Pascal (Lazarus/Delphi)

REST Asynchronous Streaming Upload Simplified

See more REST Examples

This is example is simplified in that it calls FullRequestStreamAsync instead of making calls to SendReqStreamBodyAsync, ReadResponseHeader, and ReadRespBodyStr.

It demonstrates how to create and write to a stream that feeds an asynchronous upload to cloud storage. This particular example demonstrates an upload to the Azure Cloud Storage service. The same concepts apply to S3, Google Cloud, and Google Drive.

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.Rest,
  Chilkat.AuthAzureStorage,
  Chilkat.Task,
  Chilkat.Stream;

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

procedure RunDemo;
var
  success: Boolean;
  rest: TRest;
  bTls: Boolean;
  port: Integer;
  bAutoReconnect: Boolean;
  azAuth: TAuthAzureStorage;
  sendStream: TStream;
  uploadTask: TTask;
  i: Integer;
  responseStatusCode: Integer;
  responseBodyStr: string;

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 Azure Storage Blob Service
  bTls := True;
  port := 443;
  bAutoReconnect := True;
  //  In this example, the storage account name is "chilkat".
  success := rest.Connect('chilkat.blob.core.windows.net',port,bTls,bAutoReconnect);
  if (success <> True) then
    begin
      WriteLn(rest.LastErrorText);
      Exit;
    end;

  //  Provide Azure Cloud credentials for the REST call.
  azAuth := TAuthAzureStorage.Create;
  azAuth.AccessKey := 'AZURE_ACCESS_KEY';
  //  The account name used here should match the 1st part of the domain passed in the call to Connect (above).
  azAuth.Account := 'chilkat';
  azAuth.Scheme := 'SharedKey';
  azAuth.Service := 'Blob';
  //  This causes the "x-ms-version: 2021-08-06" header to be automatically added.
  azAuth.XMsVersion := '2021-08-06';
  success := rest.SetAuthAzureStorage(azAuth);

  //  Set some request headers.
  success := rest.AddHeader('x-ms-blob-content-disposition','attachment; filename="thisIsATest.txt"');
  success := rest.AddHeader('x-ms-blob-type','BlockBlob');
  success := rest.AddHeader('x-ms-meta-m1','v1');
  success := rest.AddHeader('x-ms-meta-m2','v2');

  //  Note: The application does not need to explicitly set the following
  //  headers: x-ms-date, Authorization, and Content-Length.  These headers
  //  are automatically set by Chilkat.

  sendStream := TStream.Create;

  //  Create a background thread task to upload from the stream
  //  The name of the Azure storage container is "test".
  //  After the background task is started and running in a background thread,
  //  the foreground thread will write 100 text lines of "this is a test\r\n" to the
  //  stream.
  uploadTask := rest.FullRequestStreamAsync('PUT','/test/thisIsATest.txt',sendStream);

  //  Start the task. 
  success := uploadTask.Run();

  //  The application can write to the stream, and close the stream
  //  when finished.  Whatever is written to the stream uploaded to the remote file.

  for i := 1 to 100 do
    begin
      success := sendStream.WriteString('This is a test' + #13#10);
      if (success <> True) then
        begin
          success := uploadTask.Cancel();
          uploadTask.Free;
          WriteLn('Failed to write to sendStream.');
          Exit;
        end;
    end;

  //  Close the stream to indicate no more data will be sent.
  success := sendStream.WriteClose();

  //  Make sure the uploadTask has finished.
  //  It is likely that task is already finished..
  //  Wait a max of 5 seconds..
  success := uploadTask.Wait(5000);

  //  FullRequestStreamAsync both sent the request and received the response.
  //  Check to see if the task finished properly.
  if (uploadTask.StatusInt <> 7) then
    begin
      WriteLn('Task did not end in the finished state.');
      WriteLn('Task status: ' + uploadTask.Status);
      uploadTask.Free;
      Exit;
    end;

  //  Check to see if the call to FullRequestStream in the background thread pool succeeded.
  if (uploadTask.TaskSuccess <> True) then
    begin
      //  Show what would've been the LastErrorText had FullRequestStream been called synchronously
      WriteLn(uploadTask.ResultErrorText);
      uploadTask.Free;
      Exit;
    end;

  responseStatusCode := rest.ResponseStatusCode;

  //  When successful, the Azure Storage service will respond with a 201 response code,
  //  with an empty body.  Therefore, in the success condition, the responseStr is empty.
  if (responseStatusCode = 201) then
    begin
      WriteLn('File uploaded.');
    end
  else
    begin
      //  It failed, so examine the response body, if one was returned:
      //  Given that FullRequestStream returns a string, the return value is obtained via GetResultString.
      responseBodyStr := uploadTask.GetResultString();
      WriteLn('response body (if any): ' + responseBodyStr);

      //  Examine the request/response to see what happened.
      WriteLn('response status code = ' + rest.ResponseStatusCode);
      WriteLn('response status text = ' + rest.ResponseStatusText);
      WriteLn('response header: ' + rest.ResponseHeader);
      WriteLn('---');
      WriteLn('LastRequestStartLine: ' + rest.LastRequestStartLine);
      WriteLn('LastRequestHeader: ' + rest.LastRequestHeader);
    end;


  rest.Free;
  azAuth.Free;
  sendStream.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.