Writing a string to a TFileStream in Delphi 2010

Question

I have Delphi 2007 code that looks like this:

procedure WriteString(Stream: TFileStream; var SourceBuffer: PChar; s: string);
begin
  StrPCopy(SourceBuffer,s);
          


        

Answer 1

Delphi 2010 has a nice solution for this, documented here:

http://docwiki.embarcadero.com/CodeExamples/en/StreamStrRdWr_%28Delphi%29

var
  Writer: TStreamWriter;
...

  { Create a new stream writer directly. }
  Writer := TStreamWriter.Create('MyFile.txt', false, TEncoding.UTF8);
  Writer.Write('Some Text');

  { Close and free the writer. }
  Writer.Free();

Answer 2

You don't need a separate buffer to write a string to a stream. Probably the simplest way to do it is to encode the string to UTF8, like so:

procedure TStreamEx.writeString(const data: string);
var
   len: cardinal;
   oString: UTF8String;
begin
   oString := UTF8String(data);
   len := length(oString);
   self.WriteBuffer(len, 4);
   if len > 0 then
      self.WriteBuffer(oString[1], len);
end;

function TStreamEx.readString: string;
var
   len: integer;
   iString: UTF8String;
begin
   self.readBuffer(len, 4);
   if len > 0 then
   begin
      setLength(iString, len);
      self.ReadBuffer(iString[1], len);
      result := string(iString);
   end;
end;

I've declared TStreamEx as a class helper for TStream, but it shouldn't be too difficult to rewrite these as a solo procedure and function like your example.