(Delphi ActiveX) REST Asynchronous Streaming Upload

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.

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

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
rest: TChilkatRest;
bTls: Integer;
port: Integer;
bAutoReconnect: Integer;
success: Integer;
azAuth: TChilkatAuthAzureStorage;
sendStream: TChilkatStream;
uploadTask: IChilkatTask;
i: Integer;
responseStatusCode: Integer;
responseBodyStr: WideString;

begin
// 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 Azure Storage Blob Service
bTls := 1;
port := 443;
bAutoReconnect := 1;
// In this example, the storage account name is "chilkat".
success := rest.Connect('chilkat.blob.core.windows.net',port,bTls,bAutoReconnect);
if (success <> 1) then
  begin
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;

// Provide Azure Cloud credentials for the REST call.
azAuth := TChilkatAuthAzureStorage.Create(Self);
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.ControlInterface);

// 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 := TChilkatStream.Create(Self);

// 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.SendReqStreamBodyAsync('PUT','/test/thisIsATest.txt',sendStream.ControlInterface);

// 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 <> 1) then
      begin
        success := uploadTask.Cancel();

        Memo1.Lines.Add('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);

// OK.. we've sent the file, now we need to get the response..

// Read the response header.
responseStatusCode := rest.ReadResponseHeader();
if (responseStatusCode < 0) then
  begin
    // We were unable to receive the response header.
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;

// 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
    Memo1.Lines.Add('File uploaded.');
  end
else
  begin
    // It failed, so try reading the response body.  If no response body is coming,
    // then Chilkat will know and just return an empty string.
    responseBodyStr := rest.ReadRespBodyString();
    if (rest.LastMethodSuccess = 1) then
      begin
        Memo1.Lines.Add('response body (if any): ' + responseBodyStr);
      end;

    // Examine the request/response to see what happened.
    Memo1.Lines.Add('response status code = ' + IntToStr(rest.ResponseStatusCode));
    Memo1.Lines.Add('response status text = ' + rest.ResponseStatusText);
    Memo1.Lines.Add('response header: ' + rest.ResponseHeader);
    Memo1.Lines.Add('---');
    Memo1.Lines.Add('LastRequestStartLine: ' + rest.LastRequestStartLine);
    Memo1.Lines.Add('LastRequestHeader: ' + rest.LastRequestHeader);
  end;
end;