Question

I’m trying to run AnsiStrings.StringReplace on a RawByteString holding a blob of data, some of which needs to be replaced. It would work, except that inside StringReplace it converts my string to a PAnsiChar, and so the search ends up bailing out as soon as it hits the first #0 byte inside the blob.

I’m looking for a routine that works just like StringReplace, but is safe to use on blobs that may contain null bytes. Does anyone know of one?

Answer 1

I’d guess the “Offending” function in StringReplace is AnsiPos->AnsiStrPos

So… I guess short of an already working solution, I’d copy/paste the StringReplace code and change AnsiPos for something else. (i.e. AnsiStrings.PosEx)

function RawByteStringReplace(const S, OldPattern, NewPattern: AnsiString;
  Flags: TReplaceFlags): AnsiString;
var
  SearchStr, Patt, NewStr: AnsiString;
  Offset: Integer;
begin
  //Removed the uppercase part...
  SearchStr := S;
  Patt := OldPattern;

  NewStr := S;
  Result := '';
  while SearchStr <> '' do
  begin
    Offset := AnsiStrings.PosEx(Patt, SearchStr);
    if Offset = 0 then
    begin
      Result := Result + NewStr;
      Break;
    end;
    Result := Result + Copy(NewStr, 1, Offset - 1) + NewPattern;
    NewStr := Copy(NewStr, Offset + Length(OldPattern), MaxInt);
    if not (rfReplaceAll in Flags) then
    begin
      Result := Result + NewStr;
      Break;
    end;
    SearchStr := Copy(SearchStr, Offset + Length(Patt), MaxInt);
  end;
end;