Delphi ActiveX

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.

Delphi ActiveX

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Integer;
rest: TChilkatRest;
bTls: Integer;
port: Integer;
bAutoReconnect: Integer;
statusCode: Integer;
outputFile: WideString;
fac: TCkFileAccess;
bd: TChilkatBinData;
status: Integer;

begin
success := 0;

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

rest := TChilkatRest.Create(Self);

// Connect to the web server
bTls := 1;
port := 443;
bAutoReconnect := 1;
success := rest.Connect('chilkatsoft.com',port,bTls,bAutoReconnect);
if (success = 0) then
  begin
    Memo1.Lines.Add(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 = 0) then
  begin
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;

// Get the response header.
statusCode := rest.ReadResponseHeader();
if (statusCode < 0) then
  begin
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('response status code = ' + IntToStr(statusCode));

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

fac := TCkFileAccess.Create(Self);
success := fac.OpenForWrite(outputFile);
if (statusCode < 0) then
  begin
    Memo1.Lines.Add(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 := TChilkatBinData.Create(Self);
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.ControlInterface);
    if (status >= 0) then
      begin
        Memo1.Lines.Add('Received chunk: ' + IntToStr(bd.NumBytes) + ' bytes');
        fac.FileWriteBd(bd.ControlInterface,0,0);
        bd.Clear();
      end;
  end;

fac.FileClose();

Memo1.Lines.Add('Success.');
end;