Subj : sorry for posting C source
To   : All
From : Jasen Betts
Date : Sun Aug 17 2003 10:29 am

Hi All.

Subj.
I missed the change from C_ECHO to PASCAL.... oops!

Here's the whole program  converted to pascal sort-of

it's not the most efficient way to do it, (ram or speed)

that would be to do a byte-by-byte comparison of the two files and to
rewrite resync to understand chracters streams... as a bonus there'd be no
line length limits that way

program diff;

const
      LENGTH= 1000;      { max line length }

type
      line      = array [0..length] of char;

procedure MyFgets(var s:line;var f:FILE);
var
space:word;
p:pchar;c,d:char;
pos:longint;
  procedure  addchar(c:char);
  begin
   p^:=c;
   inc(p);
   dec(space);
  end;

begin

 space:=length;
 p:=@s[0];
 if  eof(f) then begin s[0]:=#0; exit;end;

 while length >0 do
 begin
  if eof(f) then begin  {terminate unterminated lines}
     addchar(#10);
     break;
    end;
  blockread(f,c,1);
  if c in [#10,#13] then {handle #10#13 #13#10 #10 and #13 as EOL}
    begin
{      addchar(#10); }
      pos:=filepos(f);
      if not eof(f) then begin
        blockread(f,d,1);
        if (d=c) or not (d in [#10,#13]) then seek(f,pos);
      end;
      break;
    end;
  addchar(c);
 end;
 addchar(#0);
end;


function mystrcmp(var s,t:line):boolean; {false if lines match}
var p, q:pchar;
begin
  p:=@s[0];q:=@t[0];
  mystrcmp:=true;

  repeat
  if p^ <> q^ then exit;
  inc(p);
  inc(q);
  until p^=#0;
  mystrcmp:=p^ <> q^;

end;

procedure resync(var f1,f2:FILe ;matches:integer);

 { attempts to resynchronise two file pointers,
 ** succeeds with both pointing to the next matching line
 ** fails with poth pointing to EOF - could be considered succes.
 }

  const l1:line='';l2:line='';lc1:line='';lc2:line='';

 var

 po1,po2,pm1,pm2,pl1,pl2:longint;
 n,depth,y:integer;

begin
 po1:=filepos(f1);
 po2:=filepos(f2);

  for depth:=1 to maxint do
   begin

   { assertion: for all n,m <= depth :  line[f1,m] != line[f2,n] *
    * so read the next line from file1 and compare it with the    *
    * depth lines from file2 starting at po2                      }

  pl1:=filepos(f1);
  MyFgets(l1,f1);
   seek(f2,po2 );

   for y:=1 to depth-1 do begin

    pl2:=filepos(f2);
    MyFgets(l2,f2);
     if not MyStrcmp(l1,l2)then begin         { we have a match! }
       pm1:=filepos(f1);              { store file pointers }
       pm2:=filepos(f2);
       for n:=1 to matches  do begin { check next matches-1 lines also match }
         if n= matches then break;
         MyFgets(lc1,f1);
         MyFgets(lc2,f2);
         if MyStrcmp(lc1,lc2) then break;
         end;
       if n>=matches then begin            { success! }
         seek(f1,pl1 );
         seek(f2,pl2 );
         exit ;
         end;
       seek(f1,pm1 );   { failure: restore pointers, keep looking }
       seek(f2,pm2 );
       end;
     end;

  pl2:=filepos(f2);     { this section is a mirror image of the }
   MyFgets(l2,f2);      { section above, check for a match from }
   seek(f1,po1 );       { from the other side                   }

   for y:=1 to depth-2 do begin

    pl1:=filepos(f1);
    MyFgets(l1,f1);
     if not MyStrcmp(l1,l2) then begin
       pm1:=filepos(f1);
       pm2:=filepos(f2);
       for  n:=1 to matches do begin
         if n= matches then break;
         MyFgets(lc1,f1);
         MyFgets(lc2,f2);
         if MyStrcmp(lc1,lc2) then break;
         end;
       if(n>=matches) then begin
         seek(f1,pl1 );
         seek(f2,pl2 );
         exit;
         end;
       seek(f1,pm1 );
       seek(f2,pm2 );
       end;
     end;
   end;
end;






procedure process( s1,s2:string;context:integer);
var
f1,f2:file;
line1,line2: line;
pos1,pos2,match1,match2,matches,ld1,ld2:longint;
buf:pchar;

begin


assign(f1,s1);
reset(f1,1);
if(IOResult <> 0 ) then halt(1);
assign(f2,s2);
reset(f2,1);
 if(IOResult <> 0 ) then halt(1);

{  Can't do this in pascal-- major slow-up!
if(NULL==(buf=malloc(BUFFERSIZE))) return -3;
setvbuf(f1,buf,_IOFBF,BUFFERSIZE);
if(NULL==(buf=malloc(BUFFERSIZE))) return -3;
setvbuf(f2,buf,_IOFBF,BUFFERSIZE);
}

writeln('comparing[',s1,'] and [',s2,']');


matches:=0;
while  true do begin
  pos1:=filepos(f1);
  pos2:=filepos(f2);
  if( eof(f1) and eof(f2)) then break;
 MyFgets(line1,f1);
 MyFgets(line2,f2);

  if(MyStrcmp(line1,line2)) then begin

    seek(f1,pos1);
    seek(f2,pos2);
    resync(f1,f2,context);

    match1:=filepos(f1);
    seek(f1,pos1 );
    ld1:=0;
    while filepos(f1)<match1 do begin inc(ld1); MyFgets(line1,f1) end;

    match2:=filepos(f2);
    seek(f2,pos2 );
    ld2:=0;
    while filepos(f2)<match2 do begin inc(ld2); MyFgets(line2,f2) end;

    if(matches<> 0) then writeln ('C ',matches);
    if(ld1 <> 0 ) then writeln ('D ', ld1);
    if(ld2 <> 0 ) then
      begin
        writeln('A ',ld2);
        seek(f2,pos2 );

        while(filepos(f2)<match2) do
        begin
        MyFgets(line2,f2);
        writeln( pchar(@line2[0]));
        end;
      end;

    matches:=0;
    end
    else inc(matches);


  end;

close(f1);
close(f2);

    if matches <>0 then writeln ('C ',matches);
end;


begin
  process(paramstr(1),paramstr(2),1)
end.
*---/



 -=> Bye <=-

---
 * Origin: Entropy isn't what it used to be. (3:640/1042)

.