(Delphi ActiveX) AWS S3 File Streaming Upload

Demonstrates how to do a streaming upload from a file to the AWS S3 storage service. The AWS authorization presents some difficulties when the REST request body is to be streamed from a file (or from some other source). The issue is that the SHA-256 hash of the file data must be calculated. There are only two possible ways to do this: (1) stream the file into memory in its entirety and calculate the SHA-256 hash prior to uploading, or (2) pre-calculate the SHA-256 in a streaming fashion, and then provide it to the AWS authentication object.

If the application does NOT pre-compute the SHA-256, then Chilkat (internally) is forced to stream into memory, calculate the SHA-256, and then upload from the in-memory copy of the file.

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
crypt: TChilkatCrypt2;
fileToUploadPath: WideString;
hashStr: WideString;
rest: TChilkatRest;
bTls: Integer;
port: Integer;
bAutoReconnect: Integer;
success: Integer;
authAws: TChilkatAuthAws;
fileStream: TChilkatStream;
responseStr: WideString;

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

// This first part is optional.  AWS authentication requires
// the SHA-256 hash of the request body (i.e. the contents of the file
// to be uploaded).  We can choose to pre-calculate the SHA-256 in a streaming fashion
// and then provide it to the authenticator object.  This way, if the file is
// extremely large, it never needs to completely reside in memory.
crypt := TChilkatCrypt2.Create(Self);
crypt.EncodingMode := 'hex';
crypt.HashAlgorithm := 'sha-256';
fileToUploadPath := 'qa_data/xml/hamlet.xml';
hashStr := crypt.HashFileENC(fileToUploadPath);

rest := TChilkatRest.Create(Self);

// Connect to the Amazon AWS REST server.
bTls := 1;
port := 443;
bAutoReconnect := 1;
success := rest.Connect('s3.amazonaws.com',port,bTls,bAutoReconnect);

// ----------------------------------------------------------------------------
// Important: For buckets created in regions outside us-east-1,
// there are three important changes that need to be made.
// See Working with S3 Buckets in Non-us-east-1 Regions for the details.
// ----------------------------------------------------------------------------

// Provide AWS credentials for the REST call.
authAws := TChilkatAuthAws.Create(Self);
authAws.AccessKey := 'AWS_ACCESS_KEY';
authAws.SecretKey := 'AWS_SECRET_KEY';
authAws.ServiceName := 's3';
// Provide the pre-computed SHA-256 here:
authAws.PrecomputedSha256 := hashStr;

success := rest.SetAuthAws(authAws.ControlInterface);

// Set the bucket name via the HOST header.
// In this case, the bucket name is "chilkat100".
rest.Host := 'chilkat100.s3.amazonaws.com';

fileStream := TChilkatStream.Create(Self);
fileStream.SourceFile := fileToUploadPath;

// Upload to the S3 Storage service.
// If the application provided the SHA-256 hash of the file contents (as shown above)
// then file is streamed and never has to completely reside in memory.
// If the application did NOT provide the SHA-256, then Chilkat will (internally) 
// load the entire file into memory, calculate the SHA-256, and then upload.
responseStr := rest.FullRequestStream('PUT','/hamlet.xml',fileStream.ControlInterface);
if (rest.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;

// When successful, the S3 Storage service will respond with a 200 response code,
// with an XML body.  
if (rest.ResponseStatusCode = 200) then
  begin
    Memo1.Lines.Add(responseStr);
    Memo1.Lines.Add('File uploaded.');
  end
else
  begin
    // 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('response body: ' + responseStr);
    Memo1.Lines.Add('---');
    Memo1.Lines.Add('LastRequestStartLine: ' + rest.LastRequestStartLine);
    Memo1.Lines.Add('LastRequestHeader: ' + rest.LastRequestHeader);
  end;
end;