(Delphi DLL) Download Object from Google Cloud Storage

Demonstrates how to download an object from Google Cloud Storage to a file.

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

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
sbToken: HCkStringBuilder;
http: HCkHttp;
url: PWideChar;
fileData: HCkBinData;
success: Boolean;
sbErrorResponse: HCkStringBuilder;
responseCode: Integer;

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

// This example uses a previously obtained access token having permission for the 
// scope "https://www.googleapis.com/auth/cloud-platform"

// In this example, Get Google Cloud Storage OAuth2 Access Token, 
// the service account access token was saved to a text file.  This example fetches the access token from the file..
sbToken := CkStringBuilder_Create();
CkStringBuilder_LoadFile(sbToken,'qa_data/tokens/googleCloudStorageAccessToken.txt','utf-8');

// Send a GET equivalent to this curl command.

// curl -X GET \
//     -H "Authorization: Bearer [OAUTH2_TOKEN]" \
//     -o "[SAVE_TO_LOCATION]" \
//     "https://www.googleapis.com/storage/v1/b/[BUCKET_NAME]/o/[OBJECT_NAME]?alt=media"

http := CkHttp_Create();

CkHttp_putAuthToken(http,CkStringBuilder__getAsString(sbToken));

// Construct a URL to download an object named "starfish.jpg" from the "chilkat-ocean" bucket.
CkHttp_SetUrlVar(http,'bucket_name','chilkat-ocean');
CkHttp_SetUrlVar(http,'object_name','starfish.jpg');
url := 'https://www.googleapis.com/storage/v1/b/{$bucket_name}/o/{$object_name}?alt=media';

// If there is an error response, then we didn't actually download the file data,
// but instead we downloaded an error response..
fileData := CkBinData_Create();
success := CkHttp_DownloadBd(http,url,fileData);
if (success = False) then
  begin
    Memo1.Lines.Add(CkHttp__lastErrorText(http));
    Exit;
  end;

sbErrorResponse := CkStringBuilder_Create();
responseCode := CkHttp_getLastStatus(http);
if (responseCode = 401) then
  begin
    Memo1.Lines.Add('If invalid credentials, then it is likely the access token expired.');
    Memo1.Lines.Add('Your app should automatically fetch a new access token and re-try.');
  end;

if (responseCode <> 200) then
  begin
    // Get the error response
    CkStringBuilder_AppendBd(sbErrorResponse,fileData,'utf-8',0,0);
    Memo1.Lines.Add('Error response code = ' + IntToStr(responseCode));
    Memo1.Lines.Add('Error:');
    Memo1.Lines.Add(CkStringBuilder__getAsString(sbErrorResponse));
    Exit;
  end;

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

// Save the downloaded data to a file.
success := CkBinData_WriteFile(fileData,'qa_output/starfish.jpg');

CkStringBuilder_Dispose(sbToken);
CkHttp_Dispose(http);
CkBinData_Dispose(fileData);
CkStringBuilder_Dispose(sbErrorResponse);

end;