Pascal (Lazarus/Delphi)

REST Download Bandwidth Throttle

See more REST Examples

Demonstrates how to use download bandwidth throttling with the REST API. This example will download a file from Drobox using a file stream, with a limit on the bandwidth that can be used for the transfer. 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.CkDateTime,
  Chilkat.DtObj,
  Chilkat.Socket,
  Chilkat.Stream,
  Chilkat.Rest,
  Chilkat.JsonObject;

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

procedure RunDemo;
var
  success: Boolean;
  socket: TSocket;
  maxWaitMs: Integer;
  rest: TRest;
  json: TJsonObject;
  fileStream: TStream;
  expectedStatus: Integer;
  responseStr: string;
  apiResult: string;
  jsonResult: TJsonObject;
  size: Integer;
  rev: string;
  clientModified: string;
  ckdt: TCkDateTime;
  bLocalTime: Boolean;
  dt: TDtObj;

begin
  success := False;

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

  //  A Dropbox access token should have been previously obtained.
  //  Dropbox access tokens do not expire.
  //  See Dropbox Access Token.

  //  To use bandwidth throttling, the connection should be made using the socket API.
  //  This provides numerous properties to customize the connection, such as
  //  BandwidthThrottleDown, BandwidthThrottleUp, ClientIpAddress, ClintPort, Http Proxy,
  //  KeepAlive, PreferIpv6, RequireSslCertVerify, SoRcvBuf, SoSndBuf, SoReuseAddr,
  //  SOCKS proxy, TcpNoSDelay, TlsPinSet, TlsCipherSuite, SslAllowedCiphers, etc.

  socket := TSocket.Create;
  maxWaitMs := 5000;
  success := socket.Connect('content.dropboxapi.com',443,True,maxWaitMs);
  if (success <> True) then
    begin
      WriteLn(socket.LastErrorText);
      WriteLn('Connect Fail Reason: ' + socket.ConnectFailReason);
      Exit;
    end;

  //  Set the download bandwidth throttle rate to 50000 bytes per second.
  socket.BandwidthThrottleDown := 50000;

  rest := TRest.Create;

  //  Tell the REST object to use the connected socket.
  rest.UseConnection(socket,True);

  //  The remainder of this example is identical to the example at:
  //  Dropbox Download File.

  //  Add request headers.
  rest.AddHeader('Authorization','Bearer DROPBOX_ACCESS_TOKEN');

  //  The download "parameters" are contained in JSON passed in an HTTP request header.
  //  This is the JSON indicating the file to be downloaded:
  //  { 
  //     "path": "/Homework/lit/hamlet.xml",
  //  }

  json := TJsonObject.Create;
  json.AppendString('path','/Homework/lit/hamlet.xml');
  rest.AddHeader('Dropbox-API-Arg',json.Emit());

  //  Setup a file stream for the download
  fileStream := TStream.Create;
  fileStream.SinkFile := 'qa_output/hamletFromDropbox.xml';

  //  Indicate that the call to FullRequestNoBody should send the response body
  //  to fileStream if the response status code is 200.
  //  If a non-success response status code is received, then nothing
  //  is streamed to the output file and the error response is returned by FullRequestNoBody.
  expectedStatus := 200;
  rest.SetResponseBodyStream(expectedStatus,True,fileStream);

  responseStr := rest.FullRequestNoBody('POST','/2/files/download');
  if (rest.LastMethodSuccess = False) then
    begin
      WriteLn(rest.LastErrorText);
      Exit;
    end;

  //  When successful, Dropbox responds with a 200 response code.
  if (rest.ResponseStatusCode <> 200) then
    begin
      //  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('response body (if any): ' + responseStr);
      WriteLn('---');
      WriteLn('LastRequestStartLine: ' + rest.LastRequestStartLine);
      WriteLn('LastRequestHeader: ' + rest.LastRequestHeader);
      Exit;
    end;

  //  Information about the downloaded file is also available as JSON in a response header.
  //  The "dropbox-api-result" response header contains the information.  For example:
  apiResult := rest.ResponseHdrByName('dropbox-api-result');
  WriteLn(apiResult);

  //  In this case, the pretty-formatted dropbox-api-result JSON looks like this:
  //  { 
  //    "name": "hamlet.xml",
  //    "path_lower": "/homework/lit/hamlet.xml",
  //    "path_display": "/Homework/lit/hamlet.xml",
  //    "id": "id:74FkdeNuyKAAAAAAAAAAAQ",
  //    "client_modified": "2016-06-02T23:19:00Z",
  //    "server_modified": "2016-06-02T23:19:00Z",
  //    "rev": "9482db15f",
  //    "size": 279658
  //  }

  //  Load the JSON, pretty-print it, and demonstrate how to get some values...
  jsonResult := TJsonObject.Create;
  jsonResult.EmitCompact := False;
  jsonResult.Load(apiResult);
  //  Show the JSON pretty-printed...
  WriteLn(jsonResult.Emit());

  //  Sample code to get data from the JSON response:
  size := jsonResult.IntOf('size');
  WriteLn('size = ' + size);

  rev := jsonResult.StringOf('rev');
  WriteLn('rev = ' + rev);

  clientModified := jsonResult.StringOf('client_modified');
  ckdt := TCkDateTime.Create;
  ckdt.SetFromTimestamp(clientModified);
  bLocalTime := True;
  dt := TDtObj.Create;
  ckdt.ToDtObj(bLocalTime,dt);

  WriteLn(dt.Day + '/' + dt.Month + '/' + dt.Year + ' ' + dt.Hour + ':' + dt.Minute);


  socket.Free;
  rest.Free;
  json.Free;
  fileStream.Free;
  jsonResult.Free;
  ckdt.Free;
  dt.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.