Pascal (Lazarus/Delphi)

REST Receive Response in Chunks

See more REST Examples

Demonstrates how to receive a REST HTTP response in chunks.

Note: This example requires Chilkat 10.1.0 or greater.

Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.FileAccess,
  Chilkat.Rest,
  Chilkat.BinData;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  rest: TRest;
  bTls: Boolean;
  port: Integer;
  bAutoReconnect: Boolean;
  statusCode: Integer;
  outputFile: string;
  fac: TFileAccess;
  bd: TBinData;
  status: Integer;

begin
  success := False;

  //  This example requires the Chilkat API to have been previously unlocked.
  //  See Global Unlock Sample for sample code.

  rest := TRest.Create;

  //  Connect to the web server
  bTls := True;
  port := 443;
  bAutoReconnect := True;
  success := rest.Connect('chilkatsoft.com',port,bTls,bAutoReconnect);
  if (success = False) then
    begin
      WriteLn(rest.LastErrorText);
      Exit;
    end;

  //  Send the request.
  //  This can be *any* kind of request: POST, GET, PUT, etc. using *any* of the Chilkat REST methods that send requests.
  //  For this example, we'll just GET a simple XML document that is about 274K in size.

  success := rest.SendReqNoBody('GET','/hamlet.xml');
  if (success = False) then
    begin
      WriteLn(rest.LastErrorText);
      Exit;
    end;

  //  Get the response header.
  statusCode := rest.ReadResponseHeader();
  if (statusCode < 0) then
    begin
      WriteLn(rest.LastErrorText);
      Exit;
    end;

  WriteLn('response status code = ' + statusCode);

  outputFile := 'c:/temp/qa_output/hamlet.xml';

  fac := TFileAccess.Create;
  success := fac.OpenForWrite(outputFile);
  if (statusCode < 0) then
    begin
      WriteLn(fac.LastErrorText);
      Exit;
    end;

  //  Get the response in chunks.
  //  (Note: There are more efficient ways to simply download a file from a web server, such as by calling Chilkat's Http.Download method.
  //  The purpose of this method is to show how to receive a response chunk-by-chunk.)
  bd := TBinData.Create;
  status := 1;
  while status = 1 do
    begin
      //  Read a minimum of 16000 bytes.
      //  Note: Because of TLS message lengths, or the possibility of the response being either compressed (gzip/deflate) or in the HTTP chunked encoding,
      //  the amount of data received in each call can be greater than the specified min size.
      //  Chilkat will return from the call as soon as it has received an amount equal to or more than the specified size,
      //  except for the very last chunk, which can be less that the min size or even 0 bytes.

      //  The status will be one of three values:
      //  -1 = error
      //  0 = received the last chunk of the response.
      //  1 = received a chunk, and more chunks are coming..

      //  The received data is *appended* to the contents of the BinData object.
      status := rest.ReadRespChunkBd(16000,bd);
      if (status >= 0) then
        begin
          WriteLn('Received chunk: ' + bd.NumBytes + ' bytes');
          fac.FileWriteBd(bd,0,0);
          bd.Clear();
        end;
    end;

  fac.FileClose();

  WriteLn('Success.');


  rest.Free;
  fac.Free;
  bd.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.