mask(0x3c4,2); bit_plane_mask=88;  c=bit_plane_mask;
/*-----*/
and inport and outport instructions explain themselves and don't need comments.

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