(Delphi ActiveX) Download Binary File to In-Memory Bytes

This example demonstrates how to download the binary content of a file from Google Drive directly into local memory.

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
success: Integer;
gAuth: TChilkatAuthGoogle;
rest: TChilkatRest;
bAutoReconnect: Integer;
gdCache: TChilkatCache;
fileId: WideString;
sbPath: TChilkatStringBuilder;
statusCode: Integer;
errResponseBody: WideString;
jpgBytes: Array of Byte;
fac: TCkFileAccess;

begin
success := 1;

// It 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 
// Google Drive scope.

gAuth := TChilkatAuthGoogle.Create(Self);
gAuth.AccessToken := 'GOOGLE-DRIVE-ACCESS-TOKEN';

rest := TChilkatRest.Create(Self);

// Connect using TLS.
// A single REST object, once connected, can be used for many Google Drive REST API calls.
// The auto-reconnect indicates that if the already-established HTTPS connection is closed,
// then it will be automatically re-established as needed.
bAutoReconnect := 1;
success := rest.Connect('www.googleapis.com',443,1,bAutoReconnect);

// Provide the authentication credentials (i.e. the access token)
rest.SetAuthGoogle(gAuth.ControlInterface);

// ------------------------------------------------------------------------------
// To download a file, we must know the file ID.
// In a previous example (see Build Local Metadata Cache
// we built a local cache to make it easy to lookup file IDs given a file path.
// Let's say we want to download "testFolder/abc/123/penguins.jpg".
// First we lookup the fileId in the cache.  With the fileId, we can download the file.
gdCache := TChilkatCache.Create(Self);
gdCache.Level := 0;
gdCache.AddRoot('C:/ckCache/googleDrive');

fileId := gdCache.FetchText('testFolder/abc/123/penguins.jpg');
if (gdCache.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add('Filepath not found in cache.');
    Exit;
  end;

// We need to send a GET request like this:
// GET https://www.googleapis.com/drive/v3/files/fileId?alt=media
// The fileId is part of the path.
sbPath := TChilkatStringBuilder.Create(Self);
sbPath.Append('/drive/v3/files/');
sbPath.Append(fileId);
rest.AddQueryParam('alt','media');

// To download to memory, we'll send the request in one call, then receive
// the response header, and then the response body.
// If the response header indicates failure or an unexpected response, then the
// body is not the data we desire.

// First send the HTTP request.
success := rest.SendReqNoBody('GET',sbPath.GetAsString());
if (success <> 1) then
  begin
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;

// Get the response header.
statusCode := rest.ReadResponseHeader();
if (statusCode <> 200) then
  begin
    Memo1.Lines.Add('response status code = ' + IntToStr(rest.ResponseStatusCode));
    Memo1.Lines.Add('response status text = ' + rest.ResponseStatusText);
    Memo1.Lines.Add('response header: ' + rest.ResponseHeader);

    // Read the response body (which should be error text or HTML)
    errResponseBody := rest.ReadRespBodyString();
    if (rest.LastMethodSuccess = 1) then
      begin
        Memo1.Lines.Add('response body: ' + errResponseBody);
      end;
    Exit;
  end;

// Read the response body, which should contain the file data.

jpgBytes := rest.ReadRespBodyBinary();
if (rest.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;

// Save jpgBytes to a file so we can examine the file to verify that it worked.
fac := TCkFileAccess.Create(Self);
fac.WriteEntireFile('qa_output/penguins_out.jpg',jpgBytes);

Memo1.Lines.Add('File downloaded.');
end;