Delphi DLL

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 DLL

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
rest: HCkRest;
bTls: Boolean;
port: Integer;
bAutoReconnect: Boolean;
statusCode: Integer;
outputFile: PWideChar;
fac: HCkFileAccess;
bd: HCkBinData;
status: Integer;

begin
success := False;

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

rest := CkRest_Create();

// Connect to the web server
bTls := True;
port := 443;
bAutoReconnect := True;
success := CkRest_Connect(rest,'chilkatsoft.com',port,bTls,bAutoReconnect);
if (success = False) then
  begin
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    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 := CkRest_SendReqNoBody(rest,'GET','/hamlet.xml');
if (success = False) then
  begin
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    Exit;
  end;

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

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

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

fac := CkFileAccess_Create();
success := CkFileAccess_OpenForWrite(fac,outputFile);
if (statusCode < 0) then
  begin
    Memo1.Lines.Add(CkFileAccess__lastErrorText(fac));
    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 := CkBinData_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 := CkRest_ReadRespChunkBd(rest,16000,bd);
    if (status >= 0) then
      begin
        Memo1.Lines.Add('Received chunk: ' + IntToStr(CkBinData_getNumBytes(bd)) + ' bytes');
        CkFileAccess_FileWriteBd(fac,bd,0,0);
        CkBinData_Clear(bd);
      end;
  end;

CkFileAccess_FileClose(fac);

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

CkRest_Dispose(rest);
CkFileAccess_Dispose(fac);
CkBinData_Dispose(bd);

end;