File patchen

[jaenicke]

Zitat von kuba:

Der abgesicherte Modus ermöglicht weitreichende Manipulationsmöglichkeiten um das System zu kompromittieren.

Aber nur, wenn kein Administratorpasswort usw. gesetzt ist, denn sonst kommt man erst gar nicht ins System hinein...

Trotzdem: es ist wie gesagt ja eigentlich fast nichts zu ändern im Vergleich zu dem verlinkten ScanFile.
Hier mal eine Version, die auch für Delphi 2009 eine byteweise Ersetzung mittels AnsiStrings zulässt. 3 Zeilen und ein Parameter sind neu und eine Zeile geändert, sonst nur String durch AnsiString und PChar durch PAnsiChar ersetzt.

Delphi-Quellcode:

function ReplaceInFile(const FileName, SearchString, NewString: AnsiString;
  CaseSensitive: Boolean): Longint;
  { returns position of string in file or -1, if not found }
const
  BufferSize = $8001;  { 32K+1 bytes }
var
  pBuf, pEnd, pScan, pPos: PAnsiChar;
  filesize: LongInt;
  bytesRemaining: LongInt;
  bytesToRead: Integer;
  F: file;
  SearchFor: PAnsiChar;
  oldMode: Word;
begin
  Result := -1;  { assume failure }
  // NEW (first line): if length of string to search and new string does not match, cancel.
  // Of course one could move the rest of the file accordingly instead.
  if (Length(SearchString) <> Length(NewString))
    or (Length(SearchString) = 0) or (Length(FileName) = 0) then Exit;
  SearchFor := nil;
  pBuf      := nil;

  { open file as binary, 1 byte recordsize }
  AssignFile(F, FileName);
  oldMode  := FileMode;
  FileMode := fmOpenReadWrite;    { NEW: access to read and write }
  Reset(F, 1);
  FileMode := oldMode;
  try
    { allocate memory for buffer and pchar search string }
    SearchFor := StrAlloc(Length(SearchString) + 1);
    StrPCopy(SearchFor, SearchString);
    if not caseSensitive then  { convert to upper case }
      AnsiUpper(SearchFor);
    GetMem(pBuf, BufferSize);
    filesize       := System.Filesize(F);
    bytesRemaining := filesize;
    pPos           := nil;
    while bytesRemaining > 0 do 
    begin
      { calc how many bytes to read this round }
      if bytesRemaining >= BufferSize then
        bytesToRead := Pred(BufferSize)
      else
        bytesToRead := bytesRemaining;

      { read a buffer full and zero-terminate the buffer }
      BlockRead(F, pBuf^, bytesToRead, bytesToRead);
      pEnd  := @pBuf[bytesToRead];
      pEnd^ := #0;
       { scan the buffer. Problem: buffer may contain #0 chars! So we
         treat it as a concatenation of zero-terminated strings. }
      pScan := pBuf;
      while pScan < pEnd do 
      begin
        if not caseSensitive then { convert to upper case }
          AnsiUpper(pScan);
        pPos := StrPos(pScan, SearchFor);  { search for substring }
        if pPos <> nil then 
        begin { Found it! }
          Result := FileSize - bytesRemaining +
            Longint(pPos) - Longint(pBuf);

          // NEW: replace it
          Seek(F, Result);
          BlockWrite(F, PAnsiChar(NewString)^, Length(NewString));

          Break;
        end;
        pScan := StrEnd(pScan);
        Inc(pScan);
      end;
      if pPos <> nil then Break;
      bytesRemaining := bytesRemaining - bytesToRead;
      if bytesRemaining > 0 then 
      begin
       { no luck in this buffers load. We need to handle the case of
         the search string spanning two chunks of file now. We simply
         go back a bit in the file and read from there, thus inspecting
         some characters twice
       }
        Seek(F, FilePos(F) - Length(SearchString));
        bytesRemaining := bytesRemaining + Length(SearchString);
      end;
    end; { While }
  finally
    CloseFile(F);
    if SearchFor <> nil then StrDispose(SearchFor);
    if pBuf <> nil then FreeMem(pBuf, BufferSize);
  end;
end; { ScanFile }