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From: wayner@kama.cs.cornell.edu (Peter Wayner)
Newsgroups: comp.sys.mac.programmer
Subject: Reading Text With Pointers...
Message-ID: <50164@cornell.UUCP>
Date: 30 Dec 90 20:43:13 GMT
Sender: nobody@cornell.UUCP
Organization: Cornell Univ. CS Dept. Ithaca NY
Lines: 38

If I read in a file of text, each character fills a byte. The
problem is that the 68000 doesn't allow unalligned access, but
the 68020/30 does. What is the best way to pull of characters
one by one? 

Does the routine need to look like:

Globals: lastword:16bits
         lasthigh:boolean
         position:pointer;

function nextchar:char;

begin
if lasthigh then
 begin
   pointer:=pointer+2;
   lastword:=pointer^;
   lasthigh:=false;
   nextchar:=BAND($ff,lastword);
	{Keep the lower eightbits via a bitwise AND.}
 end
else
 begin
   lasthigh:=true;
   nextchar:=BAND($ff,BSR(lastword,8));
     {Keep the top eight bits by first shifting right 8 bits and then anding.}
  end;

end;{nextchar}


Is there a better way to do this?

-Peter
Peter Wayner   Department of Computer Science Cornell Univ. Ithaca, NY 14850
EMail:wayner@cs.cornell.edu    Office: 607-255-9202 or 255-1008
Home: 116 Oak Ave, Ithaca, NY 14850  Phone: 607-277-6678