Dart

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. Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // 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.

  final socket = CkSocket();
  final maxWaitMs = 5000;
  try {
    socket.connect('content.dropboxapi.com', 443, true, maxWaitMs);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    print('Connect Fail Reason: ${socket.connectFailReason}');
    return;
  }

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

  final rest = CkRest();

  // 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",
  // }

  final json = CkJsonObject();
  json.appendString('path', '/Homework/lit/hamlet.xml');
  rest.addHeader('Dropbox-API-Arg', json.emit());

  // Setup a file stream for the download
  final fileStream = CkStream();
  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.
  final expectedStatus = 200;
  rest.setResponseBodyStream(expectedStatus, true, fileStream);

  final String responseStr;
  try {
    responseStr = rest.fullRequestNoBody('POST', '/2/files/download');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // When successful, Dropbox responds with a 200 response code.
  if (rest.responseStatusCode != 200) {
    // Examine the request/response to see what happened.
    print('response status code = ${rest.responseStatusCode}');
    print('response status text = ${rest.responseStatusText}');
    print('response header: ${rest.responseHeader}');
    print('response body (if any): $responseStr');
    print('---');
    print('LastRequestStartLine: ${rest.lastRequestStartLine}');
    print('LastRequestHeader: ${rest.lastRequestHeader}');
    return;
  }

  // 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:
  final apiResult = rest.responseHdrByName('dropbox-api-result');
  print(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...
  final jsonResult = CkJsonObject();
  jsonResult.emitCompact = false;
  jsonResult.load(apiResult);
  // Show the JSON pretty-printed...
  print(jsonResult.emit());

  // Sample code to get data from the JSON response:
  final size = jsonResult.intOf('size');
  print('size = $size');

  final rev = jsonResult.stringOf('rev');
  print('rev = $rev');

  final clientModified = jsonResult.stringOf('client_modified');
  final ckdt = CkDateTime();
  ckdt.setFromTimestamp(clientModified);
  final bLocalTime = true;
  final dt = CkDtObj();
  ckdt.toDtObj(bLocalTime, dt);

  print('${dt.day}/${dt.month}/${dt.year} ${dt.hour}:${dt.minute}');
}