1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:
19:
20:
21:
22:
23:
24:
25:
26:
27:
28:
29:
30:
31:

var rfs,wfs:TFileStream;
var iRead,I:INTEGER;
var pIn,pOut,C1,C2:PCHAR;
var B:BYTE;
const BufSize = 16384; // 16kb Größe des Pufferfensters
begin
rfs:=tfilestream.create(sFileName,fmOpenRead or fmShareDenyWrite);
wfs:=tfilestream.create(sOutput,fmCreate);
getmem(pIn,BufSize+1);
getmem(pOut,BufSize+1);
repeat
  iRead:=RFS.READ(pIn^,BufSize);
  C1:=pIn;
  C2:=pOut;
  FOR I:=1 TO iRead DO
    BEGIN
      B := BYTE(C1^);
////////////////////
      hier Ver oder Entschlüsseln des Bytes
      ablegen des neuen Werts wieder in B
////////////////////
      C2^:= CHAR(B);
      INC(C1);
      INC(C2);
    END;
  WFS.WRITE(pOut^,iRead);
until (RFS.POSITION >= RFS.SIZE);
freemem(pOut,BufSize+1);
freemem(pIn,BufSize+1);
wfs.free;
rfs.free;