Read the REST Response Body in Chunks

See more REST Examples

Demonstrates Rest.ReadRespChunkBd, which reads the response body one chunk at a time, appending each chunk to a BinData. A return value of 0 signals the body is complete, while -1 indicates a read failure.

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.StringBuilder,
  Chilkat.Rest,
  Chilkat.BinData;

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

procedure RunDemo;
var
  success: Boolean;
  rest: TRest;
  bTls: Boolean;
  bAutoReconnect: Boolean;
  statusCode: Integer;
  sbError: TStringBuilder;
  bdBody: TBinData;
  chunkResult: Integer;

begin
  success := False;

  rest := TRest.Create;
  bTls := True;
  bAutoReconnect := True;
  success := rest.Connect('example.com',443,bTls,bAutoReconnect);
  if (success = False) then
    begin
      WriteLn(rest.LastErrorText);
      Exit;
    end;

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

  statusCode := rest.ReadResponseHeader();
  if (statusCode < 0) then
    begin
      WriteLn(rest.LastErrorText);
      Exit;
    end;

  //  Check for the expected success status code.  If the response is not 200, the body is likely
  //  error text formatted as JSON, XML, or HTML rather than the expected content.  In that case read
  //  the body as text, report it, and return.
  if (statusCode <> 200) then
    begin
      sbError := TStringBuilder.Create;
      success := rest.ReadRespSb(sbError);
      if (success = False) then
        begin
          WriteLn(rest.LastErrorText);
          Exit;
        end;
      WriteLn('Request failed with status code ' + statusCode);
      WriteLn(sbError.GetAsString());
      Exit;
    end;

  //  The status code is 200.  Read the response body in chunks, appending each chunk to the BinData.
  //  Each call waits until at least the requested number of bytes is available, unless the response
  //  ends first.  A return value of 0 means the final bytes were returned and the body is complete;
  //  -1 indicates a read failure.
  bdBody := TBinData.Create;
  chunkResult := rest.ReadRespChunkBd(8192,bdBody);
  while chunkResult > 0 do
    begin
      chunkResult := rest.ReadRespChunkBd(8192,bdBody);
    end;

  if (chunkResult < 0) then
    begin
      WriteLn(rest.LastErrorText);
      Exit;
    end;
  WriteLn('Received ' + bdBody.NumBytes + ' bytes.');


  rest.Free;
      sbError.Free;
  bdBody.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.